CHARMVAL PROJECTFINAL REPORT

September 2001 - October 2003

Simona GagliardiSteve Grigson

October 2003

Contents

Contents 1

I CHEMICAL SELECTION 3

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 Chemical Usage Offshore . . . . . . . . . . . . . . . . . 6

3 Regulator and Industry Views . . . . . . . . . . . . . . 10

4 Surfactant Fraction Released Default Values in

the CHARM Model . . . . . . . . . . . . . . . . . . . . . . 17

5 Classification of Surfactants . . . . . . . . . . . . . . . 20

6 Chemistries Suggested . . . . . . . . . . . . . . . . . . . . 29

7 Conclusions and Recommendations . . . . . . . . . . . . 30

II EXPERIMENTAL 32

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2 Imidazoline Synthesis . . . . . . . . . . . . . . . . . . . . 35

3 Quats Synthesis . . . . . . . . . . . . . . . . . . . . . . . . 44

4 Analytical Techniques . . . . . . . . . . . . . . . . . . . 53

1

4.1 DCM extraction . . . . . . . . . . . . . . . . . . . 55

4.2 SPE extraction . . . . . . . . . . . . . . . . . . . . 58

4.3 HPLC-MS . . . . . . . . . . . . . . . . . . . . . . . . 72

5 Produced Water Analysis . . . . . . . . . . . . . . . . . 73

5.1 Calibration Curves . . . . . . . . . . . . . . . . . . 73

5.2 Preparations . . . . . . . . . . . . . . . . . . . . . . 77

5.3 Quats . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

5.4 Imidazolines . . . . . . . . . . . . . . . . . . . . . . . 93

6 Results Summary . . . . . . . . . . . . . . . . . . . . . . . 101

References 104

2

Part I

CHEMICAL SELECTION

S. Grigson

3

1 Introduction

The selection of chemistries for study in this project is proving more difficult

than anticipated, I believe for two reasons: confidentiality and the complexity

and diverse range of chemistries used. Partially for this reason I have broad-

ened the content of this report to include information on: current chemical

usage in the North Sea; the types of chemicals used; their chemistry; their

mode of action; and the application of the CHARM model. Background

chemical data has been obtained from the literature, the chemical companies

and the Internet.

It is intended that this document will form the basis for the final selection of

chemicals at the next steering group meeting.

Reasons for the Chemical Selection Exercise

The CHARM model uses an estimate of the produced water discharge con-

centrations of oilfield chemical residues to calculate the Hazard Quotient for

an oilfield production chemical. An integral parameter for some of these

calculations is the value estimated for the chemical’s octanol-water partition

coefficient (this is explained in detail in Section 4). For a number of chem-

icals this can be determined adequately using a shake-flask procedure [? ]

or an HPLC method [? ]. Many of the more hazardous oilfield chemicals

are believed to owe at least some of their properties to surfactant chemistries

contained in their formulations. However, surfactant chemicals do not (the-

oretically) give reliable Pow values and, subsequently, a number of default

values for a limited range of generic surfactant chemistries are specified for

4

use in the CHARM model. However, the chemical industry argue that the

limited range of default values do not cover the diverse range of chemistries

used and, further, no field validation data for these values are available. In

this initial stage of the project, all of the sponsors were contacted, and in

most cases visited, to obtain their views on which chemistries should be the

subject of study and field validation. Where possible the views given have

been presented in such a way as to maintain anonymity. However, I felt that

it would be useful to differentiate the views of the different parties.

Visits and Contacts with Sponsors

Following (and indeed prior to) the first steering group meeting, I visited or

contacted the following organisations:

Baker Petrolite 20/09/01 Visit

CEFAS 25/09/01 Visit

Shell 18/10/01 Visit

Statoil Norway/Dynea 31/10/01 Visit

Enterprise Oil 06/11/01 Visit

DTI, Aberdeen 06/11/01 Visit

FRS 09/11/01 Visit

T R Oil Services 09/11/01 Visit

Huntsman Surface Sciences Telephone request for info

Ondeo Nalco Telephone request for info

Texaco Email request for info

5

The objectives of the visits were as follows:

1. To see which chemicals were being used offshore and in what quantities.

2. To see which chemicals fell into the more hazardous OCNS categories.

3. To see which chemistries were of concern to the regulator (DTI) and

their advisers (CEFAS and FRS).

4. To find out the oil company’s views on chemical selection and substi-

tution, from an environmental/operational standpoint.

5. To ask the chemical companies whether their products’ chemistries

could be put into generic groups and, if yes, what these should be,

in particular those products with surfactant chemistries, for example

demulsifiers.

6. To ascertain how discharge concentrations of oilfield chemicals are cur-

rently calculated.

In addition, the MSDS data sheets for chemicals used offshore on platforms

selected by the sponsors were studied to see what information could be gained

for use in the chemical selection process.

2 Chemical Usage Offshore

The production chemical usage on 9 offshore platforms over periods ranging

from 6 months to one year during 2000/2001, were studied (data on two more

platforms have been received). Their chemical usage by category is shown

6

Table 1: Production chemical usage on seven production platforms.

Chemical Typical OCNSCategory

Platform No.

1 2 3 4 5 6 7 8 9

Anti-foaming A-E x x

Biocide B-E x x x x x x x x x

Deoiler C-E x x x

Corrosion inhibitor B/C x x x x x x x x

Defoamer C x x x x

Demulsifier B-D x x x x x x x x x

Gas treatment E x x x x x x x x x

Oxygen scavenger E x x x x x x x

Scale inhibitor E x x x x x x x x

in Table 1. As can be seen from the table, biocides, corrosion inhibitors,

demulsifiers, gas treatment and scale inhibiting chemicals are almost univer-

sally used on these platforms.

Chemicals were selected from the more hazardous B and C groupings and

tabulated (there is a voluntary agreement amongst operators that category A

chemicals, the most hazardous category, will not be used. However, Govern-

ment has always stated that the Risks involved in both the use and non-use

of these should be weighed up before these decisions are made). Chem-

icals that fell within these groups were corrosion inhibitors, demulsifiers,

defoamers, deoilers and combined corrosion/scale inhibitors (also some bio-

cides). In addition, the amounts of scale inhibitors used were also tabulated

for comparison (quantity wise) to the other groups. It is acknowledged that

7

Table 2: Chemical usage and discharge amounts per annum in kg (average amountper platform). Only category B/C chemicals shown plus scale inhibitors.

ChemicalType

OCNSCategory

Used Discharged Fractionreleased

Number ofplatformsconsidered

CorrosionInhibitor

B/C 79939 64354 0.81 7

Demulsifier B/C 66245 10943 0.17 9

Defoamers C 5650 0 0 3

Deoilers C 36360 36360 1.0 3

CI/SI B 65303 62038 0.95 1

ScaleInhibitor

E 303493 275142 0.91 6

scale inhibitors, although regarded as environmentally benign, are among

those used and discharged in the greatest quantities, relative to other oilfield

chemicals. The data is summarised in Table 21.

Table 3 shows a comparison between the tonnage of three types of oilfield

chemicals used and discharged in 1989 and 2000/01. The amounts of demul-

sifiers and scale inhibitors used has increased by an order of magnitude,

corrosion inhibitor usage has doubled. These figures should be treated with

caution, however, as they are estimates only.

The total amount of chemicals discharged in 2000/2001 is estimated at 53,000

tonnes/annum (based on total discharge data provided by the operators of

1A Safety Factor (0.1) is added to the chemical’s calculated produced water fractionreleased value when using the CHARM model. This is to account for chemical associatedwith oil droplets and silt particles present in produced water and the assumption that astate of equilibrium exists between the concentrations in the oil and water phases in thetopside process system.

8

Table 3: Comparison of the total chemical usage by category in the UK Sector ofthe North Sea, between 1989 and 2000/01. The data is based on information inTable 2 and the paper by ? ]. Installations refer to the number of installationshaving permits to discharge produced water.

Chemical Type Used(tonnes/year)

Discharged(tonnes/year)

Installations

1989

Corrosion Inhibitors 2,500 200 36

Demulsifiers 450 10 36

Scale Inhibitors 1,700 1,150 36

2000/01

Corrosion Inhibitors 5,436 4,376 68

Demulsifiers 4,505 744 68

Scale Inhibitors 20,638 18,710 68

all chemicals for three platforms multiplied by 68/3). Roughly 10% are cor-

rosion inhibitors and demulsifiers. Again, these figures are estimates only.

Table 4 shows a comparison between 1989 and 2000 of total oil, water and

chemical discharges. The theoretical concentrations of corrosion inhibitors,

scale inhibitors and demulsifiers in discharged produced water (assuming for

the purposes of the table use equals discharge) is also shown, for interest.

The data shows that although the number of installations permitted to dis-

charge oil has almost doubled, the total oil discharged has only increased by

63%, reflecting a continuing reduction in the level of oil in produced water.

In contrast, the produced water volumes have increased by some 230%, as

fields mature. Oilfield chemical discharges have also significantly increased

in the UK sector. However, the comparison between 1989 and 2000 should

9

Table 4: A comparison of oil, water and chemical discharges in the UK Sector of theNorth Sea in 1989 and 2000. Oilfield chemical levels in produced water estimatedfrom Table 2 (tonnes discharged) and Table 3 (produced water discharge amounts)(*? ]).

1989 2000

Number of installations permitted to discharge oil 36 68

Total oil discharged (tonnes) 3423 5395

Total water discharged (million tonnes) 106 244

Average oil in water content mg/kg (ppm) 32 21.5

Total production chemicals discharged (tonnes) 6,000* 53,000

Average corrosion inhibitors (ppm) in produced water - 18

Average demulsifiers (ppm) in produced water - 3

Average scale inhibitors (ppm) in produced water - 77

be taken as a very rough guide only.

For Statoil operated fields in the Norwegian sector of the North Sea, produc-

tion chemical usage has also increased steadily, from 5,000 tonnes in 1991 to

30,000 tonnes in 2000 (Aas et al, 2002).

3 Regulator and Industry Views

You may wish to read Section 4 first if you are less familiar with the cal-

culation of octanol water partition coefficients and the issues surrounding

surfactants.

• Chemistries of concern to the regulator and their scientific

advisers, and comments on chemical selection

Phylosophy

10

The regulator and their scientific advisers take a pragmatic view

of chemical regulation. For example, in the UK they see no rea-

son to ban aromatic solvents as they will partition primarily into

the crude oil and any contribution to the produced water will be

masked by water-soluble crude oil aromatics. Similarly, although

the Norwegians have concerns about the use of aromatic solvents,

this is primarily on health and safety grounds. Another exam-

ple is phenol formaldehyde polymers. These do not biodegrade

and therefore are identified by OSPARs Harmonised Pre-screening

scheme as being candidates for substitution. However, the UK

view is that this should only be enforced when a suitable alter-

native with the desired efficacy is available. These substances are

banned in Norway. In the UK a risk-based approach is favoured,

it being up to companies to justify why the chemicals they use are

safe.

Chemicals of concern

Generally those on list for temporary permission/substitution. For

these problem chemicals assurances would be needed that they

would not harm the environment. At present in the UK the chem-

ical companies provide formulations and ecotoxicity data in line

with the requirements of the HOCNF, Government is then ap-

plying OSPAR’s prescreening to identify those components which

are candidates for substitution and are informing suppliers of their

findings.

11

Chemistries raised as a potential problem are:

Polymers

Polymers with Mw > 600 are assumed not to pass through bi-

ological membranes (the figure is 700 in Denmark, however no

upper limit in Norway). This can be seen as a positive factor

as they will not bioaccumulate either. However, many polymers

have biodegradation rates of < 20%. OSPAR sees this as a nega-

tive factor, therefore these polymers are immediately marked for

substitution through the pre-screening criteria.

Surfactants

There is general agreement that all chemicals with surface-active

properties are surfactants. However, contrary to CHARM guide-

lines, OECD 117 [? ] Pow values may be acceptable for some

surfactants, providing the data looks sensible. One chemical sup-

plier commented that OECD 107 (shake-flask method) [? ] can

provide sensible Pow data for high molecular weight surfactants.

The solvents can be removed at 100 oC and the residues weighed.

Defoamers

There is an interest in defoamers due to the presence of fluo-

rosilicones, which are non-biodegradable and therefore marked for

substitution.

Suggestions for chemical selection:

1. Select chemicals based on those most widely used.

12

2. Look at substances where their continued use is under pressure

due to weaknesses in the CHARM approach e.g. not those that

are easily dealt with by CHARM but those that do not fit, for

example, surfactants. The ability of CHARM to deal with surfac-

tants could conceivably be altered as the result of work from the

CHARMval project.

3. CHARM copes reasonably with the non-biodegradable substances

and just applies the relevant results as it goes along. However,

non-biodegradable substances are indicated for substitution by

OSPAR pre-screening. This pre-screening is NOT part of the

CHARM model. If evidence was found by CHARMval to support

them NOT being indicated for substitution this is something that

would need to be taken up with OSPAR via OIC.

4. Chemicals or chemistries that are most misrepresented in CHARM

and pose a significant environmental danger.

Points to note:

1. All surfactants identified as being in CHARMs ‘miscellaneous’ sur-

factant type are automatically assigned fraction released values

of 1 (i.e. assumed from the point of regulation that 100% dis-

charged). It is in the chemical industry’s interest not to have

surfactants in this grouping although it may of course still be ap-

propriate for some chemistries when further work is carried out.

2. Toxicity data is based on preparations, not at substance level. An

expert judgement is therefore made by CEFAS toxicologists as to

13

the toxicity of an oilfield chemical, based on the chemical com-

position of the preparation supplied by the chemical company.

Chemical composition consists of the CAS No, molecular weight

(or average molecular weight), weight percent and chemical de-

scription (which is sufficient for a structure to be drawn) of each

substance in a preparation. This data is supplied by chemical

companies to CEFAS, along with the Pow of each substance in a

preparation.

3. Chemicals could have a high OCNS category (A/B) but a low

RQ. This is mainly due to the different ways in which the OCNS

scheme and CHARM use Log Pow values.

4. There has been voluntary ban in the North Sea for the past 3-4

years on the use of alkyl phenol ethoxylates due to their oestro-

genic properties.

• Views of the Chemical Suppliers

Chemicals of concern

1. Anything with a low Pow (< 2 i.e. water-soluble) and a high

toxicity (for example benzalkonium QUATs and imidazolines,

which generally have EC50s in the range 0-10ppm). These two

parameters most affect the hazard quotient.

2. Ethoxylated amines/acids. These attach to fish membranes

and they drown.

3. Resins. These have low mammalian toxicity (? ]). They are

particularly effective. If banned, difficult to replace.

14

4. The Chemical Regulations do not give a definition for sur-

factants but also say that Log Pows cannot be calculated for

them. However, there may be exceptions.

5. Chemical companies are always looking for alternatives to aro-

matic solvents.

6. Water treatment chemicals used in hydrocyclones. They have

poor degradability, are cationic and toxic.

Chemicals that should be studied

1. General consensus that corrosion inhibitors and demulsifiers

are two groups that should be studied. Also flocculants and

H2Sscavengers (reaction products are not measured but could

be important environmentally).

2. General consensus that five or six demulsifier chemistries widely

used plus unique chemistries.

3. Only nonyl phenol and nonyl phenol ethoxylates are banned/not

used. Does not apply to resins, which are still used in the

North Sea (Jacques et al, 2002).

4. The selected mixture of demulsifier chemistries, which have

a high viscosity, are normally blended with suitable solvents,

such as heavy aromatic naphtha and isopropyl alcohol, to pro-

vide a liquid that pours at the lowest expected temperature.

5. The least complex chemistry to study is probably a defoamer

(solvent + defoaming agent).

6. Corrosion inhibitor chemistries are generic, simpler and better

15

understood (compared to demulsifiers). Therefore should be

studied first.

• View of the Oil Companies

Chemical selection

The oil companies use chemicals that are in OCNS categories B-E

(there is a voluntary agreement not to use chemicals in category

A). The view was expressed that expertise to make environmental

decisions on chemical selection rests with, and should come from,

the government laboratories. Their key priority is performance,

although greener chemicals will be used if equally effective. In the

UK, companies see it as up to the chemical supplier to offer alter-

native (greener) chemicals. In Norway the chemical suppliers may

actually be contractually obliged by the oil companies to develop

and offer greener alternatives. Defoamers and the reaction prod-

ucts of H2S scavengers were both highlighted for study. In Norway

there are ongoing studies on radiolabelled emulsion breakers, but

these are all laboratory based.

Chemical substitution

When asked the question: “have you had any difficulties when

substituting more hazardous chemicals in terms of performance?”

the companies responded that attempts to substitute chemicals

for those in lower OCNS categories have not worked particularly

successfully, i.e. they have not been as effective. However, al-

ternative products are tried on an ongoing basis. One company

16

had rarely substituted chemicals. When it did it was for the same

category and tonnage usage. Another company reported that the

solvents were the most frequently changed substances in a prepa-

ration. Platforms may change chemicals fairly often or have man-

aged longer term (e.g. five-year contracts) evolving around similar

chemistries.

4 Surfactant Fraction Released Default

Values in the CHARM Model

Background Information on Pow Determinations

A critical parameter used to determine the water borne component concen-

tration of an oilfield chemical is the octanol-water partition coefficient (Pow).

Pow values, or more specifically log Pow, are supplied by oilfield chemical

manufacturers/suppliers to the regulatory authorities as part of the HOCNF

process. These values were originally used to assess the theoretical potential

for a chemical to bioaccumulate in marine organisms. Chemicals with log

Pow values of > 3 and a molecular weight of < 600 are deemed likely to

bioaccumulate. These values are now often used to estimate the partitioning

of oilfield chemicals between oil and water and their ready availability has

resulted in their adoption for fraction released determinations both by chem-

ical suppliers and in the CHARM model.

Octanol-water partition coefficients are presently calculated using two dif-

ferent methods. Log Pow values in the range -2 to 4 may be directly mea-

17

sured by the OECD 107 shake-flask method [? ]. However many oilfield

chemicals contain components with Pow values greater than 4. The use of

a high-pressure liquid chromatography (HPLC)-based method (OECD 117)

extends the range of log Pow estimations from 0 to 6 [? ]. This method

exploits the relationship between an intrinsic HPLC property of a substance

and its directly measured octanol-water partition coefficient, as determined

by the shake-flask OECD 107 method. Log Pow of an analyte can be derived

from the correlation between its retention time on an HPLC column and the

retention times of standards with known Pow values.

Due to the system’s capability of separating multi-component mixtures into

a series of separated peaks, HPLC has been used to assign an average Pow

value to materials comprising a mixture of several components, including oil-

field chemicals.

For HOCNF submissions to CEFAS, the log Pow of each individual substance

in a preparation is determined. If more than one peak appears in the chro-

matogram a range of Pow values will be given which encompass the first and

last peaks. If the substance is a series of homologues, a weighted-average

may be calculated and this information provided to CEFAS.

The fraction released equation used in CHARM not only requires information

on the Pow of the individual components in an oilfield chemical formulation

but also their relative abundance. To apportion quantitative information to

the composition of the original analyte requires rigorous criteria to be met.

These are: i) that the various components in the original mixture will have

equal responses - peak area / unit mass injected - for the detector in use,

and; ii) that the detectors have a linear response for each peak over the range

18

of injection quantities being encountered.

The number of component peaks detected in a mixture and their relative

abundance will depend upon the type of HPLC detector used. The most

commonly used detectors to approximate the criteria above are the differ-

ential refractive index (DRI) detector and the ultraviolet absorption (UV)

detector. The RI detector compares the refractivity of the HPLC column

eluant containing the sample with the eluant prior to the injector. Only in

the highly unlikely event of an analyte solution having an identical refractive

index to the eluant would it not be detected. However, the magnitude of the

response is dependent on the difference between the RI of the eluant with

and without analyte, with equal concentrations of different analytes altering

the RI of the solution to differing extents. Additionally, the response of the

DRI to increasing concentrations of analytes is not normally linear. Quan-

tification of individual peaks without proper standards is therefore highly

problematical.

The response of the UV detector to a particular compound is dependent

on the material’s extinction coefficient at the detector’s wavelength and for

many compounds lacking a UV chromophore this is zero. Other analytes

with the requisite uv-absorbing molecular structure will exhibit a very wide

range of responses. These properties indicate that extreme care must be ex-

ercised in data interpretation if the UV detector, which is more sensitive and

easy-to-use than the RI detector, is being employed for the analysis.

19

The Application of CHARM to Surfactant Chemistries

The current OECD 117 method is not suitable for most surfactant chemistries.

Unfortunately, many of the oilfield chemicals in the higher (i.e. potentially

more hazardous to the environment) OCNS categories contain surfactant

chemistries. For these a number of default values have been incorporated

into the CHARM manual. However, they were derived from a very limited

data set of production chemicals and, as such, have been the subject of major

disquiet amongst the chemical suppliers, who argue that they do not cover

the diverse range of chemistries actually used. Further, no field validation

data for these values are available.

The surfactant chemistries and their default fraction released values for use

in the CHARM model is given in Table 5. The values are those given in

the CHARM Manual, Version 1.2 (updated on the 12 July 2001). All other

surfactant chemistries are automatically assigned a fraction released values

of 1, i.e. assumed 100% discharged in produced water.

5 Classification of Surfactants

The chemical suppliers were asked whether they could suggest a classification

scheme for commonly used surfactant chemistries, to enable field validation

data obtained from the project to be applied to a range of products from

different suppliers. Initially, no suggestions were received. In light of this,

information was retrieved from the Internet. In addition, the chemical con-

stituents given on MSDS sheets for a range of demulsifiers and corrosion

inhibitors were put onto a spreadsheet, along with information on their solu-

20

Table 5: CHARM Default Chemistries and Fraction Released Values for Surfac-tants.

Type of surfactant Fraction released

Quaternary amines 1.0

EO-PO Block polymer demulsifier(Ethoxylate - Propoxylate)

0.4

Imidazolines 0.1

Fatty amines 0.1

Primary amines (cationic type, C≥ 12) 0.1

Phosphate esters (anionic type, C≥ 13) 0.1

Others 1.0

bility and any available environmental information, to assist in the chemical

selection process.

General Description of Corrosion Inhibitors and Demul-

sifiers - Their Chemistry and Application

• Corrosion Inhibitors [? ]

Generally, deep oil-and gas-containing formations represent an extremely

corrosive system as a result of the simultaneous presence of mineralised

water, carbon dioxide and hydrogen sulphide, with hydrocarbons. Cor-

rosion damage can be intensified by factors such as elevated temper-

ature and pressure, sulphur present either in the elementary state or

as polysulphide, organic acids, oxygen introduced with injection water,

microbiological activity at certain stages of production, and mineral

acids that may have been used to treat strata of low permeability. Flow

21

rate is also a critical factor in the corrosion process. Corrosion occur-

ring in oil and gas systems takes various forms, e.g. general corrosion,

pitting, sulphide stress corrosion cracking, embrittlement, blistering,

corrosion fatigue, erosion-corrosion, cavitation, galvanic corrosion and

microbiological corrosion.

Types of Inhibitors

Most of the inhibitors currently used in producing wells are or-

ganic nitrogenous compounds. The basic types have long chain

hydrocarbons (usually C18) as a part of the structure.

The most frequently used inhibitors in general petroleum produc-

tion can be classified as follows:

? Amides/imidazolines

? Salts of nitrogenous molecules with carboxylic acids

? Nitrogen quaternaries

? Polyoxyalkylated amines, amides and imidazolines, and

? Nitrogen heterocyclics, and compounds containing P.S.O.

• Demulsifiers

Emulsion formation

Because of the coexistence of the oil and water in the rock strata

of oil reservoirs, the crude oil extracted from the reservoir con-

tains emulsified water. Naturally occurring emulsifying agents i.e.

asphaltenes, paraffins, resins, organic acids, metallic salts and silt,

stabilise these emulsions.

22

Problems caused by emulsions

The presence of water along with the crude oil is undesirable

because of problems directly correlated to foaming, corrosion in

pipelines and tanks, and increased volume and viscosity.

Physical description of emulsions

Macro emulsions are thermodynamically unstable, and given suf-

ficient time, will separate out naturally. However, for financial

and practical reasons the process needs to be speeded up. The

process is termed demulsification. The most widely used process

in the oil industry is chemical demulsification. The difficulty with

using emulsion breakers is that they are typically specific for site

or crude-oil type, which implies that a certain emulsion breaker

that has worked for a crude oil type A will not necessarily work

for a crude oil type B.

Theory of demulsification

Rigorous attempts have been made to correlate between demulsi-

fier performance and physical properties such as molecular struc-

ture, interfacial tension, HLB (for explanation of HLB see later),

interfacial viscosity, partition viscosity, dynamic interfacial ten-

sion, and relative solubility number. However, according to chem-

ical suppliers, it is difficult to give conclusions due to big differ-

ences exhibited by each crude oil.

Demulsifier chemistry

Early demulsifiers included Turkey red oil, sulphuric acid, sul-

23

phated castor oil, polyamines, polyhydric alcohols etc. Since the

1940s, when the technology of alkylene oxide condensation started

to evolve, almost all demulsifier products have been made up of

condensation products of ethylene, propylene and butylene oxide.

Most are alkoxylate polymers that are mainly ethoxylated and

propoxylated or both. They are macromolecules held in chains,

industrially synthesised from petroleum chemicals. Polymers used

as demulsifiers are surfactants that counteract the effect of crude

oil asphaltenes. They contain both hydrophilic and hydrophobic

groups. When added to the petroleum emulsion the polymer sur-

factant locates itself in the interface between the water and oil

molecules. The hydrophilic groups orientate themselves towards

the water whilst the hydrophobic groups orientate themselves to-

wards the oil. The best polymeric surfactants are alkoxylated

material derivatives. Because they are alkoxylated, they are con-

sidered as nonionic polymers. Sometimes a mixture of nonionic,

cationic, or anionic materials are used together, depending on the

oil characteristics. Ethoxylated nonionic surfactants are effective

multi-purpose and versatile substances. Commercial products are

obtained by reaction of ethylene oxide with a hydrophobe having

an active hydrogen group (e.g, fatty acids, alkylphenols, or fatty

alcohols) in the presence of a suitable catalyst. Commercial poly-

mer formulations are accompanied by solvents. These solvents do

not induce a chemical change in the polymer, rather, they affect

the physical properties of the polymer formulation.

24

Synthesis of Surfactant Chemistries used in

Oilfield Chemicals

Long chain fatty acids derived from natural products such as coco oil (C12-

C16), tall oil (pine oil, C18-C20) etc are often used as starting materials for

synthesising actives such as imidazolines [? ]. This results in actives contain-

ing a range of molecular weights reflecting, primarily, the alkyl chain lengths

and degree of unsaturation of the raw materials. Quaternary ammonium for-

mulations derived from tertiary Coco (and also synthetic) amines which have

been quaternerised with a reactive alkylation reagent such as benzyl chloride

or dimethyl sulphate, are used in corrosion inhibitors, biocides and as cationic

surfactants [? ]. Fatty and ether amines with alkyl chain lengths ranging from

C10-C18 may be reacted with ethylene oxide to produce a range of ethoxy-

lated fatty and ether amines containing from 2 to 15 moles of ethylene oxide

producing a range of different properties (www.tomah3.com/Documents/P-

03.pdf). Water solubility increases with addition of ethylene oxide.

EO/PO Block Copolymers used in Demulsifier Formulations

The strict definition of an EO/PO block copolymers is just EO & PO i.e.

HO − (CH2CH2)m − (CH2CH(Me)O)n − (CH2CH2O)mH

EO is hydrophilic, PO lipophilic (you need n > 5 PO groups to display

lipophilic properties). m and n can be varied to give a wide range of proper-

ties. Molecular weight goes from ≈ 1, 000 to > 10, 000 but for the oil industry

usually ≈ 4, 000.

25

The EO/PO polymers can be based on any initiator with one or more active

hydrogens. For example:

1. One active hydrogen - monofunctional alcohols, i.e. R-OH (R typically

C12-C14)

R−O − (PO)n(EO)mH

2. Two active hydrogens - glycols in water.

H − (EO)m(PO)nR− (PO)n(EO)mH

R = CH2CH2 or CH(Me)CH2

3. Three active hydrogens - e.g. glycerol

RCH2 − CHR− CH2R

R = (PO)n(EO)mH

4. Four active hydrogens e.g. ethylene diamine.

R2NCH2CH2NR2

R = (PO)n(EO)mH

etc.

With such a wide range of possible substrates it is very difficult to come

up with one generic structure. Also, although the surfactants are generally

26

capped with EO, they can sometimes be capped with PO. The PO chain has

to be > 5 PO groups to show hydrophobic properties, and it is the PO chain

that does not biodegrade (personal communication).

As this class of surfactants can have such a huge range of properties, for

example, depending on the number of EO and PO groups attached they can

range from completely water soluble to completely oil soluble (see below), it

is not sensible to have one discharge factor (0.4) as per the CHARM model.

HLB (Hydrophile-Lipophile Balance)

(www.paddocklabs.com/publications/secundum/secart41.htm)

Surfactants are often described in terms of their HLB values. A brief de-

scription of HLB follows.

The HLB (Hydrophile-Lipophile Balance) system is used for describing char-

acteristics of a surface-active agent. It consists of an arbitrary scale to which

HLB values are determined and assigned. If the HLB value is low, there is a

low number of hydrophilic groups on the surfactant and it is more lipophilic

(oil soluble). If the HLB value is high, there is a large number of hydrophilic

groups on the surfactant and it is more hydrophilic (water soluble) than oil

soluble. Some general applications of materials with various HLB values are

shown below:

1-3 Antifoaming agents

3-6 Emulsifying agents (w/o emulsions)

7-9 Wetting agents

27

8-18 Emulsifying agents (o/w emulsions)

13-16 Detergents

16-18 Solubilising agents

Surfactants with HLB values of 1-10 are oil soluble and 11-18, water soluble.

For example, to prepare an oil in water emulsion using stearic acid, an HLB

of 15 is required.

Information from MSDS Sheets

Some of the chemistries taken from MSDS sheets of currently used corrosion

inhibitors and demulsifiers are summarised below.

• Demulsifiers

Active components

1. Oxyalkylated amines

2. Alkyl benzene sulphonic acid

3. Polyoxyalkylene glycols

4. Alkylene oxide

Solvents

1. Light aromatic naphtha

2. 2-butoxyethanol

3. 2-ethyl hexanol

4. Aliphatic alcohols

28

5. Alkyl benzenes

6. Xylene

7. Aromatic solvent

8. Aromatic hydrocarbons

9. Aromatic hydrocarbons and alcohols

• Corrosion Inhibitors

Active components

1. Amine ethoxylate

2. Amine alkoxylate

3. Alkylamino propionic acid

4. Quaternary ammonium compounds

Solvents

1. Butanediol

2. Butoxyethanol

In addition, amides, imidazolines and phosphate esters are common corrosion

inhibitor ”actives”.

6 Chemistries Suggested

In terms of chemicals there was general agreement that corrosion inhibitors

and demulsifiers should be studied. One chemical company was more specific,

suggesting the project look at the following: quats, imidazolines and phos-

phate esters as corrosion inhibitors, and phosphonates as scale inhibitors.

29

They commented that most emulsion breaker and wax chemistry is poly-

meric (by implication, need not be investigated2), although some of the lower

molecular weight surfactant chemistry is of interest, e.g. alkoxylated alcohols

and amines.

One chemical supplier suggested the following generic demulsifier chem-

istry descriptors:

? Alkoxylated phenols and alcohols

? Alkoxylated alkyl phenol formaldehyde resin

? Alkoxylkated glycol

? Alkoylated amine

? Alkoxylated acids

? Alkoxylated sorbitol

7 Conclusions and Recommendations

I was hoping that the meetings and subsequent communications that I have

had with the sponsors would have enabled me to finalise the chemistries for

investigation. However, this has not been the case. There was a general

consensus that corrosion inhibitors and demulsifiers should be investigated,

but there was a lack of progress on generic classification. One company was

specific on chemistries for investigation. These are given in the previous Sec-

tion. In light of this I would suggest that these form the basis for discussion

2High molecular weight polymers will, theoretically, not pass through cell membranesand, therefore not bioaccumulate although they may be poorly degradable.

30

at the next steering group meeting, along with the existing CHARM default

surfactant chemistries.

31

Part II

EXPERIMENTAL

S. Gagliardi

32

1 Introduction

The present report summarises experiments and results obtained in the at-

tempt to quantify a series of oilfield chemicals in discharged produced waters

and compare the experimentally determined fractions released to the pre-

dicted CHARM values. The investigation has focused on corrosion inhibitors,

in particular on two types of surfactants:

? quaternary ammonium salts (QUATs)

? imidazolines

In the framework of this project, the instrument of choice is an electrospray

ionisation tandem mass spectrometer (ESI-MS/MS). This technique has the

sensitivity required for this type of analysis, i.e. down to 0.01 - 1 mg/l

depending on the substance. In addition the parent - daughter ion analysis

(MS/MS) is very specific and makes mistaken identification of compounds

very unlikely. In contrast, conventional wet chemical techniques do not have

the sensitivity or specificity to identify and measure specific oilfield chemical

substances in produced water.

In order to measure those compounds by ESI-MS/MS; three major prob-

lems need to be overcome:

1. the presence of salt in produced water which interferes with the mass

spectrometer measurements;

2. the matrix effects: produced water contains a whole range of organic

compounds, some of which may interfere with the analysis of the chem-

ical compounds of interest;

33

3. the adsorption of surfactants to the sampling containers, analytical

equipment and chromatography columns used in the analysis.

The use of deuterated internal standards should overcome these problems.

Deuterated standards have the same properties of their hydrogenous coun-

terparts, therefore the same behaviour but they are clearly distinguished by

the mass spectrometer since they have a different mass due to the substi-

tution of some of the hydrogen atoms with deuterium (see Figures 8 and

15). Further, as already pointed out, the use of tandem mass spectrometry

(MS/MS) avoids incorrect identification of peaks in the produced water (see

Figure 24) so that in no way hydrogenous and deuterated counterparts of the

same molecule can be mistaken for one another.

In this report (period May 2002 - October 2003) results are reported for:

• synthesis of imidazolines and quaternary ammonium salts, in their hy-

drogenous and deuterated forms;

• solid phase extraction (SPE) techniques applied to salty aqueous solu-

tions and produced water samples to remove the salt and extract the

oilfield chemicals to be analysed via mass spectroscopy;

• a new, fast on-line system that couples a high-pressure liquid chro-

matography (HPLC) column with the mass spectrometer;

• the use of the deuterated standards available, i.e. D-C12, D-C14, D-

C16 QUATs and D-(2:1) imidazoline, on produced water samples to

quantify the corresponding chemical residues.

34

N

N

NH2

PENDANT GROUP

HYDROCARBONTAI L

IM IDAZOLINEHEAD GROUP

Figure 1: Molecular structure of imidazolines.

2 Imidazoline Synthesis

Imidazolines are widely used in the oil industry as corrosion inhibitors, how-

ever their properties and behaviour in such complex environment is far from

being well known from a scientific point of view. For example, the mechanism

by which these compounds prevent corrosion is not entirely understood and

their obviously good performance has been only recently supported by ex-

perimental evidence [1–8] and investigated by molecular modeling techniques

[3, 6, 9–12]. This is because they are used in low concentrations and operate

in complex environment. For the very same reasons their quantification in

produced water is particularly difficult and only recently attempted [13–16].

In general, this class of compounds present a pendant group, an imi-

dazoline head group and a hydrocarbon tail, as shown in Figure 1. Recent

molecular modeling [3, 6, 9–12] studies suggest that the head and pendant

35

group promote bonding of the molecule to the surface, while the hydrocar-

bon tail forms a protective monolayer. This hydrophobic barrier protects the

surface from the water and corrosive ions, i.e. makes imidazolines effective

as corrosion inhibitor. However not every imidazoline is as effective: the hy-

drocarbon tail must be long enough (at least C8 [5]) to form the protective

film and cover the surface and the length of both the tail and the pendant

group must be such that the layer forms rapidly [9]. In addition, the pen-

dant group seems to play a role in locking the hydrocarbon tail into position,

reducing free motion of water to the surface [10]. In other words depending

on the specific molecular structure of the imidazoline, it may be more or less

effective as corrosion inhibitor.

Palmitic acid (CH3(CH2)14COOH) and diethylenetriamine (DETA)

(NH(CH2CH2NH2)2) were mixed under vacuum at 210 oC to obtain a mix-

ture of (2:1) and (1:1) palmitic imidazoline (see Figures 2 and 3). The

ratio between the two imidazolines synthesised varied depending on the molar

ratio between the reagents and the reaction time.

However, palmitic imidazolines were soon abandoned in favour of oleic

imidazolines, perhaps the most common class of corrosion inhibitors used

by the oil and gas industry. Oleic imidazolines are widely used because

of their good performances, which agrees with experimental observation that

these molecules absorb rapidly [9] and is the reason why they are often chosen

as a model molecule, including the present project.

Oleic acid (cis CH3(CH2)7CH=CH(CH2)7COOH) and DETA were mixed

under vacuum at 210 oC to obtain a mixture of (2:1) and (1:1) oleic imida-

zolines (see Figures 4 and 5). Note that both molecules carry a polar group,

36

N

N

(CH2)14CH3

NH2

Figure 2: Molecular structure of (1:1) palmitic imidazoline.

N

N

(CH2)14CH3

NH

O

(CH2)14CH3

Figure 3: Molecular structure of (2:1) palmitic imidazoline.

37

N

N

(CH2)7CH=CH(CH2)7CH3

NH2

Figure 4: Molecular structure of (1:1) oleic imidazoline.

i.e. an amine group NH2 for (1:1) oleic imidazolines and an amide group

NHCO for (2:1) oleic imidazolines, although the latter is followed by a rel-

atively long hydrocarbon chain that makes the molecule less water soluble

compared to (1:1) oleic imidazolines. This extra hydrocarbon chain not only

changes the nature of the molecule itself, but also the delicate equilibrium

between the pendant group and the tail that controls the effectivess of the

imidazolines as corrosion inhibitors. Different properties and behaviours are

therefore expected for these two imidazolines, along with a probable different

efficiency as inhibitors.

The reaction proceeds as shown in Figure 6. The reagents are mixed at

room temperature, however the salt formation may not be complete because

of the high viscosity of the mixture itself. The mixture is then transferred

to the heating apparatus, which is shown schematically in Figure 7. The

part of reagents that has not formed the salt is therefore heated up above

the boiling point of both oleic acid (Bp ≈ 195oC at 1.2 mm Hg) and DETA

(Bp ≈ 208oC). In theory they should cool down in the apparatus and reflux

38

N

N

(CH2)7CH=CH(CH2)7CH3

NH

(CH2)7CH=CH(CH2)7CH3O

Figure 5: Molecular structure of (2:1) oleic imidazoline.

back into the reaction flask. In practise because of the vacuum, some, in

particular DETA, are lost from the system. Even an initial molar ratio of

oleic acid to DETA of 1 : 5 does not lead to the exclusive formation of

(1:1) imidazoline as would be expected, but to a ratio of (1:1) : (2:1) oleic

imidazolines of 4 : 1 (see Table 6).

Unfortunately it turned out to be difficult to obtain a pure (1:1) oleic

imidazoline as reaction product when using very low amount of starting ma-

terials, which is the case with deuterated precursors, as explained in the

following paragraphs. Different reaction paths are possible and were briefly

investigated to improve the control over the synthesis products and minimise

the loss of reagents. However, the limited time available for this project did

not allow us further investigation of alternative imidazoline synthesis.

The deuterated imidazoline was synthesised using D2-9,10-oleic acid (Cam-

bridge Isotope Laboratories) instead of oleic acid (see Figure 8). In Figures

39

R

O

OH+ NH

NH2 NH2

OH2-

R

O

NHNH

NH2

R

O

NHNH

NH R

O

+

OH2-

N

N

R

NH2

N

N

R

NH

RO

+

R

O

O- NH

NH3+

NH2

Figure 6: Imidazoline synthesis reaction path.

40

H2O

H2O

T = 210 C

T ~ 20 C

vacuum

Figure 7: Apparatus used for imidazolines synthesis.

CH3

OHO

D

D

Figure 8: Molecular structure of D2-9,10-oleic acid.

41

Tab

le6:

olei

cim

idaz

olin

esy

nthe

sis

(tes

t13

refe

rsto

deut

erat

edim

idaz

olin

esy

nthe

sis)

.

TE

ST

Ole

icA

cid

DE

TA

Mol

arT

ime

MA

SS

SP

EC

INT

EN

SIT

IES

NR

(mol

)(m

ol)

Rat

io(h

rs)

AM

IDE

DIA

MID

E(1

:1)

IMID

AZO

LIN

E(2

:1)

IMID

AZO

LIN

ER

AT

IO(1

:1)/

(2:1

)

50.

010

0.05

01:

53

13<

510

025

4:1

150.

020

0.06

01:

33

4010

01:

2.5

80.

0003

50.

0003

31:

13

710

100

(2:1

)

90.

0003

60.

0003

51:

13

53

100

(2:1

)

100.

0003

70.

0003

51:

10.

5<

66

100

(2:1

)

110.

0003

50.

0007

2:1

0.5

510

0(2

:1)

120.

0003

80.

0003

51:

11

1410

0(2

:1)

140.

0003

50.

0035

1:10

0.5

10<

776

100

1:1.

3

110

<10

3010

01:

3.3

210

052

1:0.

5

130.

0003

50.

0003

81:

10.

53-

1010

0(2

:1)

42

0.0

0.1

0.2

300 310 320 330 340 350 360 370 380 390 400

m/z

Inte

nsit

y (n

orm

alis

ed to

1)

(1:1) IMIDAZOLINE

m = 350 AMIDE m = 368

Figure 9: Normalised mass spectra for synthesis 10 (red) and 13 (black) in therange m/z = 300 to 400.

9 and 10 synthesis 10 is compared to synthesis 13, i.e. the deuterated imi-

dazoline. The signal due to the amide is clearly absent in both cases while a

weak signal from the (1:1) imidazoline can be recognised only for synthesis

10 (Figure 9), i.e. the hydrogenous imidazoline synthesis. In Figure 9 the

hydrogenous and deuterated (2:1) imidazolines are clearly visible and distin-

guished from one another by the MS. A weak signal for a diamide ias also

present for synthesis 13.

The purity of the deuterated imidazoline has been assessed by comparing

it to an imidazoline provided by one of the chemical companies involved in

the project. From the chromatogram shown in Figure 11, the ratio between

the (2:1) and (1:1) imidazolines in the substance can be evaluated. Using

selected ion recording (SIR) analysis, and by comparing the peak areas of

the ions at m/z 348 and 612, 1ppm of the substance gives an area of 21.9

million ions (or 0.67ppm) for the (1:1) imidazoline and 10.8 million ions

(or 0.33ppm) for the (2:1) imidazoline. Assuming the relationship between

43

0.0

0.5

1.0

500 525 550 575 600 625 650 675 700

m/z

Inte

nsit

y (n

orm

alis

ed to

1)

(2:1) IMIDAZOLINE

m = 614.6 (2:1) d4 IMIDAZOLINE m = 618.7

DIAMIDE m = 634.6

Figure 10: Normalised mass spectra for synthesis 10 (red) and 13 (black) in therange m/z = 500 to 700.

concentration and signal intensity is linear, 1ppm of pure (2:1) imidazoline

should therefore give a peak area of approximately 32.6 million ions, which

is the area obtained from synthesised deuterated imidazoline. Figures 12

and 13 show the MS-MS spectra from oleic imidazoline, hydrogenous and

deuterated, respectively. The main daughter ion in Figure 12 corresponds to

the part of the molecule highlighted in red (m = 305). The corresponding

deuterated daughter is clearly visible in Figure 13 (m = 307), confirming the

product of the reaction is a deuterated imidazoline.

3 Quats Synthesis

Quaternary ammonium compounds, or QUATs, are cationic surfactants.

Although cationic surfactants account for only 5-6% of the total surfactant

production, they are extremely usefull for some specific uses, because of

their peculiar properties. They are not good detergents nor foaming agents,

44

2 3 4 5 6 7 8 9 10

time (min)

inte

nsit

y provided imidazoline_m=612.50

d4-imidazoline_m=618.70

provided imidazoline_m=348.50

area 32,536,394

area 10,751,146

area 21,936,192

Figure 11: Comparison of the peak areas in a SIR chromatogram between thedeuterated imidazoline and an imidazoline (substance) provided by one of thecompanies (1ppm solutions in MeOH:H2O=90:10).

dau of m = 612.5

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 100 200 300 400 500 600 700

m/z

Inte

nsit

y

306.1

NH

(CH2)7CH=CH(CH2)7CH3O

N

N

(CH2)7CH=CH(CH2)7CH3

Figure 12: MS-MS spectrum: daughter ions of m/z 612.50, (2:1) imidazoline.

45

dau of 618.70

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 100 200 300 400 500 600 700

Mass

Inte

nsit

y

308.9

NH

(CH2)7CH=CH(CH2)7CH3O

N

N

(CH2)7CD=CD(CH2)7CH3

Figure 13: MS-MS spectrum: daughter ions of m/z 618.70, d(2:1)imidazoline.

and they cannot be mixed in formulations which contain anionic surfactants,

with the exception of non quaternary nitrogenated compounds, or when a

catanionic complex synergetic action is sought. Nevertheless, they exhibit

two very important features:

1. their positive charge allows them to adsorb on negatively charged sub-

strates, as most solid surfaces are at neutral pH. The positive charge

enable them to operate as floatation collectors, hydrophobating agents,

corrosion inhibitors as well as solid particle dispersant

2. many cationic surfactants are bactericides. They are used to formulate

desinfectants for domestic and hospital use, and to sterilize food bottle

or containers.

Among cationic surfactants, QUATs are the dominant commercial ex-

ample. However, QUATs is a term used to describe a very wide range of

molecules. These molecules are in fact only associated through a quaternary

nitrogen in the structure as a common feature. Their use is as broad, span-

46

ning from detergents and biocidals to surfactants and pharmaceuticals. The

individual members of this broad family have very different properties. For

example monoalkyl QUATs are biocidal ingredients but have little surfac-

tant activity, on the other end twin chain (long) QUATs are mainly used as

surfactants and have no significant biocidal activity. The four arms of the

quaternary compound can look very different, and the molecules can be com-

pletely different functionally speaking. On the other hand, the counter-ion,

the negative chloride or methylsulphate ion included in the compound, seems

in most cases to make little difference to the properties of the compound. In

general, the positively charged nitrogen part of the molecule should attach

itself to surfaces (which for the most part are negatively charged) and there,

depending on the side chains, act as plasticiser, antistat agent, biocide, cor-

rosion protection in relation to a surrounding medium or otherwise change

the properties of the surface.

In the framework of this project, the interest is focussed on benzalkonium

QUATs or alkyl dimethyl benzyl-ammonium salts. Therefore in this report

the term QUATs refer to benzalkonium salts, where the alkyl side chain is a

long hydrocarbon chain, typically from C12 to C20 (see Figure 14).

As with the imidazolines, the QUATs synthesis was performed using non-

deuterated (cheaper) precursors, to evaluate the suitability and yield of the

different methods available. Once a suitable method had been established,

deuterated precursors were used. The synthesis is summarised in Figure 14.

Benzyl chloride (C6H5CH2Cl or C6D5CD2Cl) and the appropriate triamine

were mixed under vacuum at T ≈ 100oC for ≈ 1hr. The reaction was carried

out in MeOH:H2O, H2O or no solvent, best results being achieved in the

47

CH2Cl + N R

CH3

CH3

N+

CH3

CH3 R

Cl- R = (CH2)13 CH3

R = (CH2)15 CH3

R = (CH2)11 CH3

Figure 14: QUATs synthesis reaction path.

aqueous environment. The molecular structure of the deuterated ammonium

salts synthesised is shown in Figure 15. Figure 16 shows the mass spectrum

from the product obtained in Synthesis 1, i.e. C16 QUAT. The spectrum was

the same as that of a C16 QUAT standard bought from Aldrich. Further,

MS/MS showed the synthesised QUAT produced the same daughter ion spec-

trum as the Aldrich standard, confirming the synthesis had been successful.

The spectra are shown in Figures 17 and 18. The purity of the reaction

product can be checked with the MS, since any trace of triamine left would

be detected, as shown in Figure 19 for the synthesised C14 QUAT (Synthesis

3), where the product is clearly rich in unreacted triamine (m=242). The

spectrum shown in Figure 20 shows the same quaternary ammonium salt

purchased from Aldrich, no triamine can be detected in this case.

Deuterated QUATs were synthesised using fully deuterated benzyl chlo-

ride instead of its hydrogenous counterpart. Figure 21 shows the mass spec-

trum for D7 C16 QUAT, where traces of triamine and hydrogenous C16 QUAT

48

CD2 N+

CH3

CH3

R

DD

D

D D

Figure 15: Molecular structure of the deuterated quaternary ammonium saltssynthesised where R is either (CH2)11CH3 (C12 QUAT), (CH2)13CH3 (C14 QUAT)or (CH2)15CH3 (C16 QUAT).

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 100 200 300 400 500 600

Mass

Inte

nsit

y

QUAT m = 360

Figure 16: Mass spectrum from Synthesis 1 product (C16 QUAT).

49

0.0

0.5

1.0

0 50 100 150 200 250 300 350 400

m/z

Inte

nsit

y(n

orm

alis

ed to

1)

N+

CH3

CH3 C16H33

Figure 17: Daughter ions from C16 QUAT, m/z = 360 (synthesis 1). Note themain daughter ion corresponding to the part of the molecule highlighted in red(m/z = 91).

0.0

0.5

1.0

0 50 100 150 200 250 300 350 400

m/z

Inte

nsit

y(n

orm

alis

ed to

1)

Figure 18: Daughter ions from C16 Quat, m/z = 360 (Aldrich).

50

0.0

0.5

1.0

0 50 100 150 200 250 300 350 400 450 500

m/z

Inte

nsit

y TRIAMINE m = 242

QUAT m = 332

Figure 19: Mass spectra of Synthesis 3 product, C14 QUAT.

0.0

0.5

1.0

0 50 100 150 200 250 300 350 400 450 500

m/z

Inte

nsit

y

QUAT m = 332

Figure 20: Mass spectra of C14 QUAT, Aldrich.

51

0.0

0.5

1.0

100 150 200 250 300 350 400 450 500

m/z

Inte

nsit

y(n

orm

alis

ed to

1) d7-C16 QUAT

m = 367.4

C16 TRIAMINEm = 270.4 C16 QUAT

m = 360.4

Figure 21: Mass spectrum for deuterated C16 QUAT.

can be detected. Figure 22 shows the corresponding MS-MS spectrum for

m/z = 367.40. Note that the main daughter ion corresponds to the one

observed in Figure 17.

In Figure 23 a comparison between the deuterated C16 QUAT synthe-

sised (red arrow) and the hydrogenous one bought from Aldrich (black ar-

row) is presented. The MRM chromatograms clearly show that the Aldrich

compound contains traces of C18, C14 and C12 QUATs. Although they are

present in very small concentrations, they are above background level, as

shown by the comparison with the blank response (blue arrow), especially

the C18 QUAT. On the contrary, D-C16 QUAT signals show no traces of C18,

C14 or C12 above background level, C16 QUAT being only slightly above this

treshold. This is consistent with the H- NMR also carried out on this sample:

deuteration level was found to be 98%, in agreement with the purity assays

of the reagents.

Finally, Figure 24 shows the spectrum of an oilfield preparation spiked

52

0.0

0.5

1.0

0 50 100 150 200 250 300 350 400

m/z

Inte

nsit

y(n

orm

alis

ed to

1) CD2

DD

D

D D

N+

CH3

CH3 C16H33

Figure 22: Daughter ions from D7 C16 QUAT, m/z = 367.40. Note the maindaughter ion corresponding to the part of the molecule highlighted in red (m/z =98).

with deuterated QUATs. The signals from the deuterated standards are

clearly distinguishable from their hydrogenous counterparts, as expected.

4 Analytical Techniques

Different techniques were used to analyse produced water samples containing

QUATs and imidazolines: dichloromethane (DCM) extraction, solid phase

extraction (SPE) and high pressure liquid chromatography (HPLC), all fol-

lowed by ESI MS/MS quantitative analysis.

These different techniques have intrinsic advantages and disadvantages;

for example the DCM and SPE extraction, followed by MS analysis, are time

consuming compared to direct injection onto the HPLC-MS system. On

the other hand the amount of other organic compounds present in produced

water samples varies widely from platform to platform and cleaning steps

53

Figure 23: MRM chromatograms for various QUATs ions from a MeOH:H2O solu-tion (blue arrow), D-C16 QUAT synthesised (red arrow) and C16 QUAT purchasedfrom Aldrich (black arrow) in MeOH:H2O directly injected into the MS.

54

0

20

40

60

80

100

0 50 100 150 200 250 300 350 400

m/z

Rel

ativ

e in

ten

sity C12 QUAT; FW=304 C18 QUAT; FW=388

C16 QUAT; FW=360

d7 C16 QUAT; FW=367

d7 C14 QUAT; FW=339

C14 QUAT; FW=332

Figure 24: Spectrum of a chemical preparation (containing C12, C14, C16 andC18 QUATs) that was spiked with D7 C14 and D7 C16 QUAT.

prior to injection may be necessary. A summary of pros and cons related to

each technique is given in Table 7.

4.1 DCM extraction

DCM extraction was carried out on at least 50ml of produced water, which

was extracted with 2x10ml of DCM. The extract was dried under N2 and re-

dissolved in MeOH:HCOOH (25mM aqueous solution) (50:50). The solution

was then injected into the MS (10ul loop, carrier solvent MeOH:HCOOH

(25mM aqueous solution) (90:10), flow 0.1 ml/min) where selected masses

were detected (MRM mode, i.e. parent/daughter ion transitions).

DCM extracts organic compounds from the aqueous solution, including

the ones under investigation, however most of the other compounds that may

cause interference, i.e. signal suppression, with the MS analysis, are also

extracted. Therefore, depending on the actual concentrations of analytes to

55

Table 7: Summary of advantages and disadvantages of the different techniquestested on produced water (PW) samples.

PROs CONs

SPE

1. SPE removes salts and pos-sibly other interfering or-ganic compounds from thePW

2. Samples can be concen-trated or diluted

3. QUATs can be eluted withMeOH and therefore di-rectly injected into the MS

1. The procedure is time con-suming

2. Imidazolines can be elutedwith CHCl3, therefore theextract needs to be driedand redissolved in a moresuitable solvent for the MS

DCM

1. Samples can be concen-trated or diluted depend-ing on the levels of analytespresent

1. The procedure is time con-suming

2. Other organic compoundsare extracted which may in-terfere with the analysis

HPLC

1. PW samples are injected di-rectly into the HPLC-MSsystem, the analysis is veryfast

2. There may be separationthrough the column, effec-tively cleaning the samplefrom interference

1. PW samples need to be di-luted (50:50) with MeOH-HCOOH (25mM)

2. If there is no separationthrough the HPLC column,the signal may be weak dueto interference

56

0 1 2 3 4 5

time (min)

Inte

nsit

yC18 (m/z=388.5)

dC16 (m/z=367.4)

C16 (m/z=360.4)

dC14 (m/z=339.3)

C14 (m/z=332.4)

C12 (m/z=304.5)

area = 730,000

area = 267,000

area = 53,000

Figure 25: DCM extract chromatogram (sample L) using a direct injection intothe MS.

be investigated and eventual matrix effects, the extract can be diluted or

concentrated simply by changing the amount of MeOH:HCOOH used in the

attempt to optimise the MS response.

An example of the matrix effects on DCM extracts is shown in Figures 25

and 26: the same sample (sample L - DCM extract) is directly injected into

the MS, giving the chromatogram shown in Figure 25, or passed through

the HPLC system, Figure 26. The areas obtained from the D-standards

are much lower than expected in both cases but clearly increasing when the

sample goes through the HPLC column. The increase could be due to some of

the contaminants being flushed off during the washing procedure (see Section

4.3) and/or some separation between the contaminants and the analytes in

the column. The signals from the hydrogenous QUATs are also very low but

increasing with the aid of the HPLC column, although the areas are too low

to consider the output reliable.

57

0 2 4 6 8 10

time (min)

Inte

nsit

y

C18 (m/z=388.5)

dC16 (m/z=367.4)

C16 (m/z=360.4)

dC14 (m/z=339.3)

C14 (m/z=332.4)

C12 (m/z=304.5)

area = 1,814,000

area = 603,000area = 72,000

area = 48,000

Figure 26: DCM extract chromatogram (sample L) using the HPLC - MS onlinesystem.

Figure 27 shows another DCM extract (sample Z) where the only signal

clearly detected, is the one for C12 QUAT, followed by a weak signal for

C14 QUAT, indicating a greater amount of the former in the produced water

sample. The fact that the D-standards are not visible at all, although present

at approximately 0.5 ppm each, points to a very high suppression of the signal

due to interference. In this case the HPLC column did not have the cleaning

effect clearly observed for sample L.

4.2 SPE extraction

SPE columns are commonly used to clean-up complex samples and/or con-

centrate low levels of analytes, prior to analysis. A variety of different SPE

columns are available depending on the chemical nature of the analyte re-

quiring analysis, and a number of methods well established. Unfortunately

protocols are not available for the chemistries under investigation.

58

0 2 4 6 8 10

time (min)

Inte

nsit

y

C18 (m/z=388.5)

dC16 (m/z=367.4)

C16 (m/z=360.4)

dC14 (m/z=339.3)

C14 (m/z=332.4)

C12 (m/z=304.5)

area = 447,000

area = 27,000

Figure 27: DCM extract chromatogram (sample Z) using the HPLC - MS onlinesystem.

The solid phase extraction method adopted is known as reversed phase,

tipically used to extract hydrophobic or even polar organic analytes from

aqueous samples. Reversed phase extractions are in fact relatively non-

specific, therefore a wide range of organic compounds is typically retained.

Figure 28 schematically shows how it works:

• First of all the sorbent mass is conditioned, which means that it is

prepared for effective interaction with the analytes by solvation, i.e

unwrapping of the side chains (see for example Figure 29 to 31).

• Then the SPE is equilibrated, i.e. prepared for the specific sample

matrix with a similar solvent. These first two steps are not shown in

Figure 28.

• At this point the SPE is ready to be used and the loading step follows:

the hydrocarbon chains on both the analyte and sorbent are attracted

59

to one another by low energy Van der Waals dispersion forces; the

analytes, and likely some of the contaminants as well, are retained.

• In order to remove the impurities that are bound to the sorbent less

strongly than the analytes and to rinse residual, unretained sample

components that may remain from the sample loading step (for example

salt), this is followed by a washing step. In other words, this step should

wash the contaminants off the column.

• Finally, the elution step should selectively desorb and recover the ana-

lytes by disrupting the analyte - sorbent interactions so that the target

analyte is eluted and collected.

The recovery and purity of the target analytes can be optimised by adjusting

the composition of the solvents used during each of the steps, i.e. loading,

washing and elution. In reversed phase, a combination of MeOH, MeCN and

a strong acid (such as HCl) is often required to obtain quantitative recoveries

for polar analytes. However, it is desirable to choose an elution solvent

that is compatible with the final analytical method. In the case of mass

spectrometry, HCl suppresses the signal, even at very low concentrations,

therefore should be avoided. In conclusion, very often a compromise between

optimum recoveries and compatible solvents needs to be reached.

In a previous project (MIME, Grigson et al, 2000), benzalkonium quater-

nary ammonium salts were successfully measured in marine sediments using

SPE for sample preparation. However, the method was not entirely satisfac-

tory, as acidified methanol was required as a solvent, reducing the sensitivity

of the ESI-MS analysis. A synthesised (1:1) imidazoline could be eluted from

60

LOADING RETENTION

WASHING

ELUTIONANALYTES of INTERESTDISPLACED BY THEAPPROPRIATE SOLVENT

SALT and CONTAMINANTS WASHEDOFF BY THE DISTILLED WATER

WATER andCONTAMINANTS NOTRETAINED BY THE SPECOLUMN

Figure 28: Schematic representation of reversed phase extraction through SPEcartridge.

61

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

OH

OH

OH

CH3

CH3

CH3

CH3

OH

OH

CH3

CH3

CH3

Figure 29: Schematic representation of a silica particle’s surface carrying C18 hy-drocarbon chains (C18 SPE column).

the columns but a synthesised (2:1) imidazoline could not. It should be noted

that the synthesised imidazoline was a palmitic imidazoline with a terminal

hydroxyl in place of the amine in the pendant group (see Figures 2 and 3).

In this project different SPE columns were tested using solutions contain-

ing imidazolines or QUATs in either H2O, brine or produced water (known

not to contain the substances under investigation), prior to analysis of pro-

duced water samples from platforms selected for the project. The two types of

columns selected were C18 (Figure 29), C8 (Figure 30) and C18 end-capped

(Figure 31) silica based columns, that is silica particles with hydrocarbon

side chains of different length and different amount of silanol groups, along

with polystyrene (PS) based (Figure 32) polymer columns. The best results

were obtained on C18 and PS columns for QUATs and PS for imidazolines.

62

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

OH

OH

OH

C CH3

C CH3

CH3

CH3

C CH3

C CH3

C CH3

OH

OH

Figure 30: Schematic representation of a silica particle’s surface carrying C8 hy-drocarbon chains (C8 SPE column).

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

-Si

CH3

CH3

CH3

CH3

CH3

CH3

CH3

C O CH3

C O CH3

C O CH3

C O CH3

C O CH3

Figure 31: Schematic representation of a silica particle’s surface carrying C18 hy-drocarbon chains where hydroxyl are substituted with metoxy groups(C18 end-capped SPE column).

63

C

Figure 32: Polystyrene chain (PS SPE column).

Some of those results are reported below3:

spe C18 - 1ml (MIME project)

sample C16 QUAT (0.001 mg in MeOH:Brine)

conditioning MeOH, H2O

washing 10 ml H2O

elution 6 ml Acidified MeOH

recovery 100%

spe PS - 1ml (trial X31)

sample C16 QUAT (0.001 mg in MeOH:Brine)

conditioning MeOH, MeOH:H2O

washing* 10 ml H2O

elution 6 ml Acidified MeOH

recovery 66%

3washing* means that the column has been dried before being eluted; MeOH:H2O isMeOH:H2O=90:10; acidified MeOH is MeOH with HCl (2% vol); wsi is a water solubleimidazoline; pw is produced water known not to contain the compounds of interest.)

64

spe PS - 6ml (trial X54)

sample C16 QUAT (0.005 mg in Brine)

conditioning MeOH, MeOH:H2O, H2O

washing 5 ml H2O

elution 10 ml MeOH

recovery 100%

spe PS - 1ml (trial X55)

sample C16 QUAT (0.005 mg in Brine)

conditioning MeOH, MeOH:H2O, H2O

washing 1 ml H2O

elution 5 ml MeOH

recovery 100%

spe PS - 1ml (trial X12)

sample WSI (0.01 mg in MeOH:H2O) followed by 5 ml Brine

conditioning MeOH, MeOH:H2O

washing* 5 ml H2O

elution 5 ml CHCl3

recovery (2:1) WSI = 100% (1:1) WSI = 30%

65

spe PS - 1ml (trial X25)

sample WSI (0.01 mg in MeOH:H2O)

conditioning MeOH, MeOH:H2O

washing 5 ml H2O

elution 3 ml MeOH(ext 1) then 5 ml CHCl3 (ext 2)

recovery ext 1: (2:1) WSI = 82% ; (1:1) WSI = 0% ;

ext 2: (2:1) WSI = 18% ; (1:1) WSI = 6%

spe PS - 1ml (trial X26)

sample WSI (0.01 mg in MeOH:H2O) followed by 5ml Brine

conditioning MeOH, MeOH:H2O

washing 5 ml H2O

elution 3 ml MeOH(ext 1) then 5 ml CHCl3 (ext 2)

recovery ext 1: (2:1) WSI = 72% ; (1:1) WSI = 0% ;

ext 2: (2:1) WSI = 14% ; (1:1) WSI = 8%

spe C18E - 6ml (trial E21)

sample WSI (0.01 mg in MeOH:H2O) mixed to 5ml Brine

just before loading

66

conditioning MeOH, MeOH:H2O

washing* 20 ml H2O

elution 20 ml CHCl3

recovery (2:1) WSI = 12% ; (1:1) WSI = 65%

spe PS - 6ml (trial X30)

sample WSI (0.01 mg in MeOH:H2O) mixed to 5ml Brine

just before loading

conditioning MeOH, MeOH:H2O

washing 4 ml H2O

elution 10 ml MeOH:H2O(ext 1) then 10 ml CHCl3 (ext 2)

recovery ext 1: (2:1) WSI = 7% ; (1:1) WSI = 0% ;

ext 2: (2:1) WSI = 75% ; (1:1) WSI = 40%

spe PS - 1ml (trial X32)

sample WSI (0.01 mg in MeOH:H2O) mixed to 5ml pw

just before loading

conditioning MeOH, MeOH:H2O

washing 5 ml H2O

elution 5 ml MeOH

recovery (2:1) WSI = 65% ; (1:1) WSI = 7%

67

spe PS - 6ml (trial X34)

sample WSI (0.01 mg in MeOH:H2O) mixed to 5ml pw

just before loading

conditioning MeOH, MeOH:H2O

washing 10 ml H2O

elution 2.5 ml MeOH:H2O(ext 1) then 10 ml CHCl3 (ext 2)

recovery ext 1: (2:1) WSI = 11% ; (1:1) WSI = 0% ;

ext 2: (2:1) WSI = 83% ; (1:1) WSI = 33%

Overall the best results were obtained using polystyrene (PS) based poly-

mer columns (Strata X, Phenomenex), using MeOH to elute QUATs and

CHCl3 to displace imidazolines after washing off the salt with distilled H2O.

The extract was directly injected into the MS when in MeOH. The chloro-

form extract was dried under N2 and redissolved in MeOH:HCOOH (25mM

aqueous solution) (90:10).

Figures 33 and 34 show the chromatograms obtained from sample L and

Z extracts, respectively. In the examples shown, the methanol solutions were

directly injected into the MS. It should be noticed that the two produced wa-

ter samples were spiked with different amounts of D-standards and that they

were concentrated 3 and 2 times, respectively, during the SPE extraction.

In order to prove that the analytes of interest are indeed retained by the

SPE column, the produced water “waste” from sample Z was collected during

68

0 1 2 3 4 5

time (min)

Inte

nsity

C18 m/z=388.5

dC16 m/z=367.4

C16 m/z=360.4

dC14 m/z=339.3

C14 m/z=332.4

C12 m/z=304.5

area = 1,622,000

area = 777,000

area = 735,000

area = 289,000

area = 77,000

area = 62,000

Figure 33: Chromatogram obtained from sample L SPE extract (concentrated x3) via direct injection into the MS.

0 1 2 3 4 5

time (min)

Inte

nsity

C18 m/z=388.5

dC16 m/z=367.4

C16 m/z=360.4

dC14 m/z=339.3

C14 m/z=332.4

C12 m/z=304.5

area = 2,280,000

area = 998,000

area = 864,000

area = 572,000

area = 93,000

Figure 34: Chromatogram obtained from sample Z SPE extract (concentrated x2) via direct injection into the MS.

69

0 2 4 6 8 10 12

time (min)

Inte

nsit

y

0 2 4 6 8 10 12

enlarged 100 times

Figure 35: Chromatogram from the produced water sample Z eluted from the SPEcartridge during the loading process. The inset shows the same graph enlarged (yaxis) 100 times.

sample loading on the SPE cartridge. The collected waste was diluted with

MeOH(HCOOH 25mM) (50:50) before being injected into the MS.

Figure 35 shows that there is no signal from the QUATs or from the

standards, as expected (note that the scale for the y-axis is the same as in

Figure 34; only when the scale is enlarged 100 times the flat signals can be

seen on the chromatogram, as shown in the inset, confirming the absence of

peaks).

As for the DCM extracts, when the SPE extracts are passed through the

online HPLC system, a further cleaning and/or separation of the analytes

from the contaminants may take place giving greater areas. This is shown in

Figures 36 and 37 for sample L and Z, respectively.

70

0 1 2 3 4 5 6

time (min)

Inte

nsit

y

C18 m/z=388.5

dC16 m/z=367.4

C16 m/z=360.4

dC14 m/z=339.3

C14 m/z=332.4

C12 m/z=304.5

area = 2,889,000

area = 1,170,000

area = 914,000

area = 390,000

area = 199,000

area = 119,000

Figure 36: Chromatogram from sample L SPE extract via HPLC-MS analysis (seealso Figure 33).

0 50 100 150 200 250 300 350 400 450 500

time (min)

Inte

nsit

y

C18 m/z=388.5

dC16 m/z=367.4

C16 m/z=360.4

dC14 m/z=339.3

C14 m/z=332.4

C12 m/z=304.5

area = 4,890,000

area = 1,603,000

area = 1,602,000

area = 884,000

area = 137,000

Figure 37: Chromatogram from sample Z SPE extract via HPLC-MS analysis (seealso Figure 34).

71

A B

10µµµµlLOOP

MSP M

W

SA B

10µµµµlLOOP10µµµµlLOOP

MSMSP M

W

S

Figure 38: Schematic representation of the HPLC - MS configuration: A andB are the carrier solvent reservoirs, P and M the pre and main HPLC column,respectively, S is the switching valve that directs the flow either to waste (W) orto the MS.

4.3 HPLC-MS

For direct LC-MS/MS analysis, the HPLC cartridge was set up online to the

MS using a unique configuration developed for the project. Figure 38 shows

a schematic representation of the system. The switching valve S is turned to

waste (W) when the sample is injected in the 10 µl loop (flow 0.2 ml/min),

once it reaches the pre-column (P) the analytes and some other organic

compounds are retained while the salt is washed off with distilled water.

After 2 min from injection, the carrier solvent is changed to MeOH:HCOOH

(25mM aqueous solution) (90:10) and the valve S is set towards the MS. The

sample thus travels to the main column (M) and then to the MS cleaned of

salt and possibly other organics that may interfere with the MS detection of

QUATs and imidazolines.

As pointed out in the previous sections, the produced water samples ex-

tracted with DCM or cleaned up using SPE may be either injected directly

into the MS via a loop or through the online HPLC column.

72

0 1 2 3 4 5 6

time (min)

Inte

nsit

yC18 m/z=388.5

dC16 m/z=367.4

C16 m/z=360.4

dC14 m/z=339.3

C14 m/z=332.4

C12 m/z=304.5

area = 1,493,000

area = 878,000

area = 730,000

area = 620,000

area = 97,000

Figure 39: Chromatogram obtained from sample Z via the online HPLC-MS sys-tem.

The best results were obtained using a cyano column (Luna CN, Phe-

nomenex) for QUATs and a titanium oxide column for imidazolines (Titan-

sphere TiO, GL Sciences Inc., Japan - through Hichrom Ltd, UK), both

coupled with a cyano pre-column (Security Guard, Phenomenex).

An example of chromatogram obtained from produced water sample Z is

shown in Figure 39, others are presented in the following sections.

5 Produced Water Analysis

5.1 Calibration Curves

Prior to the analysis of the produced water samples, tests were carried

out on solutions containing known amount of actives in order to check the

extent of a possible linear relationship between peak area and concentration.

QUATs solutions were made up using benzalkonium QUATs purchased from

73

Aldrich in either brine, i.e. NaCl (35g/l) in distilled water, or produced

water from an offshore platform known not to contain any of the analytes

under investigation and believed to be relatively clean. For imidazolines

however, a suitable method was only recently developed via TiO HPLC

column, therefore the calibration curve is built on MeOH:H2O solutions,

directly injected in the MS. Also, as the commercial imidazolines provided

are always a mixture of (2:1), (1:1) imidazolines, amides and diamides, the

use of D(2:1) was preferred.

In order to take into account any fluctuation in the MS response and/or

any interference effects, the QUATs solutions were spiked with the deuterated

standards and the peak area was reported as relative intensity, i.e. the area

was divided by the area corresponding to a fixed amount of D-standard.

Unfortunately this was not possible at the time when the D(2:1) imidazoline

calibration curve was run, since D-QUATs were synthetised later during the

project.

Small fluctuations could be observed in the areas of the D-QUATs from

sample to sample but in general the response remained constant, as shown

in Figure 40. Note that the various volumetric flasks (numbered from 1 to

9, see x-axis in Figure 40) contain variable amount of hydrogenous QUATs

(from zero to ≈ 600 ppb) and ≈ 100 ppb of deuterated standards.

An example of the calibration curves obtained is shown in Figure 41: the

red and black lines correspond to the best linear fit for brine and produced

water solutions, respectively.

The solutions were passed through the HPLC column set up on-line to the

MS, including the washing step. The fact that the two lines almost coincide

74

0

1000000

2000000

3000000

4000000

5000000

6000000

0 1 2 3 4 5 6 7 8 9 10

Volumetr ic #

Are

a

d C16 Brine d C14 Brine

d C16 Produced Water d C14 Produced Water

dC14 104 ppbdC16 102 ppbH-Quats ~600 ppb

dC14 104 ppbdC16 102 ppbNo H-Quats

Figure 40: D-QUATs areas for volumetric flasks 1 to 9 containing different amountof QUATs and a fixed amount of d-QUATs.

C16 PW y = 0.0085x

R2 = 0.9939

C16 Briney = 0.0084x

R2 = 0.9872

0

1

2

3

4

5

6

0 100 200 300 400 500 600 700 800

Conc (ppb)

Are

a no

rmal

ised

to d

-std

C16 Brine

C16 Produced Water

Figure 41: C16 QUAT HPLC analysis from brine and produced water solutions.Peak areas are normalised to D-C16 QUAT area (102 ppb) and reported as afunction of concentration, see text for details.

75

0 200 400 600 800 1000 1200

Concentration (ppb)

Are

aMRM 618.7 > 308.9

Figure 42: Calibration curve for deuterated (2:1) imidazoline up to 1 ppm. Peakareas were measured for various solutions (from ≈ 7 ppb to ≈ 1 ppm) of D(2:1)imidazoline in MeOH:H2O= 90:10

indicates that either the produced water used is fairly clean from interfering

compounds or the HPLC column has cleaned up the sample, either through

the washing step or because of separation along the column. Nevertheless,

the relationship between area and concentration is linear up to 600 ppb.

No further measurements at higher concentrations were carried out simply

because the system would be overloaded with QUATs.

As for imidazolines, as already pointed out, the procedure was slightly dif-

ferent: D(2:1) imidazoline solutions were prepared up to≈ 1ppm in MeOH:H2O=

90:10 and directly injected in the MS. The resulting calibration curve is shown

in Figure 42, the relationship is believed to be linear up to around 500ppb.

Note that in both cases conventional ±5% error bars were added to the

experimental data. In order to take into account a possible change in the

slope of the normalised area - concentration linear relationship when using

76

other produced waters containing the chemicals of interest but with a possible

very different matrix, a direct comparison to the deuterated standards was

preferred to the use of the calibration curves for the calculations.

5.2 Preparations

Deuterated (D4) (2:1) oleic imidazoline and deuterated (D7) C12, C14 and

C16 quaternary ammonium salts (QUATs) are available for use as internal

standards.

The platforms, preparations and produced water (PW) samples will be

referred to as F, G, L, M, S, T, W and Z. The five ones (F, G, L, M and

Z) where QUATs are the main focus are described in Section 5.3, the other

three (S, T and W) where imidazolines are the component of interest are

outlined in Section 5.4. Note that preparations F and Z contains both QUATs

and imidazolines, however, when more than one component is relevant for

CHARM calculations, only the one with the highest fraction release default

value is used in the calculations. Therefore, QUATs were the focus of the

analysis of produced water samples F and Z.

The preparations used on the platforms were spiked with deuterated stan-

dards in order to relate the amount of substances detected in the produced

water sample to the dosing concentration of the preparation used on the same

platform. Note that to calculate C18 - QUAT in the preparations, the C18

peak was computed using D7 C16 QUAT, since its deuterated counterpart is

not available. For the same reason, (2:1) and (1:1) imidazolines, amides and

diamides were all compared to D4 - (2:1) oleic imidazoline. Table 8 shows the

77

percentage of QUATs and/or imidazolines contained in the relevant prepa-

rations, along with the amounts of the main contribution to each class of

actives.

As it will be shown in the following sections, sample F has been par-

ticularly difficult to analyse and the same problems seem to apply to the

preparation used, which is why is reported as the percentage corresponding

to the information obtained by the chemical supplier. Preparation F is rich

in C12 QUAT, ≈ 5% according to MS measurements, so that the signals

from the other QUATs seem to be influenced by it. Various solutions of

preparation F, from ≈ 5 to ≈ 50 ppm, were analysed in order to quantify

all the QUATs present, however, the results obtained were not consistent so

that the nominal concentration given by the chemical supplier is reported in

Table 8. It should also be noted that whenever we received the same prepa-

ration at different times, we found the ingredients to be present in slightly

different quantities, probably due to batch to batch variation, which is why

whenever possible we preferred to use the results of the MS analysis rather

than the composition supplied. However, that implies that the preparation

sample received comes from the same batch as the one used on the platform

when the PW samples were taken. Two examples are shown in Figure 43:

the vials contain two different preparations, supposedly the same for the two

vials next to each other but even their colour is clearly different.

78

Table 8: Composition of preparations from MS analysis, dosage rate and relevantnotes.

SAMPLE

PREPARATION

DOSAGE NOTESMASS - SPEC

QUATs IMIDAZOLINEs

F 6.5 % 8.1% 75 ppmpreparationcomposition givenby chemical supplier

G4.0 %

10 ppm →≈ 4.7 ppm

water stream dilutedwith PW beforesampling point

C12 = 2.8 % -

C14 = 1.2 %

L5.2 %

10 ppm

C18 compared toD − C16; PW storedin a tank for a fewdays

C18 = 3.5 % -

C16 = 1.5 %

M5.1 %

200 ppm →≈ 40 ppm

PW diluted withwater from anotherplatform; storagetank as for sample L

C12 = 3.4 % -

C14 = 1.5 %

S20.9 %

≈ 6.0 ppmpreparationcomposition givenby chemical supplier

- (2:1) IMIDAZ

DIAMIDES

T20.9 %

≈ 4.5 ppmpreparationcomposition givenby chemical supplier

- (2:1) IMIDAZ

DIAMIDES

W -

20.1 %

N.A.samples taken beforeand after cleaningprocess

(2:1) IMIDAZ = 12.7 %

(1:1) IMIDAZ = 6.0 %

DIAMIDES = 1.3 %

Z3.8 %

30 ppm PW is reinjectedC12 = 2.8 % IMIDAZ 1 - 5%

C14 = 0.9 % according to MSDS

79

Figure 43: Preparation samples: the two vials on the right contain preparation Fand the two on the left preparation J

5.3 Quats

Depending on the specific sample, i.e. on the specific platform in terms of

chemicals used, oil extracted etc., the so-called matrix effect can be totally

different. Consequently the response to the different techniques may vary

greatly from sample to sample.

sample F

Before spiking the PW samples, preliminary tests are usually run on the

PW in order to eventually add the right amount of deuterated standards to

the containers. In the case of sample F that stage was never reached for two

reason:

1. the two glass bottles broke when in the freezer; they were put into

beakers when defrosted, therefore giving extra surface for the corrosion

inhibitors to stick on

80

0

20000000

40000000

60000000

80000000

100000000

120000000

140000000

0 2 4 6 8 10 12 14 16

time (min)

Inte

nsit

y

C12 overloaded

C14 overloaded

PW diluted 1:2 + 205 ppb dC16 + 208 ppb dC14

Figure 44: MS/MS chromatogram for sample F produced water diluted 1:2 throughHPLC on-line system for salt removal.

2. the preliminary analysis was inconclusive, as it will be outlined below

As usual a first set of measurements are carried out on the PW diluted 1:2,

but, as you can see in Figure 44, the sample is clearly overloaded by both

C12 and C14. Only when the chromatogram is enlarged 140 times, then

the deuterated standards’ signals are visible, as shown in Figure 45. The

sample was then diluted 10 times, as shown in Figure 46: although C12 is

still clearly overloaded, the signal from C14 and D7C14 have increased rather

then decresead. That could either indicate an interference from the great

amount of C12 or from some other compounds present in the PW that are

obviously been diluted too. The sample was therefore diluted up to 1:1000,

other examples are shown in Figures 47 and 48 where the PW was diluted

1:25 and 1:370, respectively. Although in Figure 47 the peaks’ areas seem

to indicate that the sample is diluted enough, the signals do not decrease at

all, again areas increase (note that D7C12 area does not change much but it

corresponds to a lower amount of deuterated standard). Figure 49 reports

81

0 2 4 6 8 10 12 14 16

time (min)

Inte

nsit

y

dC16 area = 683,000

d C14 area = 730,000

PW diluted 1:2 + 205 ppb dC16 + 208 ppb dC14

C16 area = 730,000

Figure 45: MS/MS chromatogram for sample F produced water diluted 1:2 throughHPLC on-line system for salt removal, as shown in Figure 44 with y axis enlargedin order to see the deuterated standards signals.

0 2 4 6 8 10 12

time (min)

Inte

nsit

y

C12 overloaded

dC14 area = 1,746,000

C14 area = 2,146,000

PW diluted 1:10 + 208 ppb dC14

Figure 46: MS/MS chromatogram for sample F produced water diluted 1:10through HPLC on-line system for salt removal.

82

0 2 4 6 8 10 12

time (min)

Inte

nsit

y

C12 area = 1,686,000

dC16 area = 1,233,000

C14 area = 175,000

dC12 area = 2,825,000

PW diluted 1:25 + 103ppb dC16 + 312 ppb dC12

Figure 47: MS/MS chromatogram for sample F produced water diluted 1:25through HPLC on-line system for salt removal.

0 1 2 3 4 5 6 7 8 9

time (min)

Inte

nsit

y

C12 area = 1,903,000

C14 area = 730,000

dC12 area = 2,319,000PW diluted 1:370 + 260 ppb dC12

Figure 48: MS/MS chromatogram for sample F produced water diluted 1:370through HPLC on-line system for salt removal.

83

0

3000

6000

0.00 0.05 0.10

1 / DILUTION

C12

ppb 1 : 250 1 : 50 1 : 25

1 : 10

Figure 49: C12 calculated amount in ppb from solutions at variuos dilution asa function of 1/dilution. Note that the line through the data points is not aninterpolation but simply a guide to the eye.

the results from the various measurements at different dilution, as a funtion

of inverse dilution, which means that the C12 concentration increases along

the x-axis from left to right. Three regions can be distinguished:

1. the response seems to be linear for low C12 concentration, corresponding

to PW solutions diluted at least 1:360, as shown in details in Figure

50. Peak areas typical values in this region can be up to a few millions.

2. This is followed by a non linear region for PW samples diluted less than

1:250 where the MS is overloaded.

3. With the C12 concentration further increasing, for example the PW is

diluted only 1:10, the MS is flooded and the peak area value is over 34

millions!

The same kind of behaviour is found for C14 QUAT although on a smaller

scale: as shown in Figure 51 a dilution of at least 1 : 20 is necessary to obtain

84

0

250

500

0 0.001 0.002 0.003 0.004 0.005

1 / DILUTION

C12

ppb 1 : 360

1 : 300

1 : 250

Figure 50: C12 calculated amount in ppb from solutions at variuos dilution as afunction of 1/dilution. In this case only the linear region is shown.

reliable results (see also the C14 signals in the chromatograms from Figure

44 to 48). Since the amount of C12 seems to be so much compared to any

other QUATs, the amount of preparation can be calculated simply using C12

and the fact that C12 equals ≈ 5% of the preparation, according to the MS

measurement of preparation F. If only the measurements carried out on PW

diluted at least 1:360 can be considered reliable, then we obtain the results

reported in Table 9 for sample F analysed via HPLC. It is not surprising that

there is quite a big variation in the results, C12 QUAT quantity goes from 68

to 82 ppm. That is simply a consequence of such a high dilution that implies

multiplying for a high factor in the calculations.

sample G

Two samples of about 250 ml were received in glass containers. Sample

G duplicates were analysed using all the three techniques available. HPLC

analysis gave a very poor response, probably due to low levels of QUATs

85

0

200

400

600

800

0.00 0.05 0.10

1 / DILUTION

C14

ppb

1 : 1001 : 50

1 : 25

1 : 10

1 : 15

Figure 51: C14 calculated amount in ppb from solutions at variuos dilution as afunction of 1/dilution.

Table 9: HPLC analysis results from various trials on diluted PW samples fromSample F.

DILUTION D7C12 (ppb) C12 (ppb meas) C12 (ppm calc) PREP. F (ppm)

357 520 207 74 1473

370 260 213 79 1576

417 520 174 73 1447

454 520 167 76 1513

500 520 136 68 1357

500 250 163 82 1628

1000 250 78 68 1560

86

0 2 4 6 8 10 12

time (min)

Inte

nsit

y

dC14 area = 833,000

C12 area = 176,000

C14 area = 36,000

dC12 area = 747,000 PW diluted 1:1.25 + 104ppb dC14 + 104 ppb dC12

Figure 52: MS/MS chromatogram for sample G produced water diluted 1:1.25through HPLC on-line system for salt removal.

rather than interference. As shown in Figure 52, the deuterated internal

standards response was in fact not too low. Note that the produced water

sample was diluted 80:20 rather than 50:50 in an attempt to improve such low

signals from the hydrogenous QUATs. This early conclusion was supported

by the DCM extraction and SPE results: these techniques allowed us to

clean and concentrate the sample, leading to a more reliable answer. Figure

53 shows the same sample DCM extracted and concentrated 5 times, the

signal clearly improved compared to the HPLC chromatogram. The same

can be said for the SPE analysis, again concentrating the extract 5 times

(Figure 54, see also Table 10). A further “cleaning” of the signals may be

obtained coupling DCM or SPE extraction with HPLC, whenever separation

occurs through the HPLC column, i.e. a further cleaning of the analytes

from possible contaminants may take place via chromatography, improving

the signals as shown in Figure 55, when the SPE extract from sample G is

passed through the online HPLC system.

87

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

time (min)

Inte

nsit

y

dC14 area = 3,304,000

C12 area = 823,000

C14 area = 402,000

dC12 area = 3,024,000

DCM conc x 5+ 260 ppb dC14 + 260 ppb dC12

Figure 53: MS/MS chromatogram for sample G produced water DCM extract,concentrated 5 times, direct injection into the MS.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

time (min)

Inte

nsit

y

dC14 area = 3,425,000

C12 area = 752,000

C14 area = 308,000

dC12 area = 2,907,000SPE conc x 5

260 ppb dC14 260 ppb dC12

Figure 54: MS/MS chromatogram for sample G produced water SPE extract,concentrated 5 times, direct injection into the MS.

88

0 2 4 6 8 10 12 14

time (min)

Inte

nsit

ydC14 area = 4,403,000

C12 area = 1,228,000

C14 area = 381,000

dC12 area = 4,088,000SPE + HPLC

conc x 5260 ppb dC14 260 ppb dC12

Figure 55: MS/MS chromatogram for sample G produced water SPE extract,concentrated 5 times, injected through the HPLC on-line system into the MS.

sample L

Two produced water samples were received, one of the sample was exten-

sively used for preliminary analysis and various trials, while the other one

was kept frozen. These samples in fact were received at an early stage of

the project, when the different techniques were being throughly investigated,

therefore the numeric results reported on Table 10 are based on the second

sample, analysed once the preliminary trials were considered satisfactory.

Samples L gave poor response with both HPLC and DCM extraction. The

HPLC-MS response was so low that the same sample was injected into the

MS using a 50µl loop, that is simply increasing the amount of sample actu-

ally entering the MS. This was done because the signals from the deuterated

standards were greatly reduced, indicating interference effects. Increasing the

loop capacity, it was possible to check that hydrogenous QUATs were indeed

present. Figures 56 and 57 show the chromatograms obtained using a 10 and

50 µl loop, respectively. In Figure 25 the DCM extract chromatogram was

89

0 2 4 6 8 10 12 14 16time (min)

Inte

nsit

yC18 m/z=388.5

dC16 m/z=367.4

C16 m/z=360.4

dC14 m/z=339.3

C14 m/z=332.4

C12 m/z=304.5

area = 367,000

area = 166,000

area = 23,000

Figure 56: MS/MS chromatogram for sample L produced water diluted 1:2 withMeOHthrough HPLC on-line system.

shown; coupling the two techniques improved the response but not enough

to ensure a reliable outcome (Figure 26). Note that with the DCM technique

the sample was concentrated 5 times, however, the signals did not increase ac-

cordingly, indicating that this technique did not help cleaning this particular

sample from other organic compounds that are causing a lot of interference.

In conclusion, for sample L only solid phase extraction gave a good enough

chromatogram, as shown in Figure 33. Obviously then, this is the technique

of choice in this case, where “cleaning” of the sample seems necessary and

achieved using solid phase extraction. The results were confirmed by cou-

pling SPE and HPLC, when the signals improved but the overall answer

remained the same, indicating a further separation through the HPLC col-

umn between contaminants and analytes but also a very efficient cleaning

step for this sample via SPE.

90

0 1 2 3 4 5 6 7time (min)

Inte

nsit

yC18 m/z=388.5

dC16 m/z=367.4

C16 m/z=360.4

dC14 m/z=339.3

C14 m/z=332.4

C12 m/z=304.5

area = 11,388,000

area = 5,075,000

area = 136,000

area = 257,000

area = 418,000

area = 126,000

Figure 57: MS/MS chromatogram for sample L produced water diluted 1:2 withMeOHthrough HPLC on-line system.

sample M

Two duplicates were received in plastic bottles. In this case the HPLC

technique not only gave a good result, but the amount so calculated was

confirmed by SPE. Examples are shown in Figures 58 and 59. The washing

step in the on-line HPLC system and the solid phase extraction both managed

to properly “clean” the sample, or this particular produced water sample is

not particularly affected by contaminants. DCM extraction was not carried

out on these samples.

sample Z

Duplicates were received from platform Z in metal tins. As for sample L, the

first sample was throughly used to test the techniques while the numerical

results reported in Table 10 are based on the analysis of its duplicate. In this

case the HPLC technique gave good results, as shown in Figure 39. However,

the sample gave a poor response when analysed via DCM extraction, in

91

0 2 4 6 8 10 12 14

time (min)

Inte

nsit

y

C12 area = 3,158,000

dC14 area = 1,320,000

C14 area = 292,000

dC12 area = 3,309,000

PW diluted 1:2 + 104ppb dC14 + 312 ppb dC12

Figure 58: MS/MS chromatogram for sample M produced water diluted 1:2 withMeOH:HCOOHinjected through the HPLC into the MS.

0 0.5 1 1.5 2 2.5 3 3.5 4

time (min)

Inte

nsit

y

C12 area = 1,978,000

dC14 area = 570,000

C14 area = 216,000

dC12 area = 1,942,000

SPE conc x 2 + 104ppb dC14 + 520ppb dC12

Figure 59: MS/MS chromatogram for sample M produced water SPE extract,concentrated 2 times, direct injection into the MS.

92

particular, although the sample was concentrated 2.5 times, the deuterated

standards signals where not present, indicating a large interference effect

(see Figure 27). On the other hand, the SPE procedure confirmed the HPLC

results, effectively cleaning the sample from the contaminants, as shown in

Figures 34 and 37.

A summary of the results obtained for all the samples containing QUATs,

is reported in Table 10. Note that calculations are not reported in Table 10

for sample Z analysis by SPE coupled with HPLC, this is due to the fact that

the increase in the peak area of C12 is such that it could be outside the linear

relationship range. Also not reported is DCM coupled HPLC for sample L

simply because the chromatogram did not improve enough compared to DCM

extract analysis and the response was still too low.

5.4 Imidazolines

Compared to QUATs, many more trials were necessary before a suitable

analytical protocol could be established for imidazolines. In particular, SPE

recoveries can be very low, depending on the sample matrix and HPLC re-

tention times very long, up to 30-40 min for (1:1) imidazolines, depending on

the column chosen. Times were eventually shortened using a TiO column

(retention times ≈ 5 min for (1:1) imidazolines). This was coupled with the

cyano pre-column for the salt removal (note that the pre-column has no effect

on the retention times).

93

0

100000

200000

300000

400000

500000

0 2 4 6 8 10 12 14

time (min)

Inte

nsi

ty(1:1)IMIDAZ @ 346.6

(1:1)IMIDAZ @ 348.5

(1:1)IMIDAZ @ 350.6

area = 634,000

area = 297,000

area = 371,000

Figure 60: MS/MS chromatogram for sample W3 produced water, diluted 1:2,HPLC on-line analysis: (1:1) imidazolines.

sample W

13 samples (in glass bottles) were received from platform W, of which 8

have been analysed. The samples are referred to as W1, W2 and so on.

HPLC analysis gave good results for these samples, some of them were also

investigated via DCM and SPE extraction, however these techniques gave

poor results. As an example, sample W3 chromatograms are reported in

Figure 60 to 62. Although the corresponding preparation contains about

12.6% of (2:1) imidazolines, 1.3% of the corresponding diamides and 6.0%

of (1:1) imidazolines, all the samples analysed resulted to contain only (1:1)

imidazolines.

samples S and T

Since samples S and T come from different platforms but the same field and

the same preparation is used, they are described here togheter. They were

received as duplicates in plastic bottles. In this case the preparation con-

94

0

40000

80000

120000

0 2 4 6 8 10 12 14

time (min)

Inte

nsity

AMIDE @ 364.5

AMIDE @ 366.5

AMIDE @ 368.5

DIAMIDE @ 626.6

DIAMIDE @ 628.7

DIAMIDE @ 630.7

DIAMIDE @ 632.5

Figure 61: MS/MS chromatogram for sample W3 produced water, diluted 1:2,HPLC on-line analysis: amides and diamides.

0

500000

1000000

1500000

2000000

2500000

0 2 4 6 8 10 12 14 16 18

time (min)

Inte

nsit

y

D(2:1) IMIDAZOLINE (500ppb) @ 618.7

(2:1) IMIDAZOLINE @ 608.7

(2:1) IMIDAZOLINE @ 610.6

(2:1) IMIDAZOLINE @ 612.7

(2:1) IMIDAZOLINE @ 614.7

area = 501,000

Figure 62: MS/MS chromatogram for sample W3 produced water, diluted 1:2,HPLC on-line analysis: (2:1) imidazolines.

95

0

50000

100000

0 2 4 6 8 10

time (min)

Inte

nsity

DIAMIDE @ 630.6 DIAMIDE @ 628.7

DIAMIDE @ 626.7 DIAMIDE @ 624.8

Figure 63: MS/MS chromatogram for sample S produced water, diluted 1:2, HPLCon-line analysis: diamides.

tained (2:1) imidazolines and corresponding diamides but no (1:1) imidazo-

lines. However, samples S and T gave no signal for any of the amides/imida-

zolines present in the preparation, as shown in Figure 63 to 65. Note that

on these two samples DCM extraction did not work as well as for other sam-

ples, especially sample S did not separate properly. This may indicate the

presence of other chemicals that enhance water miscibility of hydrophobic

compounds (surfactants) including DCM itself. Also these samples gave an

unidentified white precipitate when mixed with MeOH.

Imidazolines behaviour over time

One of the two duplicates of samples S and T, along with six samples coming

from platform W, were spiked with D(2:1) imidazoline and their behaviour

was followed over time via HPLC analysis. To samples S and T were added

1ppm of D(2:1) imidazoline while samples W were spiked with 500ppb. Since

their behaviour turned out to be quite similar, samples S and T analysis will

96

0

1000000

2000000

3000000

4000000

5000000

0 2 4 6 8 10

time (min)

Inte

nsit

y

IMIDAZ @ 614.6

IMIDAZ @ 612.8

IMIDAZ @ 610.8

IMIDAZ @ 608.6

D(21) IMIDAZ @ 618.7

0

60000

120000

0 2 4 6 8 10

area = 1,580,000

Figure 64: MS/MS chromatogram for sample S produced water, diluted 1:2, HPLCon-line analysis: (2:1) imidazolines.

0

1000000

2000000

3000000

4000000

5000000

0 2 4 6 8 10

time (min)

Inte

nsit

y

IMIDAZ @ 614.6

IMIDAZ @ 612.8

IMIDAZ @ 610.8

IMIDAZ @ 608.6

D(21) IMIDAZ @ 618.7

0

60000

120000

0 2 4 6 8 10

area = 1,104,000

Figure 65: MS/MS chromatogram for sample T produced water, diluted 1:2, HPLCon-line analysis: (2:1) imidazolines.

97

be outlined first:

? the produced water was analysed via HPLC over a 7 days period, each

time a sample was taken out of the original container and diluted 1:2

with MeOH:HCOOH (25mM). As described in previous reports, this

dilution gives the best response from PW analysed via HPLC.

? diamides/imidazolines signals were always at background level, i.e. be-

low ≈ 20ppb/40ppb. At these low levels, the signal is very noisy and

its outcome is therefore affected by a large error. For example the

highest signal recorded (inset in Figure 66) corresponds to just 18ppb

of imidazoline!

? D(2:1) imidazoline signal is constant (see Figure 67 or compare Fig-

ure 64 to Figure 66). This indicates no adsorption and/or exchange

with hydrogenous amides/imidazolines on the container walls (plastic

in these cases). In fact after 11 days the (emptied) containers were

extracted with DCM releasing back only a small amount of deuterated

imidazoline (see for example sample S DCM bottle extraction result-

ing chromatogram in Figure 68 and Figure 64 for comparison). To

compute the D(2:1) signal, the peak area needs to be compared to an

external standard, which leaves us with two options: the area is com-

pared to the area of a known quantity of D(2:1) in MeOH:HCOOH

or to the response of the deuterated standard in the produced water.

Since the extract is redissolved in MeOH:HCOOH and should be rel-

atively “clean” compared to the produced water, the first method is

preferred. The calculations showed that in 11 days only 48ppb and

98

0

1000000

2000000

3000000

4000000

5000000

0 2 4 6 8 10

time (min)

Inte

nsi

tyIMIDAZ @ 614.6

IMIDAZ @ 612.8

IMIDAZ @ 610.8

IMIDAZ @ 608.6

D(21) IMIDAZ @ 618.7

0

60000

120000

0 2 4 6 8 10

area = 1,570,000

Figure 66: MS/MS chromatogram for sample S, HPLC on-line analysis: (2:1)imidazolines after 7 days from spiking, in the inset the highest response from (2:1)imidazoline at m/z = 614.6, see text for details.

58ppb of D(2:1) have deposited on the containers out of ≈ 1ppm.

Six different samples coming from platform W were analysed over time: sam-

ples W1, W2 and W3 behaved in a similar way, different though from samples

W4, W5 and W6, again similar to each others:

? all samples were followed over a period of at least 7 days after been

added the deuterated standard;

? although preparation W contains both (2:1) and (1:1) imidazolines,

only (1:1) imidazolines can be detected in all the produced water sam-

ples;

? in samples W1, W2 and W3 the deuterated standard signal quickly de-

creases (2-3 days) (Figure 69) indicating absorption to glassware rather

than exchange since the hydrogenous diamides and (2:1) imidazolines

signals do not increase and the (1:1) imidazolines signals remain con-

stant (Figure 70). Note that while the exchanging between hydrogenous

99

0.000

0.002

0.004

0.006

0.008

0.010

0 1 2 3 4 5 6 7 8

time (days)

area

per

ppb

S T

Figure 67: Normalised peak area for D(2:1) imidazoline in samples S and T as afunction of time over 7 days from spiking.

0

1000000

2000000

0 2 4 6 8 10

time (min)

Inte

nsit

y

IMIDAZ @ 614.6

IMIDAZ @ 612.8

IMIDAZ @ 610.8

IMIDAZ @ 608.6

D(21) IMIDAZ @ 618.7

DIAMIDE @ 630.6

DIAMIDE @ 628.7

DIAMIDE @ 626.7

DIAMIDE @ 624.8

area = 282,000

Figure 68: MS/MS chromatogram for sample S DCM bottle extraction, HPLCon-line analysis.

100

and deuterated counterparts of the same molecule is expected until

equilibrium is reahced, the same cannot be said about the exchange

between molecules such as (2:1) and (1:1) imidazolines. These are in

fact part of the same family but at the same time different molecules.

? for samples W4, W5 and W6 the behaviour over time is completely dif-

ferent: the peak area of D(2:1) imidazoline is constant, i.e. there is no

absorption and/or exchange (Figure 71). Note that for these three sam-

ples, each measurement was carried out on samples spiked with 205ppb

of D-C16 QUAT just before injection, in order to take into account MS

efficiency. This was done in view of the possible D(2:1) absorption, ob-

served in the first three samples, that makes the deuterated imidazoline

useless in taking the variable MS efficiency into account.

? If we take the very first results as the most reliable for samples W1, W2

and W3, i.e. before the internal standard started to adsorb, then the

preparation present in the samples goes from 6ppm of W4 to 12ppm of

W5.

? Note that SPE and DCM gave poor results in all cases, DCM extraction

on the bottles gave generally poor results, and (1:1) imidazoline seem

to stay in the water layer.

6 Results Summary

A summary of QUATs and imidazolines measurements using the various

techniques on all the samples is reported in Table 10, along with the cal-

101

0

500

1000

1500

2000

2500

3000

0 2 4 6 8 10 12 14 16

time (days)

norm

are

a

Figure 69: Normalised peak area for D(2:1) imidazoline in sample W1 as a functionof time over 12 days from spiking.

0

500000

1000000

1500000

2000000

2500000

0 2 4 6 8 10 12 14

time (days)

area

(11) @ 346 (11) @ 348(11) @ 350

Figure 70: Peak areas for (1:1) imidazolines in sample W2 as a function of timeover 12 days from spiking.

102

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 1 2 3 4 5 6 7 8

time (days)

nor

m a

rea

Figure 71: Normalised peak area for D(2:1) imidazoline in sample W6 as a functionof time over 7 days from spiking.

culated equivalent of preparations. Whenever possible, all duplicates were

analysed, this was not the case for samples S, T and Z. Apart from those, if

only a single result is reported, the duplicates simply gave the same answer.

Although the single QUATs or amides/imidazolines are quantified by

comparison to their deuterated counterparts (unless stated), the correspond-

ing amount of preparation is calculated from the sum of QUATs or amides/imidazolines

measured. This is compared to their overall percentage in the preparation,

as measured by MS analysis and reported in Table 8.

Finally, Table 11 reports the CHARM predicted concentration of the

preparations in produced water, C ′pw, calculated as follows:

C ′pw = Cpw + 0.1Cpw (1)

C ′pw is the theoretical fraction released Cpw plus a safety factor that equals

10% of its value. Cpw is calculated as follows:

103

Cpw =fr · Ci · Fi

Fpw

(2)

where fr is the fraction released, default value for QUATs is 1, for imidazoline

0.1; Ci is the concentration of surfactants in total fluid, i.e. the dosage

rate (ppm); Fi is the total fluid production (m3/d) and Fpw is the total

water production (m3/d). Measured quantities are reported both as ppm of

preparation (see also Table 10) and as percentage of the predicted CHARM

values.

104

Table 10: Results obtained with the various techniques on the PW samples con-taining QUATs or amides/imidazolines (column 3).

SAMPLE METHODACTIVES PREPAR.

NOTES(sum in ppb) (ppm)

G

HPLC - - poor response

SPE 17 - 18 0.4 - 0.5 } PW concentrated x 5SPE + HPLC 16 - 20 0.4 - 0.5

DCM 16 - 20 0.4 - 0.5 } PW concentrated x 5DCM + HPLC 17 - 21 0.4 - 0.5

LHPLC - - no signals

SPE 118 - 131 2.3 - 2.5 } PW concentrated x 3SPE + HPLC 118 2.3

DCM - - Poor response

M HPLC 602 - 642 12

SPE 557 - 560 11

SHPLC 97 (0.5) background levels

SPE - - PW conc x 5

DCM - - Poor separation

THPLC 72 (0.3) background levels

SPE - - PW conc x 2.5

DCM - -

WHPLC 1126 - 2512 6 - 12 very low signals

SPE - - } poor resultsDCM - -

Z HPLC 517 14

SPE 637 17 PW conc x 2

105

Table 11: Comparison between measured concentration and CHARM predictionsfor samples containing QUATs or imidazolines.

SAMPLE

Ci C ′pw Cm % CHARM

EFFECTIVE CHARMMEASURED

PREDICTED

DOSAGE PREDICTION VALUE

(ppm) (ppm) (ppm) 100 · Cm/Cpw

G 4.7 7 0.4 - 0.5 6 - 8 %

L 10 12 2.3 - 2.5 21 - 23 %

M 40 48 11 - 12 25 - 28 %

S 6 1.8 0.5 28 %

T 4.5 1.1 0.3 27 %

W ? ? 6 - 12 ? %

Z 30 47.9 14 - 17 32 - 39 %

106

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