Lecture 15 Oil, Grease, Surfactants, and Hydrocarbons

Genium Publishing Corporation 293

Lecture 15Oil, Grease, Surfactants, and Hydrocarbons

Lectures 4 and 5 discussed the analysis of individual organic compounds by gaschromatography and gas chromatography-mass spectrometry. Use of thesemethods requires a specific defined target analyte, such as 1,2-dichlorobenzene.The instrument is calibrated for the specific target analyte, and part of theanalysis is the determination that the target compound is present and not beingconfused with another closely related compound such as 2-chlorotoluene.

There are literally millions of possible organic compounds that canpotentially be present in wastewater, and it is impossible to even consider tryingto analyze the sample for every compound. At the same time, the mass of thesenon-target organic compounds can contribute substantially to the pollutionpotential of the effluent.

There are test methods available that can directly or indirectly estimate theorganic loading of an effluent. Biochemical oxygen demand (BOD) discussed inLecture 6, is an indirect measure of the organic material present, as is totalorganic carbon, TOC. BOD is oriented toward measuring how much of the organicmaterial is degradable, but it is effected by contributions from degradableinorganic substances. TOC is a more complete measure. However, it requires thatthe material be soluble in the water sample, due to the mechanics of the sampleintroduction. Organic substances that are not soluble in water are inefficientlymeasured by either TOC or BOD.

The insoluble organic materials are of concern. Aside from any specific toxiceffect due to ingestion of a particular component of the mixture, insoluble organicmaterial can present environmental problems. Most persons are familiar with thepictures of the results of oil spills on the fauna and flora in the immediate area,the oiled birds and dead sea otters, the coated rocks. Insoluble organic materialsin effluent create the same problems only on a smaller scale because of thesmaller quantities (mg/L to g/L). Even on this smaller scale they can causedeath, coating the gill surfaces of fish, amphibians, insects, and other creaturesliving in water, preventing the transport of oxygen from the water into the animaland interrupting respiration.

The total amount of insoluble organic material in an effluent can beanalyzed. A simple isolation of the insoluble organic material from the waterportion of the sample and then determination of the weight of the isolatedmaterial is a valid direct measurement. The exact details of the isolation processdepend on the composition of the organic material. In broad terms, insolubleorganic material is composed of oils and greases, surfactants, petroleumhydrocarbons, and a variety of miscellaneous substances from chemicalmanufacturing and other industrial processes.

The term oil is meant to indicate a water insoluble organic material that is aliquid at room temperature. The term grease means a water insoluble organic

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material that is a solid or semi-solid at room temperature. There are otherconnotations that many people associate with these terms, such as oils meaning alubrication fluid, while a grease is a lubrication solid. However, the lubricationqualifier more or less limits one’s thinking to a petroleum-based product. Whilepetroleum-based components can be a significant contributor to particular oil &grease problems, there are many effluents that exhibit oil & grease without anytrace of petroleum. Under this broad definition of oil & grease, many substancesfall into the category.

Within the food industry, oil & grease in the effluent is largely composed ofedible fats of plant and animal origin. The sub-category term “edible fats” coversa lot of ground, although the common link within the group is the presence of afatty acid. A fatty acid is characterized as a long-chain aliphatic hydrocarbonwith a carboxylate group on one end. Stearic acid, the common name foroctadecanoic acid, is a widely distributed fatty acid of 18 carbon atoms.

H3CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CO2H

Fatty acids of plant and animal origin contain an even number of carbonatoms, as the biosynthesis is an acetic acid-based process. The naturally-occurring fatty acids all have common names, presented in Table 15-1, frequentlyreflecting the original source of the material. Palmitic acid was derived frompalm trees. The term saturated indicates that there are no double bonds in thecarbon chain. Unsaturated means that there are double bonds in the carbon chain,and polyunsaturated indicates there are more than one.

Table 15-1. Some common names for fatty acids

Common nameof acid

IUPAC name Number of carbonsand unsaturation

n/a Butyric 4:0

Valeric Pentanoic 5:0

Caproic Hexanoic 6:0

Enanthic Heptanoic 7:0

Caprylic Octanoic 8:0

Pelargonic Nonanoic 9:0

Caproleic 9-Decenoic 10:1

Lauric Dodecanoic 12:0

Tridecylic Tridecanoic 13:0

Myristic Tetradecanoic 14:0

Pentadecylic Pentadecanoic 15:0

Palmitic Hexadecanoic 16:0

Palmitoleic cis-9-Hexadecenoic 16:1

Lecture 15. Oil, Grease, Surfactants, and Hydrocarbons


Table 15-1. Some common names for fatty acids, continued

Common nameof acid

IUPAC name Number of carbonsand unsaturation

Margaric Heptadecanoic 17:0

Stearic Octadecanoic 18:0

Oleic cis-9-Octadecenoic 18:1

Linoleic cis-9,12-Octadecadienoic 18:2

Eleosteric cis-9,11,13-Octadecatrienoic 18:3

Linolenic cis-9,12,15-Octadecatrienoic 18:3

Arachidic Eicosanoic 20:0

Gadoleic cis-9-Eicosenoic 20:1

Arachidonic cis-5,8,11,14-Eicosatetraenoic 20:4

Behenic Docosanoic 22:0

Erucic cis-13-Docosenoic 22:1

Lignoceric Tetracosanoic 24:0

Nervonic cis-15-Tetracosenoic 24:1

Cerotic Hexacosanoic 26:0

Montanic Octacosanoic 28:0

Besides the straight-chain aliphatic fatty acids that are presented in Table15–1, there are fatty acids that are branched-chain, the most frequent branchbeing a methyl group, CH3-. There are also fatty acids with other functionalgroups attached to the hydrocarbon chain. The most common of these is ricinoleicacid, 12-hydroxy-9-octadecenoic acid, which has an alcohol group attached at the12 position. Ricinoleic acid is the major fatty acid (90%) found in castor bean oil.

The saturated fatty acids above C12, lauric acid, are solids and are classed asgreases. The rest of the fatty acids, particularly those that contain double bonds,tend to be liquids at room temperature and are classed as oils.

A fatty acid is a weak acid. In the acid-form it is soluble in organic solvents,poorly soluble in the very non-polar organic solvents like hexane, but very solublein more polar organic solvents like methylene chloride, ether, or alcohols. Thefatty acid salts of the alkali metal cations and ammonia tend to be soluble inwater, but salts with other cations such as calcium or magnesium can be quiteinsoluble. Fatty acids can be transformed into amides and esters, by reactionrespectively with amines and alcohols. Examples of these compounds arepresented in Figure 15-1. The fatty acid amides and esters find considerable usein industry. The fatty acid methyl esters (FAME) are an important set ofcommercial derivatives used in many diverse applications. Cholesterol isfrequently encountered as the alcohol component of a fatty acid ester.

Fatty acids are structural components of the triglycerides. The backbone ofthe triglycerides is glycerine (glycerol), a three-carbon molecule with a hydroxy-



group attached to each carbon, HOCH2CH2(OH)CH2OH. Three fatty acidmolecules are attached to the glycerine by formation of an ester with each of thehydroxy-groups. The three fatty acids may be the same or they may be different.Trilauren, for example, is illustrated in Figure 15-1.

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CNH2

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2COCH3

Stearamide

Methyl stearate

O

O

O

Triglyceride

CH2-O-CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3

O

CH-O-CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3

O

CH2-O-CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3

Figure 15-1. Fatty acid derivative compounds

The glycerides are just one member of the family of complex fatty acid-containing molecules found in living systems. Another family member is thephospholipids, where up to three fatty acids are esterified to a phosphate,P(=O)(O-fatty acid)3. Collectively the family is known as the lipids, which arecomponents of fat. The lipids serve as structural components of membranes aswell as being storage forms for excess fatty acids.

It would take an entire book to catalog all the possible contributors to oil &grease. Phenols are one such group, and are briefly discussed in Lecture 16.Additionally, one other industrially significant group of compounds that contributeto oil & grease will be discussed here, and these are the diesters.

Diesters are formed from a molecule that contains two carboxylic acidgroups. The simplest organic molecule with two acidic groups is oxalic acid,HO2CCO2H. In other members of the family, the two acid functions can beseparated by either an aliphatic chain or an aromatic nucleus. Representativemembers of the family are presented in Table 15-2.

Maleic acid and succinic acid, along with the aromatic species phthalic acidand 2,3-naphthalene dicaboxylic acid, exist in the acid form as an internalanhydride, -(O=)C-O-C(=O)-, forming a very stable ring.



Table 15-2. Representative organic diacids

Name Structure

Oxalic HO2CCO2H

Malonic HO2CCH2CO2H

Succinic HO2CCH2CH2CO2H

Fumaric (trans double bond) HO2CHC=CHCO2H

Maleic (cis double bond) HO2CHC=CHCO2H

Glutaric HO2CCH2CH2CH2CO2H

Adipic HO2CCH2CH2CH2CH2CO2H

Pimelic HO2CCH2CH2CH2CH2CH2CO2H

Suberic HO2CCH2CH2CH2CH2CH2CH2CO2H

Azaleic HO2CCH2CH2CH2CH2CH2CH2CH2CO2H

Sebacic HO2CCH2CH2CH2CH2CH2CH2CH2CH2CO2H

Phthalic COOH

COOH

Isophthalic COOH

COOH

Terephthalic COOH

COOH

2,3-Naphthalene dicarboxylic COOH

COOH

If the diacid is reacted with two molecules of alcohol, it forms a diester. Thediesters of phthalic and adipic acids are especially useful as industrial solventsand as plasticizers in many products. As an example, polyvinyl chloride is a hard,opaque, somewhat brittle plastic that finds use in the manufacture of rigid pipe forindoor plumbing. However, if polyvinyl chloride polymer is mixed with 40% byweight bis(2-ethylhexyl)phthalate, the diester of phthalic acid and 2-ethylhexylalcohol, a very flexible, transparent material is formed. This material can beextruded in tubing that is commonly sold under the tradename Tygon® for use inlaboratories.



The number of combinations of the diacids with different alcohols to formdiesters, and with amines to form diamides is almost infinite. The diesters anddiamides are used in many proprietary mixtures from many different parts ofindustry and are found in effluents from these industries, where they contribute tothe oil & grease.

The ability of the diacids to bond to two different molecules is exploited inthe polymerization process where the substances are used as either co-polymersor as cross-linking agents. Nylon 66 is one of the oldest commercial polymers andis composed of adipic acid and 1,6-diaminohexane,H2NCH2CH2CH2CH2CH2CH2NH2. Each end of an adipic acid molecule forms anamide bond with one end of a diaminohexane, which is bonded to another adipicacid in an endless chain. Excess diacids from the polymerization process can findtheir way into effluent wastewater where they contribute to oil & grease.

Surfactants will frequently be contributors to the oil & grease results,although they are not normally considered to be in the group of substances thatfall under the oil & grease definition. Surfactants, in addition to interfering withoil & grease results, can present significant environmental pollution problems.These include interference with the gill-based respiration of fish and other aquaticlife forms, formation of unsightly scums and foams downstream from effluentpoints, and degradation into potentially hazardous compounds. Surfactants arelong organic molecules that have a water soluble (hydrophilic) head and a waterinsoluble (hydrophobic) tail. Mixtures of water and oil normally will separate intotwo layers. If there are insufficient amounts of oil in the sample to form a distinctlayer, the oil will exist as tiny droplets suspended in the water. The surfactantsfunction by bridging the gap between the water and oil. The charged head of thesurfactant will reside in the water layer, while the greasy tail of the molecule willbe dissolved in the oil. Using a surfactant allows formation of a stable emulsion ofwater in oil, or oil in water (Figure 15-2). The surfactant stabilized droplets aretermed micelles.

Figure 15-2. Surfactant stabilized micelles



In the absence of oily materials in the water, the non-polar surfactant tailsprefer to be in air. Soap bubbles will form, with the surface of the bubble being anoriented layer of surfactant molecules. In the absence of air and oily materials, abilayer can form that has the greasy tails of the surfactant molecules in themiddle and the outsides coated with the charged heads. In living organisms,biosurfactants are integral to the formation of membranes to compartmentalizethe various structures of cells.

The oldest manufactured surfactants are the fatty acid soaps. These areformed by boiling animal fat in water to separate the triglycerides as an oily layerfrom the solid portion of the fat, then the crude triglycerides and other lipids aremixed and heated with wood ashes and water. When wood is burned the sodiumand potassium are converted to sodium and potassium oxides, Na2O and K2O.Addition of water to the oxides forms sodium and potassium hydroxide, NaOH andKOH. These strong bases react with the triglyceride to form the sodium andpotassium salts of the constituent fatty acids and glycerine. The water is allowedto boil off the mixture, and the solid residue is lye soap. The carboxylate anion ofthe fatty acid forms the charged head of the surfactant, and the aliphatichydrocarbon chain is the tail.

Lye soap is a fairly efficient surfactant and has been used extensively inmany cultures for washing clothes and dirty bodies. One of the drawbacks to itsuse is the formation of insoluble scums with cations other than sodium andpotassium. The term hard water arises from the interaction of the lye soap withmineral-laden water to form especially insoluble calcium and magnesium salts ofthe fatty acids as a scum. The presence of these cations make it hard to generatesoap suds and obtain proper cleaning action.

More advanced surfactants are designed to avoid the scum-forming problemsof the fatty acid soaps. Surfactants with heads of sulfates or sulfonates, replacingthe carboxylic acid heads of the fatty acids, are soluble in the presence of mostcations. Surfactants with negatively charged heads are termed anionic surfactants(Figure 15-3). The hydrophobic part of the anionic surfactants tend to includearomatic portions instead of simply having an aliphatic chain as is present in thefatty acids. These style of surfactants are widely used as detergents and cleaningagents. Biodegradation of these surfactants gives rise to nonylphenol, currentlyregarded as a potent endocrine disruptor.

CH3CH2CH2CH2CH2CH2CH2CH2CH2 SO2NA

Figure 15-3. Typical anionic surfactant, nonyl benzene sulfonate

Surfactants with positively charged heads, based on quaternary ammonium,[RN(CH3)3]+ or phosphonium salts, [RP(CH3)3]+ , are called cationic surfactants(Figure 15-4). These materials are potent disinfectants in addition to havingdetergent properties. They are not as widely used in the United States as theanionic or nonionic surfactants, but are used in hospital and food serviceestablishments.



CH3CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2N(CH3)3+

Figure 15-4. Typical cationic surfactant, lauryl trimethylammonium salt

A third class of surfactant lacks a discretely charged head; instead, a watersoluble polyether fragment forms the hydrophilic portion of the molecule (Figure15-5). This type of surfactant is called a nonionic surfactant. The head is derivedfrom either polyoxyethylene (POE), the polymerization product of ethylene oxide,or polyoxypropylene (POP), the polymerization product of propylene oxide.Nonionic surfactants are named based on the hydrophopic tail, and the number ofrepeating POE or POP units. For example, the nonionic surfactant pictured inFigure 15-5 is formed from nonyl alcohol and five POE units. It is called POE (5)nonyl alcohol ether.

The nonionic surfactants do not function in the same manner as the cationicor anionic surfactants to form micelles. Instead they solubilize inorganic materialsin organic solvents through cation chelation.

CH3CH2CH2CH2CH2CH2CH2CH2CH2

O

CH

2 CH

2

CH2CH2

CH2CH2 CH2CH2

CH2CH2

O

OOO

OH

M

Figure 15-5. Typical nonionic surfactant, illustrating chelation of metal (M)cation; POE (5) nonyl alcohol ether

There are also mixed surfactants. One such example is produced when asulfate group is esterified to the alcohol end of an nonionic surfactant. The mixedanionic-nonionic surfactants have properties of both classes; able to forminterfacial films and chelate cations.

The surfactants, due to the hydrophobic tail, will tend to be extracted fromaqueous samples into non-polar solvents used during oil & grease isolations. Theythen contribute to false positive oil & grease results. There are specializedmeasurement techniques for the surfactants.

Petroleum-derived materials are technically part of oil & grease and in somecases the entire oil & grease determination is composed of only petroleumproducts. Petroleum products come from crude oil, one of the biodegradationendpoints of buried plant and animal organic matter. Although crude oil iscommonly believed to consist of strictly hydrocarbons, most crude oils containsmall amounts of sulfur, oxygen, and nitrogen incorporated into the molecules,



most frequently incorporated into polycyclic aromatic molecules such as thethiophenes, furans, and quinolines.

The major hydrocarbon types in crude oil are paraffins (aliphatic straight andbranched hydrocarbons), olefins (straight and branched chain unsaturatedhydrocarbons), naphthalenes (cyclic saturated hydrocarbons), and aromatics(mono- and polycyclic aromatic hydrocarbons). The first letter of these fourgroups, PONA, is used in the petroleum industry as an acronym for the analysesof hydrocarbons. A petroleum product is characterized by the percentagecomposition of each of the PONA groups and the boiling point range for theproduct. A listing of some of the common petroleum products that can beencountered in wastewater effluents is presented in Table 15-3.

Table 15-3. Common industrial hydrocarbon solvents and fuels

Solvent/fuel Standard Boiling pointrange °C

Petroleum ether ACS reagent 30-60

Petroleum benzin (naphtha) - 35-80

Lacquer thinner - 93-115

Hexanes ASTM D1836 63-71

VM&P1 naphtha (ligroin) ASTM D3735

Type I - regular 120-150

Type II - high flash 140-175

Type III - odorless 120-150

Mineral spirits ASTM D235

Type I - regular2 149-213

Type II - high flash point 177-213

Type III - odorless 149-213

Type IV - low dry point 149-185

Kerosine ASTM D3699 205-300

Kerosene non-standard 175-325

Aromatic naphtha ASTM D3734

Type I - aromatic 100 150-175

Type II - aromatic 150 180-215

Fuel oils ASTM D396

Grade 1 - light distillate 215-288

Grade 2 - heavy distillate up to 338

Grade 4 - residual/distillate mix -

Grade 5 - residual -

Grade 6 - residual (Bunker C) -

1 Varnish Makers’ and Painters’ naphtha2 Also called Stoddard solvent, Texsolve S, and Varsol 1.



Table 15-3. Common industrial hydrocarbon solvents and fuels, continued

Solvent/fuel Standard Boiling pointrange °C

Naval distillate fuel (military) MIL-F-16884H end point 385

Aviation gasolines ASTM D910 75-170

Diesel fuel oils3 ASTM D975

Low sulfur No. 1 up to 288

Low sulfur No. 2 282-338

Grade 1 - light distillate up to 288

Grade 2 - heavier distillate 282-338

Grade 4 - distillate/residual mix -

Diesel fuel oil (military) VV-800-D

DF-A - Arctic grade up to 300

DF-1 up to 330

DF-2 up to 370

Aviation turbine fuels ASTM D1655

Jet A 205-300

Jet A-1 - low freezing point 205-300

Jet B - wide distillation range kerosine <145 to >245

Aviation turbine fuels (military) MIL-T-5624P

JP-4 145-270

JP-5 205-300

JP-5/JP-8ST (worst case test mixture) 205-300

JP-8 MIL-T-83133D 205-300

High-boiling hydrocarbon solvent for woodpreservative carrier

ASTM 2604 up to 307

Low-boiling hydrocarbon solvent for woodpreservative carrier

ASTM 3225 up to 213

Gas turbine fuel oils ASTM 2880

Grade 0-GT - mixture of Jet B + naphtha -

Grade 1-GT - distillate up to 288

Grade 2-GT - distillate up to 338

Grade 3-GT - distillate/residual mix -

Grade 4-GT - residuals + topped crude -

3 Grades 1, 2 and 4 are required to contain a visible amount of blue dye, 1,4-

dialkylamino-anthraquinone.



Determination of Oil & Grease

The determination of oil & grease has been sarcastically described as “thecutting edge of modern science.” It consists of extraction of a portion of thesample with an organic solvent, then evaporation of the solvent from a tared flask.The residue in the flask is weighed. The oil & grease result is the amount ofresidue in mg divided by the sample amount, expressed as either mg/L or mg/kg,depending on whether the sample is liquid or solid.

Although the technique is very simple in concept, great variations in resultsoccur because of differences in the details of how the simple concept isimplemented. The determination is quite amenable to a full slate of qualitycontrol measures such as blanks, laboratory controls, matrix spikes, performanceevaluation samples, etc.. As with the determination, the utility of the qualitycontrol results lies in the details of how they are formatted and performed.

The first concern in oil & grease determination is the collection of thesample. Oils and greases, by definition, are not soluble in water. The effluent hasthe oil and grease present in the form of microdroplets or tiny suspended particlesif the concentrations are low. Higher levels of the analytes in the samplecommonly appear as an actual layer on top of the water. The term “free product”is often used to describe this condition, especially when petroleum hydrocarbonsare present. The layer can range from floating semi-solid chunks of grease to agasoline-like sheen on the surface. Although we most commonly associate oilsand greases with materials floating on the top of the water column, this is notalways the case. There are oils and greases that are heavier than water and willsettle to the bottom of the container. Dense oils and greases are frequentlycomposed of halogenated solvents and other materials. Examples of these arechloroform, perchloroethene, and the polychlorinated biphenyls.

Key to obtaining a representative sample for oil & grease determination is tocollect the sample from an area of vigorous mixing. When the water is quiescent,the analytes segregate from the bulk of the water. If the oils and greases arelighter than water, the sample can vastly over-represent the total concentrationdue to a skimming action from the surface. Dense oils & greases will be vastlyunder-represented as they layer the bottom of the water body.

The mechanics of the sampling affect the results. Oil and grease are notstable in water as a homogeneous mixture. Presented with a surface, they willstick to it rather than remain suspended in the water. The walls of the containerwill most commonly be coated with the majority of the oil and grease originallyin the sample. For this reason containers used for collection and shipment of oil &grease samples must never be pre-rinsed with the sample. The first rinse coats thewalls of the container with oil and grease, then the water is dumped out andanother coat of oil and grease applied to the walls with the next rinse, resulting ina concentration effect. Composite samplers must never be used for collecting oiland grease samples, because the majority of the analytes end up coating thetubing inside the sampler rather than being delivered to the collection bottles.Plastic containers must never be used for sample collection because oils andgreases can dissolve into the walls of the container and be lost from the analysis.The proper technique is to collect a sample from a well-mixed area as a singlegrab using a wide-mouth glass container.



Preservation of the sample is performed by adding sulfuric acid until the pHis less than 2 and then cooling the sample to 4 °C. The acidification serves to haltbiological activity in the sample. Most microorganisms can degrade oil andgrease components, and their activity can reduce the amounts present, even whenthe sample is cooled to 4 °C. The addition of acid can also convert fatty acidsfrom water soluble salts to non-water-soluble free acids, increasing the oil andgrease content. The pH of the sample after acid preservation should never bechecked by dipping a pH probe or pH paper into the sample itself, or by pouringoff an aliquot for checking. These actions serve to reduce the sample oil andgrease content. Surface oils and greases will adhere to the paper or probe, orpreferentially decant with the aliquot. A separate container of sample should beobtained so that the amount of acid necessary to lower the pH below 2 isdetermined on it, then the contents of this preservation test container arediscarded. The same amount of acid is then added to the other oil & greasesample containers.

Each container of sample is a single sample. This means that multiplecontainers of the sample must be taken to perform duplicates and other qualitycontrols. The reasons behind this requirement are the same as those givenpreviously for sample collecting. The oils and greases are attached to the walls ofthe container, and no amount of shaking will ever evenly disperse them back intothe water. This means that dividing the sample into identical sub-samples is notpossible. This concern also applies to using a bucket or other secondary containerto collect a sample from a conduit or manhole, then pouring sub-samples from thebucket into glass sample containers. Low oil and grease values will be obtainedas most of the analytes are attached to the sides of the bucket and do not gettransferred to the jar.

The isolation of the oil and grease from the sample is achieved by extractionwith an organic solvent in a separatory funnel. A separatory funnel is a pear-shaped flask with a tight-fitting stopper at the top of the flask and a stopcock atthe bottom. The stopper and stopcock plug should be constructed of a fluorocarbonpolymer such as Teflon®. Fluorocarbon polymers are organic materials; however,oils and greases will not dissolve into the body of the polymer and are easilywashed from the surface with organic solvents. Avoid glass stopcock plugsbecause the lubricant that must be used with them will dissolve in the organicsolvent and contribute a false positive interference to the oil and greasedetermination.

Complete recovery of the oil and grease from the sample container is notachieved by simply pouring the sample out of the sample bottle into theseparatory funnel. Complete recovery requires rinsing the empty container with atleast one portion of the solvent that is being used for the oil & grease isolation. Ifa plastic container has been used for the sample, plasticizers and other materialsthat are in the plastic are extracted by the solvent, which then contribute to falsepositive interferences in the analysis. And, it is not sufficient to add several mL ofthe extraction solvent to the container, swirl it around and then add it to theseparatory funnel. Oil and grease can adhere to the lid of the container and mustbe recovered. A portion of the extraction solvent has to be added to the container,the lid replaced on the container and then the container vigorously shaken for a



minute or so. Performing this action with two portions of the extraction solventrecovers all the oil and grease.

A number of different organic solvents have been used for the extraction.Back in the early 1970s, hexane (a mixture of C6 saturated hydrocarbons,containing mostly n-hexane with lesser amounts of methylpentane, cyclohexane,and methylcyclopentane, and most appropriately called hexanes) was commonlyused. During the latter part of the 1970s Freon 113 (1,1,2-trifluoro-2,2,1-trichloroethane) was introduced.

Compared to hexane, Freon 113 has some distinct advantages. It is notflammable, while hexanes are very flammable, being on a par with gasoline.Freon 113 is heavier than water, while hexanes float on the water. Using hexanein a separatory funnel extraction requires the analyst to drain the water sampleout of the funnel after each extraction, pour the hexane out of the separatoryfunnel into a flask, then pour the water sample back into the separatory funnel,add more solvent and shake the separatory funnel again. Freon 113 sinks to thebottom of the separatory funnel. After each extraction all the analyst has to do isallow the layers to separate, then drain the solvent out through the stopcock. Nextthe analyst adds more solvent through the top of the funnel and can begin shakingthe funnel.

Emulsions that form during the solvent extraction have different characterwhen a heavier-than-water solvent is used as compared to a lighter-than-watersolvent. The lighter solvent forms an emulsion that contains air froth, whichmakes the emulsion more difficult to break by stirring. Emulsions with Freon 113contain no air and can frequently be dispersed by gently stirring with a glass orfluorocarbon polymer rod. Simply filtering the emulsion through a glass-fiber filteris also effective.

Freon 113 is somewhat more polar than hexanes and is a better solvent forthe fatty acid-based components of oil and grease. Hexanes tend to be a bettersolvent for the petroleum hydrocarbon chemicals.

Hexanes boil at 68-70 °C (pure hexane boils at 68 °C) while Freon 113 has aboiling point of 48 °C. During the solvent removal step of the oil and greasedetermination, the hexane extract must be heated to a higher temperature thanthe Freon 113 extract. This results in greater loss of the more volatile oil andgrease components. The high flammability of the hexanes requires that spark- andexplosion-proof heating devices be used.

Overall, the replacement of hexanes with Freon 113 was a dramaticimprovement for the laboratory from the standpoint of health, safety, and ease ofanalysis. Freon 113 is essentially non-toxic to humans; however, it is one of thesubstances identified as an ozone-depleting chemical. Its manufacture and usehas been banned by the Clean Air Act and in countries that are signatories to theMontreal Protocol on Substances that Deplete the Ozone Layer. Since 1992,added federal taxes on the sale of Freon 113 have increased the price of thesolvent over 50-fold. Availability of Freon 113 has plummeted, and there hasbeen an accompanying precipitous drop in the purity and quality of the solventeven when it can be purchased.

The approved oil and grease methods that use Freon 113 (EPA Method 413.1and SM18 5520 B) have suggested a number of different materials for use inspiking solutions. These range from Wesson® oil (corn oil), to heavy mineral oil



and number 2 fuel oil. The EPA has prepared the WP check samples from amixture of cooking oil and paraffin oil. All of these substances have the commoncharacteristic that losses are almost non-existent through volatilization due tooverheating the extract during the solvent removal step. Corn oil is composed of96% triglycerides of mostly palmitic, stearic, oleic and linoleic acids, with up to2% phospholipids of vegetable lecithin (phosphate ester of choline,HOCH2CH2N+(CH3)3 esterified to a diglyceride) and inositol(hexahydroxycyclohexane) esters, and up to 2% miscellaneous fatty alcohols.Mineral oil, also called paraffin oil and liquid petrolatum, is a complex mixtureof long-chain hydrocarbons, essentially non-volatile.

The EPA has distributed a proposed replacement method, EPA Method 1664,N-Hexane Extractable Material (HEM) and Silica Gel Treated N-HexaneExtractable Material (SGT-HEM) by Extraction and Gravimetry (Oil and Greaseand Total Petroleum Hydrocarbons), for oil and grease determinations. Afterexamining numerous solvents and solvent mixtures, the decision was made toreturn to the extraction solvent used during the early 1970s, hexanes. There areother significant differences in Method 1664.

The spiking solution components are hexadecane and stearic acid. These twosubstances are unlike any of the previously used components of spiking solutions.Stearic acid is a very polar material, only soluble to a small extent in hexane.Further, it sticks to glass surfaces, and significant portions can be lost during thetransfer of hexane solutions or aqueous solutions from pipettes to separatoryfunnels to flasks. Pre-treating the glassware with a silanizing agent such asdichlorodimethyl silane or bis(trimethylsilyl)acetamide can effectively de-activate the glassware. A less effective but easier approach is to acid rinse all theglassware with 5% sulfuric acid immediately before use. Hexadecane is readilysoluble in hexanes, but it is a very volatile material. Over enthusiastic heating ofthe sample during the solvent evaporation step can result in complete loss of thiscomponent. Although the method directions call for a single spike solutioncontaining both spike components, more consistent results are obtained whenseparate hexadecane and stearic acid solutions are prepared and used.

Weighing the residue on the analytical balance is the determinative step inMethod 1664. The balance calibration is checked, with standards, immediatelybefore and after the residue weighings. The two standards are a 2.00 mg and a1000 mg calibration weight of at least ASTM Class 24 quality (equivalent to theold NBS/NIST Class S or S-1 weights). The manufacturer’s tolerances of theweights are 2.00 ± 0.014 mg and 1000 ± 0.054 mg. The balance should read within± 0.05 mg and ± 2.0 mg, respectively, for these checks.5 Maintaining the checkweights within tolerance means keeping them in a controlled humidity area(desiccator) and never touching them with anything other than the nylon tweezersthat are supplied with the weights. The analyst should have the weights checkedeach year during the annual balance service. Although the service person cannotre-certify the weights, he can see if they are within tolerance as compared to hisClass 1 weights that are used to calibrate the balance. The weight manufacturer

4 ASTM Standard E 617.5 NIST Handbook 44.



can re-certify the weights, as can the state Weights and Measures laboratory(often under the state Department of Agriculture).

Method 1664 has a defined batch and quality control protocol. An InitialPrecision and Recovery (IPR) study is performed along with a Method DetectionLimit (MDL) study. These are separate quality control procedures, using differentconcentrations of stearic acid and hexadecane. The Minimum Level (5 mg/L) isused for reporting sample results and is calculated based on the MDL results. Abatch consists of up to 10 analytical samples with a blank, Ongoing Precision andRecovery (OPR, equivalent to a laboratory control sample), matrix spike andmatrix spike duplicate, for a total of 14 analyses.

The recovery and RPD objectives for the OPR and the MS/MSD arespecified in the method as 79-114 %R and 0-18 RPD. These are very tight limitsfor this procedure and can be obtained only with very close attention to detail.Both high and low recoveries can be problems.

A high OPR recovery generally indicates incomplete removal of the solvent.The method suggests use of a distillation flask, head, and condenser for removalof the solvent, using a hot water bath as the heat source. This is a very slowprocess when hexane is the solvent and frequently leads to incomplete solventremoval. The last traces of solvent can be removed by blowing out the flask witha moderate gas stream from a cylinder. This works well if the flask is still warm;however, purified laboratory grade nitrogen or compressed air should be used. Airfrom an air compressor or a cheap grade of gas can be contaminated with oil orwater and contribute weight to the sample. Other techniques for solvent removalinclude use of a vacuum-assisted rotary evaporator or simply placing the flask ona hot plate. The water bath should be set to a temperature only slightly aboveroom temperature, not heated to boiling. The controlled conditions of the rotaryevaporator allow very fast removal of the solvent and can lead to consistentlygood OPR recoveries. The hot plate is largely uncontrolled and whileevaporations are fast, tend to give low recoveries unless constantly watched.

Low OPR recoveries suggest either overheating of the sample or loss ofstearic acid through adsorption to the glass. Differentiation of the two causes ispossible by using the two OPR components separately; however, the cause shouldbe traced and eliminated.

The MS/MSD results will be affected by the sample spike. If samplescontaining large amounts of oil & grease are consistently encountered, the spikelevel should be increased to at least the background amounts in the sample. Theanalyst should also be flexible in matching the spike to the composition of the oil& grease in the sample. Some samples consistently give low recoveries of stearicacid due to a significant presence of petroleum hydrocarbon. For these samples,stearic acid is not particularly informative, and a matrix spike of only hexadecanegives more useful information.

Some grades of hexane have been observed to produce a residue. New lots ofextraction solvent should be checked by concentrating about 100 mL anddetermining the residue. Preliminary distillation of the hexane prior to its use inextractions can remove any non-volatile residues.

EPA Method 1664 is in compliance with the EPA Performance BasedMeasurement System (PBMS, discussed further in Lecture 22). Aside from theseparatory funnel extraction, there have been several alternate oil & grease



isolations that have been found to be more or less acceptable in particularsituations and might be acceptable as PBMS modifications. One facility filtersthe oil & grease sample through a wet cellulose paper filter, then extracts thefilter in a Soxhlet extractor using hexane (similar to the old oil & grease methodfor sludges in the 12th Edition of Standard Methods, and currently listed as SM5520 D). Several manufacturers of solid phase extraction columns and disks havebeen promoting these devices as a quick and easy means to oil & greaseisolation. The sample is sucked through the disk or column with vacuumassistance, then the oil & grease is eluted with an appropriate organic solvent andthe residue determined. A lighter-than-water continuous liquid-liquid extractor foruse with hexane has been found to generate excellent recoveries; however, theinitial capital costs for the glassware and 18-hour extractions are drawbacks.



Oil & Grease Data Review Checklist

YES NO Review Item

Analytical balance checked twice each day with 2 and 1000mg standard

No subsamples taken from sample container

Demonstration of ability to achieve required MDL

All field samples detected below ML reported as non-detects

Frequent calibration verification within limits

IPR data reported

IPR aliquots meet required recovery criteria

SD of IPR series meet criteria

Method blank analyzed for each batch (minimum 1 every 10samples)

Method blank free from contamination

Field blank analyzed for each 10 samples per site

Field blanks free from contamination

MS/LCS contains hexadecane

MS/LCS contains stearic acid

MS/MSD performed at rate of one set per batch(1 set every 10 samples)

MS/MSD recoveries within specified windows

RPD within specified window

LCS/LCSD performed at rate of one set per batch(1 set every 10 samples)

LCS/LCSD recoveries within specified windows


Sample duplicates performed (1 every 10 samples)


Appropriate corrective action performed

List per excursion:

Statements of acceptance windows for recovery and RPDprovided

Acceptable results on at least annual PE samples

Sample taken as a grab in glass container without pre-rinsing

Holding time of 28 days met



Determination of Surfactants

Surfactants can be positive interferents in the oil & grease determination, inaddition to causing pollution problems in their own right. There are four commonprocedures that are used to generate information on the three classes ofsurfactants. The four techniques are the sublation separation, filtration of thesample through a ion exchange resin, methylene blue active substances (MBAS)measurement for anionic surfactants, and cobalt thiocyanate active substances(CTAS) measurement of nonionic surfactants. Cationic surfactants are notdetermined directly, instead, a by-difference technique is used.

The sublation apparatus (pictured in SM 5540B, and as Figure C-8 in Smith’sHandbook of Environmental Analysis) is a separation device. An inert gas isbubbled up through a 1 L sample of wastewater in the apparatus. Any surfactantsin the sample will be collected on the surface of the gas bubbles. Sodium chlorideis added to the sample to increase the ionic concentration to 10% to favorpartitioning of the surfactant out of the water. The gas then rises through a layer ofethyl acetate. The surfactants on the surface of the gas bubbles dissolve into theethyl acetate. The ethyl acetate layer is removed through the upper stopcock onthe apparatus. Two exchanges of ethyl acetate with 5 minutes of gas bubbling foreach exchange are sufficient to strip the sample of surfactants. The sublationapparatus is not available commercially. Laboratories that want to perform theprocedure have the apparatus custom fabricated by a local glassblower.Frequently, a glassblower can be found in the Chemistry Department of majoruniversities. Lily Glassworks in Smyrna, Georgia has successfully fabricated anumber of sublation devices, if a local glassblower cannot be found.

As an alternative to the sublation apparatus, any large buret with at least 1 Lcapacity can be used. A wide-bore chromatography tube with a fritted disk at thebottom is useful. The gas line is attached to the tip of the buret or tube, and ethylacetate layered over the top of the sample. Even a 1 L Erlenmeyer flask can beused. The gas line in this case is attached to one end of a fritted gas inlet tube,and the fritted end of the tube lowered through the sample to the bottom of theflask. Again several centimeters of ethyl acetate are layered over the surface ofthe wastewater sample to collect the surfactant. The ethyl acetate can be isolatedwith a pipette, or carefully poured into a small separatory flask to isolate thelayers.

Ethyl acetate is somewhat soluble in water and, if there are substantialamounts of alcohol or surfactants in the sample, can appear to completelydissolve in the sample if they are vigorously mixed or simply poured together. Theethyl acetate should be carefully added by gently pouring down the sides of thecontainer. This allows the lighter ethyl acetate to float on the water surface.

After the surfactants are isolated in the ethyl acetate, the solvent isevaporated by gently boiling the sample. Pure ethyl acetate boils at 77 °C andforms an azeotrope with water of 90% ethyl acetate composition that boils at70 °C. The means that any water in the sample is removed during the evaporation.If a hot plate is used as a heat source, the sample should be carefully watched.Ethyl acetate is not particularly toxic; however, it is flammable. The solid residueis weighed and contains the crude surfactant along with any other organicmaterial in the sample such as oil & grease.



The residue is next dissolved in methanol, then passed through an ion-exchange resin column. If an anion exchange resin is used, anionic surfactants areremoved. If a cation exchange resin is used, any cationic surfactants are removed.If a mixed-bed resin is used, both cationic and anionic surfactants are removedleaving only the nonionic surfactants plus any neutral oil and grease interferents.If the residue is weighed after both the sublation and the ion-exchange processes,the difference approximates the total of the cationic and anionic surfactants.Further subtraction of the MBAS result for anionic surfactants (See below.) fromthis total leaves an estimate of the cationic surfactants.

The methylene blue active substances test (MBAS, EPA Method 425.1 andSM 5540 C) is used to determine anionic surfactants in the sample. It can beperformed on either the raw sample or the sublated residue. The chemistry isbased on forming an organic soluble ion pair from the positive-charged methyleneblue molecule and the negative-charged anionic surfactant. The ion pair isextracted into chloroform, CHCl3, and the absorbance of the methylene blue inthe chloroform is determined colorimetically. The absorbance is related to thenumber of methylene blue molecules extracted into the organic solvent. These arerelated on a one-to-one basis to the number of anionic surfactant moleculesoriginally in the sample.

The results from the MBAS test are directly linked to the material used as astandard. The common standard is linear alkylbenzene sulfonate, LAS. The EPAhas, for many years, given laboratories an LAS standard of sodium laurylbenzenesulfonate with a stated molecular weight of 318 g/mol. This standard is no longeravailable from EPA. Replacement standards can be purchased from a variety ofchemical suppliers. Available are dodecylbenzenesulfonic acid, sodium salt, witha molecular weight of 348.5 (326.5 as the free acid), or sodium dodecyl sulfate(SDS or sodium lauryl sulfate) with a molecular weight of 288 (266 as the freeacid). Although these materials consist of a mixture of dodecyl (C12) isomers, allthe molecules have the same molecular weight.

The only problem with these standards is that anionic surfactants are not puresubstances of a defined molecular weight. Instead, the manufacturing processgenerates mixtures of substances with a range of molecular weights. Some of themolecules in lauryl-based anionic surfactant, previously provided by EPA, have aC12 tail while others in the mixture have tails ranging from C9 to C15. And not allanionic surfactants have tails that are lauryl-based. Some are based on palmitic orstearic acid with average molecular weights in the 400-500 g/mol range. Themixed anionic-nonionic surfactants have the polyether functions that can increasethe molecular weight into the thousands per molecule range.

The methylene blue (Basic Blue 9, Solvent Blue 8, CI 52015) that is used asthe color reagent in the MBAS test is not a pure material. It contains varyingamounts of active dye. It forms a more-or-less stable trihydrate depending on thelocal humidity. It is very sensitive to reducing agents and sulfide, which willdecolorize the dye. Samples can be pre-treated with small amounts of hydrogenperoxide to remove reductants and sulfide. Each time a new methylene bluereagent is prepared, a new calibration curve also needs to be prepared. Thecalibration must include extraction of known LAS standards. Simply dissolvingweighed amounts of the dye in chloroform to form colorimetric standards, whichhas been used as shortcut in some laboratories, is not a reliable technique.



There are a few interferences that complicate the MBAS test. Some anionscan cause initial partitioning of some of the dye into the organic layer.Backwashing the organic layer once with water tends to minimize thisinterference. Sulfide interference is mentioned above. Carboxylic acid-basedsoaps are insufficiently strong to form a tight ion pair with methylene blue and areleft in the water layer. Neutral organics may be extracted but will not contributean interference unless they absorb at the same wavelength as the methylene blueion pair, 652 nm. Extraction of an additional aliquot of the sample withoutmethylene blue creates a sample blank that can be used to correct for non-specific sample absorbance. Cationic surfactants may out-compete the methyleneblue for formation of ion pairs with the anionic surfactant molecules. These canbe removed by sublating the sample that has been acidified to pH 2, rather thanthe neutral to slightly basic pH indicated in the method (SM 5540B), then passingthe methanol solution of the residue through a cation-exchange resin to removeresidual cationics. After reconstitution in water, the MBAS extraction can beperformed.

Blanks, laboratory control samples, matrix spikes, and method detection limitstudies are straightforward and uncomplicated. The initial calibration calls for 10points. The calibration extractions can be miniaturized to save some time. A dailycalibration verification that includes the extraction of a known LAS standard isabsolutely necessary.

The cobalt thiocyanate active substances test (CTAS, SM 5540D) dependson the extraction of cobalt thiocyanate into an organic layer. Cobalt thiocyanate,Co(SCN)2, as a salt, is soluble in organic solvents such as chloroform andacetone, forming a blue solution. Water solutions of the salt are rose (red)colored. In the presence of both an organic solvent and water, the salt willpartition preferentially into the water.

The cobalt thiocyanate used in the method is actually the tetrathiocyanatocomplex of cobalt (II), [Co(SCN)4]2-, rather than the simple salt. The complex is,for the most part, not stable as a solid material, although the mercury salt is solid.The complex is made prior to use from ammonium thiocyanate, NH4SCN, andcobalt nitrate hexahydrate, Co(NO3)2•6H2O. There is a 21-times molar excess ofthiocyanate in the solution over that required for simple formation of thetetrathiocyanatocobaltate complex. In the presence of surfactants a competition isestablished between the surfactant and thiocyanate to chelate the cobalt. If thesurfactant molecule has at least six coordination sites (oxygen atoms) for thecobalt, the surfactant will win. The surfactant-cobalt complex will then partitioninto the organic layer. The absorbance of the cobalt in the organic layer is thendetermined colorimetrically at 620 nm.

Surfactant molecules that will successfully complex the cobalt must have atleast six POE or POP units, with better complexation occurring as the numberincreases. As is the case with the MBAS standards, the EPA for many years sup-plied laboratories with a nonionic standard with a specified activity. The standardwas composed of a mixture of C12-18E11 polyoxyethylene ethers with the tailranging from lauryl to stearyl. Because the EPA no longer supplies laboratorieswith the nonionic surfactant standard, commercial replacements must be found.The Brij surfactants are widely available as pure materials. These have a head of



10 POE (E10) with a variety of defined tail lengths. Brij 56, C16E10, also knownas 10 cetyl ether, has a molecular weight of 683. Brij 76, C18E10, also known as10 stearyl ether, has a molecular weight of 711. A pure C13E11, POE (11) tridecyl

alcohol ether, with a molecular weight of 684 is also available.6 Any of thesematerials is suitable as a replacement standard.

The cobalt center in the thiocyanato complex is sensitive to oxidation.Oxidants in the sample are generally removed through the sublation and mixedbed ion-exchange resin filtration. However, air contains oxygen, and the preparedreagent has a limited lifetime of about one month.

As with the MBAS procedure, quality control in the CTAS test for nonionicsurfactants is performed with blanks, laboratory control samples, matrix spikes,method detection limit determinations, and multi-point calibration with dailyverification. Sample results are reported in terms of mg/L CTAS, as the referencestandard.

The bottom line is that the analyst and the data user can not place too muchreliance upon the exact number obtained from either the MBAS test or the CTAStest, particularly when these numbers are used to establish mass-balances. It mustbe recognized that there is a dislocation between the result obtained frommolecule-counting and the actual mass of material in the sample. These errorsmay range up to a factor of 10 or more in some cases. In general, MBAS andCTAS results should be regarded as minimum estimates with the actual mass ofsurfactant in the sample being higher.

6 Chem Service Catalog number S-330, 1-800-452-9994, P.O. Box 3108, West Chester PA

19381-9941.



Surfactants Data Review Checklist

YES NO Review Item

Multipoint initial calibration performed

Daily calibration verification performed

All sample results reported within calibration range

List exceptions:

All samples sublated prior to determination


Initial calibration range includes ML/MDL



IPR data reported



Method blank analyzed for each batch(minimum 1 every 20 samples)













List per excursion:



Holding time of 48 hours met



Determination of Petroleum Hydrocarbons

There are a variety of names for petroleum hydrocarbon determinations. Thereare Total Petroleum Hydrocarbons (TPH), Total Recoverable Petroleum Hydro-carbons (TRPH), Diesel Range Organics (DRO), and Gasoline Range Organics(GRO). The DRO and GRO names are generally limited to determinations thatuse gas chromatography as the analytical technique. TPH is sometimes meant tocover both DRO and GRO; however, just as often, what is meant is an extractiontechnique followed by either a residue weighing or an infrared absorbance (IR)determination. TRPH normally refers to an extraction-IR technique; however,again, the use is sloppy and what is meant is not necessarily what is understood.

Within the context of oil & grease determinations, petroleum hydrocarbonsform an important sub-group, and a specific result that can be assigned to thissub-group is frequently needed. Petroleum hydrocarbons are characterized as non-polar molecules composed of only carbon and hydrogen. They can be defined asall materials in the oil and grease residue that will not be adsorbed by a polarsorbent, silica gel being the most frequent choice of sorbent. The technique (SM5520F and EPA Method 1664) is to add 3.0 g of silica gel to a hexane solution ofthe oil & grease residue, filter off the silica gel, evaporate to dryness, and weighthe residue.

One of the major causes of variation that arise from the performance of thismethod lies with the silica gel. Silica gel is precipitated silicic acid, H2SiO3. Allsilicon atoms in the material are not fully in this form. There is some polymericsilica, SiO2, and various grades of silica gel will have differing proportions. Silicagel comes in a variety of mesh sizes. A chromatography grade silica gel will havevery large particles, which allow a column to be packed while still allowingadequate passage of solvent through the column. Silica gel suitable for petroleumhydrocarbon determinations should have a much smaller particle size, normally100-200 mesh, and a correspondingly higher surface area suitable for maximumadsorption.

Silica gel is a polar material. It will adsorb other polar materials uponcontact. During the manufacturing and packaging process it can becomecontaminated with organic materials. The analyst should not assume that thepurchased silica gel is clean. Silica gel is slightly soluble in methanol. Pre-washing the silica gel with some methanol will strip-off any contaminatingorganics, as well as activate the surface of the adsorbent. Following the methanolwash with a hexane rinse will assure clean, active silica gel. Hexane isflammable, and the analyst should exercise due caution in the subsequent dryingof the silica gel.

Silica gel is very hygroscopic. Packets of silica gel are frequently found inpackaged electronics and pharmaceuticals to control the humidity. Wateradsorbed to silica gel occupies the polar binding sites that the analyst isdepending upon to remove the non-petroleum hydrocarbon materials from the oil& grease residue. Silica gel, regardless of source, should be dried at 104 °C for atleast 24 hours prior to use. If silica gel must be stored before use, it should bedried then immediately placed in a desiccator charged with phosphorus pentoxide.Phosphorus pentoxide is one of the few materials that can out-compete the silica



gel for water. Calcium sulfate, Drierite®, is completely ineffective for thispurpose.

Silica gel is provided in bulk and pre-packaged in short glass and plasticcolumns. The bulk material is easier to clean and dry, and more suitable for thepetroleum hydrocarbon procedure.

Three grams of a properly cleaned, activated, dried, and stored silica gel ofthe appropriate mesh size will completely adsorb up to 100 mg of polar materialfrom a hexane solution. Inadequately prepared silica gel will require repeatedtreatments of the hexane solution to strip the polar materials.

The quality controls associated with EPA Method 1664 follow into thepetroleum hydrocarbon determination. The true values of the matrix spike andlaboratory control samples are going to be half those used for the oil & greasedetermination, due to the complete adsorption of the stearic acid component.

IR determination of petroleum hydrocarbons (EPA Method 418.1, SM 5520C)is based on the C-H absorption of IR light at 2930 cm-1. The technique obviouslydepends upon using an extraction solvent that lacks IR absorption at thisfrequency. Freon 113 fits the requirements, and the method was widely used overthe last 20 years. Other solvents that fit the requirement are carbon tetrachlorideand tetrachloroethene, each with its own set of problems. The technique has beenphased out along with the Freon 113 usage.

Gas chromatographic determination (Lecture 4) of petroleum hydrocarbonshas centered upon using the purge & trap GC with either FID or MS detector forgasoline range organics and the extraction/direct injection technique with FID orMS detector for the diesel range organics. Straight chain alkanes have beenwidely used to delineate the boiling point ranges and thus identify the variouspetroleum products (Tables 15-3 and 15-4). Quantitation has been determined bysumming the areas of key peaks, or by summing all area above the baselinebetween certain retention times. External and internal standards have been used.See Smith’s Handbook of Environmental Analysis, Third Edition for a morecomplete discussion.

Table 15-4. Boiling points of common hydrocarbon standards

Hydrocarbon Carbon number BP °CPropane 3 -42.1

n-Butane 4 -0.5

n-Pentane 5 35-36

n-Hexane 6 69

Cyclohexane 6 80.7

Benzene 6 80

n-Heptane 7 98

Methylcyclohexane 7 101

Toluene 7 111

n-Octane 8 125-127

Ethylbenzene 8 136



Table 15-4. Boiling points of common hydrocarbon standards, continued

Hydrocarbon Carbon number BP °Cp-Xylene 8 138

n-Nonane 9 151

n-Decane 10 174

Decalin (c and t) 10 189-193

Naphthalene 10 218

n-Undecane 11 196

n-Dodecane 12 216

n-Tridecane 13 234

n-Tetradecane 14 252-254

Anthracene 14 342

n-Pentadecane 15 270

n-Hexadecane 16 284

n-Heptadecane 17 302

n-Octadecane 18 317

n-Nonadecane 19 330

n-Eicosane 20 343

n-Heneicosane 21 356

n-Docosane 22 369

n-Tricosane 23 380

n-Tetracosane 24 391

n-Pentacosane 25 402

n-Hexacosane 26 412

n-Heptacosane 27 422

n-Octacosane 28 432

n-Nonacosane 29 441

n-Triacontane 30 450

n-Hentriacontane 31 458



Petroleum Hydrocarbons Data Review Checklist

YES NO Review Item

Analytical balance checked twice each day with 2 and 1000 mgstandard

No subsamples taken from sample container

Silica gel properly cleaned, activated, and dried prior to use




IPR data reported



Method blank analyzed for each batch(minimum 1 every 10 samples)




MS/LCS contains hexadecane

MS/LCS contains stearic acid










List per excursion:



Maximum holding time of 28 days met



References

Berger, W., H. McCarty, and R.-K. Smith, 1996. Environmental Laboratory DataEvaluation, Genium Publishing, Schenectady, NY.

Cotton, F.A., and G. Wilkinson, 1988. Advanced Inorganic Chemistry, FifthEdition, Wiley Interscience, New York, NY.

Eaton, A., L. Clesceri, and A. Greenberg, 1995. Standard Methods for theExamination of Water and Wastewater, 19th Edition, APHA, AWWA, and WEF,Washington, DC. Previous Editions are also referenced.

Flaschka, H.A., A.J. Bernard, Jr., and P.E. Sturrock, 1980. Quantitative AnalyticalChemistry, Second Edition. Willard Grant Press, Boston, MA.

Hanahan, D. J., 1997. A Guide to Phospholipid Chemistry. Oxford University Press,New York, NY.

Sawyer, C.L., P.L. McCarty, and G.E. Parkin, 1994. Chemistry for EnvironmentalEngineering, Fourth Edition. McGraw-Hill, New York, NY.

Smith, R,-K., 1996. Water and Wastewater Laboratory Techniques, WaterEnvironment Federation, Alexandria, VA.

Smith, R.-K., 1997. Handbook of Environmental Analysis, Third Edition, GeniumPublishing, Schenectady, NY.

Stumm, W., and J.J. Morgan, 1996. Aquatic Chemistry, Third Edition. John Wiley& Sons, New York, NY.

Lecture 15 Oil, Grease, Surfactants, and Hydrocarbons

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Transcript of Lecture 15 Oil, Grease, Surfactants, and Hydrocarbons