The Effects of Easily Ionizable Elements (EIE) in Axially ... · VHG Labs Standards and Supplies...

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The Effects of Easily Ionizable Elements (EIE)The Effects of Easily Ionizable Elements (EIE)in Axially Viewed Inductively Coupled Plasma-in Axially Viewed Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) inAtomic Emission Spectroscopy (ICP-AES) inOrganic Matrices during the Analysis of MetalsOrganic Matrices during the Analysis of Metalsin New and Used Oilsin New and Used Oils

Tim Alavosus, Ph.D., VHG LabsTim Alavosus, Ph.D., VHG Labs

Dave Hilligoss, Perkin ElmerDave Hilligoss, Perkin Elmer

The Pittsburgh Conference and Exhibition26 February 2007

Introduction

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Matrix effects can occur in all plasmas, toMatrix effects can occur in all plasmas, tovarying degrees, and may vary greatly basedvarying degrees, and may vary greatly basedon a wide range of variables, includingon a wide range of variables, includinginstrument design, operating conditions,instrument design, operating conditions,sample introduction techniques, and more.sample introduction techniques, and more.

These effects are common to a plasma,These effects are common to a plasma,regardless of its viewing configuration, axialregardless of its viewing configuration, axialor radial. or radial. However, they manifest themselvesHowever, they manifest themselvesdifferently depending on the view.differently depending on the view.

Introduction

Due to the inherent nature of orthogonally viewing a plasmaDue to the inherent nature of orthogonally viewing a plasmaradially in ICP-AES, many of these effects are often notradially in ICP-AES, many of these effects are often notpronounced to a degree high enough to be of consequencepronounced to a degree high enough to be of consequenceduring most common applications of the technique.during most common applications of the technique.

Usually, the operator may select viewing regions which areUsually, the operator may select viewing regions which arehighly void of these effects, at least to a degree which ishighly void of these effects, at least to a degree which isacceptable for the analysis.acceptable for the analysis.

Radial vs. Axial Viewing

However, viewing of the plasma along the z-axis (i.e.,However, viewing of the plasma along the z-axis (i.e.,axially) inherently requires a view through the entireaxially) inherently requires a view through the entireplasma, and with it, all associated plasma-related effects.plasma, and with it, all associated plasma-related effects.

You are essentially You are essentially ““looking down the barrel of a gunlooking down the barrel of a gun””,,through the entire plasma sample excitation zone. Youthrough the entire plasma sample excitation zone. Yousee all of the effects on the plasma, all of the time.see all of the effects on the plasma, all of the time.

Radial vs. Axial Viewing

Of particular interest is the study of the effects ofOf particular interest is the study of the effects ofthe presence of effectively large amounts ofthe presence of effectively large amounts ofEasily Ionizable Elements (Easily Ionizable Elements (EIEEIE’’ss) on the emission) on the emissionof other elements in the plasma.of other elements in the plasma.

These effects are well documented for samples inThese effects are well documented for samples inalkali and other high-salt alkali and other high-salt aqueous matricesaqueous matrices..

Why We’re Here Today – EIE’s

E I E OI

Due to the nature of analysis of certain types ofDue to the nature of analysis of certain types oforganic (oil-based) matrices containing wearorganic (oil-based) matrices containing wearmetals, this effect was rarely encountered, asmetals, this effect was rarely encountered, asthere is usually too small a quantity of there is usually too small a quantity of EIEEIE’’ss in inthe sample.the sample.

However, recently, there has been heightenedHowever, recently, there has been heightenedinterest in the analysis of petroleum oilsinterest in the analysis of petroleum oilscontaining additives packages, including Ca, Mg,containing additives packages, including Ca, Mg,and other elements known to cause EIE effects.and other elements known to cause EIE effects.This has created a new interest in the study ofThis has created a new interest in the study ofEIE effects in organic matrices.EIE effects in organic matrices.

EIE’s in Oils

In this paper, we examine these effects andIn this paper, we examine these effects andreport their causes as well as suggestions forreport their causes as well as suggestions foracceptable corrective actions.acceptable corrective actions.

EIE’s in Oils

Easily Ionizable Elements are,Easily Ionizable Elements are,well, just that.well, just that.

As you might expect, they areAs you might expect, they aremostly the Group I and II alkalis,mostly the Group I and II alkalis,along with some others.along with some others.

Essentially, they have theEssentially, they have theeffect of adding additionaleffect of adding additionalelectron density to the plasma,electron density to the plasma,which can be important if theywhich can be important if theyare present in high enoughare present in high enoughconcentrations.concentrations.

Easily Ionizable Elements

MM00 M M++ + e + e--

Ionization Equilibrium

This equilibrium is very important.This equilibrium is very important.

We must consider atomic (MWe must consider atomic (MII) and ionic (M) and ionic (MIIII))emissions.emissions.

If an EIE is added, in large enough quantity, toIf an EIE is added, in large enough quantity, tothe plasma, then this equilibrium the plasma, then this equilibrium –– and thus the and thus theresulting emission resulting emission –– can be upset, giving false can be upset, giving falseresults.results.

MMII M MIIII + e + e--

Ionization Equilibrium

So, if youSo, if you’’re looking at an atom wavelength, and are looking at an atom wavelength, and alot of lot of EIEEIE’’ss (and consequently, more electrons) (and consequently, more electrons)are added, the equilibrium can shift to the left,are added, the equilibrium can shift to the left,giving an abnormally high amount of Mgiving an abnormally high amount of MII species, species,and accordingly, more Mand accordingly, more MII emission emission –– resulting in resulting inimproperly high readings for that metal.improperly high readings for that metal.

+ e+ e--MMI I ++ MMIIII

Matrix Effects on the Plasma

Things to consider in the study of matrixThings to consider in the study of matrixeffects on a plasma:effects on a plasma:

1. Sample Introduction• Nebulizer• Spray chamber• Desolvation system (if applicable)• Aerosol drop size distribution• Analyte and solvent transport rates• Thermal properties and background• Chemistry issues (polarity, acid/base, etc.)

2. Instrument Variables• Nebulizer gas flow rate • RF power• Plasma observation zone• Plasma viewing mode• Other (mirrors, shear gas, etc.)

Matrix Effects the Plasma

More to consider in the study of matrix effectsMore to consider in the study of matrix effectson a plasma:on a plasma:

3. Interfering Element• Single element solutions• Multi element solutions• Interfering element concentration• Analyte line properties

4. Multiple Interfering Elements• Combined effects – linear (additive) or other?

5. Use of an Internal Standard

EIE Effects to Consider

All of the previously mentioned effects areAll of the previously mentioned effects areimportant. For the purposes of this paper, weimportant. For the purposes of this paper, wewill concern ourselves primarily with:will concern ourselves primarily with:3. Interfering Element

• Single element solutions• Multi element solutions• Interfering element concentration• Analyte line properties (simply atom or ion)

4. Multiple Interfering Elements• Combined effects – linear (additive) or other?

5. Use of an Internal Standard – Does it help?

All of the early studies of All of the early studies of EIEEIE’’ss ( (MermetMermet,,HieftjeHieftje, , HorlickHorlick, many others) was, many others) wasperformed in aqueous media.performed in aqueous media.

Although there were conflicting accounts inAlthough there were conflicting accounts inthe literature*, it was fairly consistentlythe literature*, it was fairly consistentlyagreed upon that the order of interferenceagreed upon that the order of interferenceeffect in aqueous solution was:effect in aqueous solution was:

Ca > Mg > Na > KCa > Mg > Na > K

Previous Work

**HorlickHorlick referred to referred to EIEEIE’’ss as a as a ““study in confusion.study in confusion.””

We needed to see what would happen in oils.We needed to see what would happen in oils.

We examined the effects of 5 elements that canWe examined the effects of 5 elements that canbe commonly found in relatively highbe commonly found in relatively highconcentrations in todayconcentrations in today’’s New and Used motors New and Used motoroils (typical high ranges in parentheses):oils (typical high ranges in parentheses):

Ba (1000 Ba (1000 µµg/g)g/g)

Ca (3000 Ca (3000 µµg/g)g/g)

Mg (1000 Mg (1000 µµg/g)g/g)

P (2000 P (2000 µµg/g)g/g)

ZnZn (1000 (1000 µµg/g)g/g)

Our Work

If the presence of these elements in a highIf the presence of these elements in a highenough concentration could be found toenough concentration could be found tohave an effect on the values determinedhave an effect on the values determinedfor other elements, it could significantlyfor other elements, it could significantlyaffect the action required in follow-upaffect the action required in follow-up

For example, if a particular element in aFor example, if a particular element in aused oil sample was improperlyused oil sample was improperlydetermined to be at a high enough level, itdetermined to be at a high enough level, itcould trigger an corrective actioncould trigger an corrective actionrequirement for many engine (or other)requirement for many engine (or other)components.components.

Ba, Ca, Mg, P, Zn

We ran a series of experiments toWe ran a series of experiments todetermine if there were any EIE effectsdetermine if there were any EIE effectsfound with either radial or axial viewing offound with either radial or axial viewing ofthe plasma in oil-based media with Ba, Ca,the plasma in oil-based media with Ba, Ca,Mg, P, and Zn at high concentration levelsMg, P, and Zn at high concentration levelsthat are commonly found in todaythat are commonly found in today’’s news newand used oils.and used oils.

The elements examined for possible effectThe elements examined for possible effectincluded the included the ““V21+KV21+K”” common to oils common to oilsanalysis (Ag, Al, B, Ba, Ca, Cd, Cr, Cu, Fe,analysis (Ag, Al, B, Ba, Ca, Cd, Cr, Cu, Fe,K, Mg, Mn, Mo, Na, Ni, P, Pb, Si, Sn, Ti, V,K, Mg, Mn, Mo, Na, Ni, P, Pb, Si, Sn, Ti, V,Zn)Zn)

EIE Experiments in Oil-Based Media

Set 1: CalibrationSet 1: Calibration BlankBlank

V21+K 100 V21+K 100 µµg/g (ppm) g/g (ppm) (Used for calibration and QC)(Used for calibration and QC)

Set 2: 1000 Set 2: 1000 µµg/g pure Ba, Ca, Mg, P, Zn (separate)g/g pure Ba, Ca, Mg, P, Zn (separate) 1000 1000 µµg/g g/g BaBa

1000 1000 µµg/g g/g CaCa

1000 1000 µµg/g g/g MgMg

1000 1000 µµg/g g/g PP

1000 1000 µµg/g g/g ZnZn

Experimental Solutions*:

*A Co Internal Standard was used for all analyses*A Co Internal Standard was used for all analyses

Set 3: V21+K 100 Set 3: V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g each (separate)g/g each (separate) V21+K 100 V21+K 100 µµg/g + 1000 Bag/g + 1000 Ba

V21+K 100 V21+K 100 µµg/g + 1000 Cag/g + 1000 Ca

V21+K 100 V21+K 100 µµg/g + 1000 Mgg/g + 1000 Mg

V21+K 100 V21+K 100 µµg/g + 1000 Pg/g + 1000 P

V21+K 100 V21+K 100 µµg/g + 1000 Zng/g + 1000 Zn

Set 4: V21+K 100 Set 4: V21+K 100 µµg/g + varying Cag/g + varying Ca V21+K 100 V21+K 100 µµg/g + 1000 Cag/g + 1000 Ca

V21+K 100 V21+K 100 µµg/g + 2000 Cag/g + 2000 Ca

V21+K 100 V21+K 100 µµg/g + 3000 Cag/g + 3000 Ca

V21+K 100 V21+K 100 µµg/g + 4000 Cag/g + 4000 Ca

V21+K 100 V21+K 100 µµg/g + 5000 Cag/g + 5000 Ca

Experimental Solutions:

Set 5: V21+K Varying [ ] + 5000 Ca Set 5: V21+K Varying [ ] + 5000 Ca µµg/gg/g V21+K 10 V21+K 10 µµg/g + 5000 Cag/g + 5000 Ca

V21+K 30 V21+K 30 µµg/g + 5000 Cag/g + 5000 Ca

V21+K 50 V21+K 50 µµg/g + 5000 Cag/g + 5000 Ca

V21+K 100 V21+K 100 µµg/g + 5000 Cag/g + 5000 Ca

V21+K 500 V21+K 500 µµg/g + 5000 Cag/g + 5000 Ca

Set 6: V21+K 100 Set 6: V21+K 100 µµg/g + Ba, Ca, Mg, P,g/g + Ba, Ca, Mg, P,Zn all 1000 Zn all 1000 µµg/gg/g

V21+K 100 V21+K 100 µµg/g + Ba 1000 g/g + Ba 1000 µµg/g, Ca 1000 g/g, Ca 1000 µµg/g,g/g,Mg 1000 Mg 1000 µµg/g, P 1000 g/g, P 1000 µµg/g, Zn 1000 g/g, Zn 1000 µµg/gg/g

Experimental Solutions:

Perkin-Elmer Optima 5300 DV (Dual-View)Perkin-Elmer Optima 5300 DV (Dual-View)

Instrumentation

Dual View

K = 766.490 nmK = 766.490 nm

Mg = 285.213 nmMg = 285.213 nm

Al = 394.401 nmAl = 394.401 nm

Na = 588.995 nmNa = 588.995 nm

(All are (All are ““II””(1) or atom wavelengths)(1) or atom wavelengths)

Wavelengths Used

All experiments were run using both axial and radialAll experiments were run using both axial and radialviews on the same instrument.views on the same instrument.

All were run with two different nebulizers, cross-flowAll were run with two different nebulizers, cross-flowtype and concentric.type and concentric.

All solutions were hand-diluted gravimetrically to 1/10All solutions were hand-diluted gravimetrically to 1/10with solvent immediately prior to use.with solvent immediately prior to use.

Samples were run using an automated sampling device.Samples were run using an automated sampling device.

QC check standards included a blank and 100 QC check standards included a blank and 100 µµg/g.g/g.These were run at a minimum frequency of every 10These were run at a minimum frequency of every 10samples, and in all cases passed a +/- 10% thresholdsamples, and in all cases passed a +/- 10% threshold(+/- 10 (+/- 10 µµg/g for the blank).g/g for the blank).

Experimental Notes

Set 2: 1000 Set 2: 1000 µµg/g pure Ba, Ca, Mg, P, Zn (separate)g/g pure Ba, Ca, Mg, P, Zn (separate)

1000 1000 µµg/g g/g BaBa

1000 1000 µµg/g g/g CaCa

1000 1000 µµg/g g/g MgMg

1000 1000 µµg/g g/g PP

1000 1000 µµg/g g/g ZnZn

Radial ViewRadial View: No significant* change for any element was: No significant* change for any element wasrecorded, for any of the above samples.recorded, for any of the above samples.

Axial ViewAxial View: No significant* change for any element was: No significant* change for any element wasrecorded, for any of the above samples.recorded, for any of the above samples.

Results

**““SignificantSignificant”” = > +/- 5% = > +/- 5%

Set 3: V21+K 100 Set 3: V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g each (separate)g/g each (separate) V21+K 100 V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g Bag/g Ba

V21+K 100 V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g Cag/g Ca

V21+K 100 V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g Mgg/g Mg

V21+K 100 V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g Pg/g P

V21+K 100 V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g Zng/g Zn

Radial ViewRadial View: No significant* change for any element was: No significant* change for any element wasrecorded, for any of the above samples.recorded, for any of the above samples.

Axial ViewAxial View: 1000 : 1000 µµg/g Mg returned values of g/g Mg returned values of Ca 112Ca 112µµg/g, and Na 110g/g, and Na 110..

1000 1000 µµg/g Ba returned values of g/g Ba returned values of Na 116 Na 116 µµg/g, K 120g/g, K 120µµg/g, Ca 107 g/g, Ca 107 µµg/g, and Al 110 g/g, and Al 110 µµg/gg/g..

1000 1000 µµg/g Ca returned values of g/g Ca returned values of Na 112 Na 112 µµg/g, and Mgg/g, and Mg103 103 µµg/gg/g (will demonstrate significance later herein).(will demonstrate significance later herein).

Results


Set 4: V21+K 100 Set 4: V21+K 100 µµg/g + varying Ca: g/g + varying Ca: RADIAL VIEWRADIAL VIEW V21+K 100 V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g Cag/g Ca





NO SIGNIFICANT* CHANGES OBSERVEDNO SIGNIFICANT* CHANGES OBSERVED

Results


Set 4: V21+K 100 Set 4: V21+K 100 µµg/g + varying Ca: g/g + varying Ca: AXIAL VIEWAXIAL VIEW V21+K 100 V21+K 100 µµg/g + 1000 g/g + 1000 µµg/g Cag/g Ca





Results

V21+K 100 V21+K 100 µµg/g + Ca @:g/g + Ca @:

Affected Analyte:Affected Analyte:

1101511411145000

1081341301104000

1061261261083000

1051301101072000

1031121031041000

1001001001000

MgNaKAl

Results

V21+K 100 µg/g + Ca @ rising [ ] AXIAL VIEW

0

20

40

60

80

100

120

140

160

0 1000 2000 3000 4000 5000 6000

[Ca]

Al

K

Na

Mg

Set 5: V21+K Varying [ ] + 5000 Ca Set 5: V21+K Varying [ ] + 5000 Ca µµg/g g/g RADIAL VIEWRADIAL VIEW V21+K 10 V21+K 10 µµg/g + 5000 g/g + 5000 µµg/g Cag/g Ca





Results

Ca 5000 Ca 5000 µµg/g + V21+K @:g/g + V21+K @:


500535525500500

100101100100100

5053515050

3030303030

1010101010

00000

MgNaKAl

Ca 5000 + Varied [V21+K] RADIAL VIEW

0

100

200

300

400

500

600

0 100 200 300 400 500 600

[Gravimetric]

[Mea

sure

d] Al

K

Na

Mg

Results

m(Km(K) = 1.0(5)) = 1.0(5)

m(Alm(Al) = 1.0) = 1.0

m(Nam(Na) = 1.0(7)) = 1.0(7)

m(Mgm(Mg) = 1.0) = 1.0

Set 5: V21+K Varying [ ] + 5000 Ca Set 5: V21+K Varying [ ] + 5000 Ca µµg/g g/g AXIAL VIEWAXIAL VIEW V21+K 10 V21+K 10 µµg/g + 5000 g/g + 5000 µµg/g Cag/g Ca





Results

Ca 5000 Ca 5000 µµg/g + V21+K @:g/g + V21+K @:


(N/A)(N/A)708575500

110151141114100

5472635450

3347373330

1118121010

00000

MgNaKAl

Results

Ca 5000 + Varied [V21+K] AXIAL VIEW

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600

[Gravimetric]

[Mea

sure

d] Al

K

Na

Mg

m(Km(K) = 1.4) = 1.4

m(Alm(Al) = 1.2) = 1.2

m(Nam(Na) = 1.5) = 1.5

m(Mgm(Mg) = 1.1) = 1.1

Set 6: V21+K 100 Set 6: V21+K 100 µµg/g + Ba, Ca, Mg, P, Zn all 1000g/g + Ba, Ca, Mg, P, Zn all 1000µµg/gg/g

V21+K 100 V21+K 100 µµg/g + Ba 1000 g/g + Ba 1000 µµg/g, Ca 1000 g/g, Ca 1000 µµg/g, Mg 1000g/g, Mg 1000µµg/g, P 1000 g/g, P 1000 µµg/g, Zn 1000 g/g, Zn 1000 µµg/gg/g

Radial ViewRadial View: No significant* change for any: No significant* change for anyelement was recorded, for any of the aboveelement was recorded, for any of the abovesamples.samples.

Axial ViewAxial View: A small effect was noted on Sodium: A small effect was noted on Sodium(Na = 121 (Na = 121 µµg/g) (Consistent from previous Ca 1000g/g) (Consistent from previous Ca 1000µµg/g results)g/g results)

Results


The effect of the presence of relativelyThe effect of the presence of relativelyhigh concentrations of Easily Ionizablehigh concentrations of Easily IonizableElements (Elements (EIEEIE’’ss) in samples is) in samples isobserved in the analysis of oil-basedobserved in the analysis of oil-basedmaterials for both radial and axial-materials for both radial and axial-viewed plasmas.viewed plasmas.

This effect is much more pronouncedThis effect is much more pronouncedfor axial-viewed configurations.for axial-viewed configurations.

Conclusions

Of the 5 elements often found inOf the 5 elements often found inrelatively high concentrations in newrelatively high concentrations in newand used motor oils (Ba, Ca, Mg, P,and used motor oils (Ba, Ca, Mg, P,and Zn), Ca showed significant effectsand Zn), Ca showed significant effectsin a range of 1000 in a range of 1000 –– 5000 5000 µµg/g and Bag/g and Bashowed potential promise at 1000 showed potential promise at 1000 µµg/g,g/g,during axial viewing.during axial viewing.

The primary elements affected areThe primary elements affected areother other EIEEIE’’ss; here, we have found ; here, we have found KK, , MgMg,,NaNa, and perhaps surprisingly , and perhaps surprisingly AlAl, to be, to beaugmented.augmented.

Conclusions

The findings are significant; for example,The findings are significant; for example,the the ““trigger pointtrigger point”” for the increased for the increasedevaluation of certain engines is often 25evaluation of certain engines is often 25µµg/g Na or K (indicating a coolant leakg/g Na or K (indicating a coolant leakand requiring at minimum furtherand requiring at minimum furthertesting).testing).

An unwarranted increase of this valueAn unwarranted increase of this value(25 (25 µµg/g) or more was found to beg/g) or more was found to bepotentially caused simply by EIE effectspotentially caused simply by EIE effectsduring axial viewing.during axial viewing.

Conclusions

If the relative slope (m) of theIf the relative slope (m) of theaffectation of the elements can be usedaffectation of the elements can be usedas a measure of their susceptibility toas a measure of their susceptibility toan EIE, here, using Ca at 5000 an EIE, here, using Ca at 5000 µµg/g,g/g,the order of augmentation is:the order of augmentation is:

Na (1.5)Na (1.5)

K (1.4)K (1.4)

Al (1.2)Al (1.2)

Mg (1.1)Mg (1.1)

Conclusions

If axially viewing oil-based materialsIf axially viewing oil-based materialsthat contain high amounts of that contain high amounts of EIEEIE’’ss,,serious consideration MUST be given toserious consideration MUST be given totheir potential effects.their potential effects.

Conclusions

Repeat the same experiments with ionRepeat the same experiments with ionwavelengths for Na, Mg, Al, K. See a decrease?wavelengths for Na, Mg, Al, K. See a decrease?

Repeat the V21+K Varied [ ] + 5000 Repeat the V21+K Varied [ ] + 5000 µµg/g Cag/g Caexperiments with Ba, Na, Mg, K, Al, (others?)experiments with Ba, Na, Mg, K, Al, (others?)

Repeat the V21+K 100 Repeat the V21+K 100 µµg/g + Varied [ ] Cag/g + Varied [ ] Caexperiments with Ba Na, Mg, K, Al (others?)experiments with Ba Na, Mg, K, Al (others?)

Repeat the above with combinations of Ba, Na,Repeat the above with combinations of Ba, Na,Mg, Al (others?) to determine if effect is linear orMg, Al (others?) to determine if effect is linear orother based on % EIE component.other based on % EIE component.

Is it possible to create some form of Is it possible to create some form of ““ExpectedExpectedEIE EffectEIE Effect”” table for a given model ICP? table for a given model ICP?

Future Work:

The End

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Thank You.

For more information, please contact:

Tim AlavosusVHG Labs276 Abby Rd.Manchester, NH 03053(+1) [email protected]

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