Environmental Series - US EPA SW-846Method 6010 using an iCAP 6500 Duo

Introduction

This application note describes the performance of theThermo Scientific iCAP 6500 Duo for the analysis ofenvironmental sample types by the US EPA method 6010.The method is suitable for the determination of 31 elementsin ground waters, TCLP & EP extracts, industrial andorganic wastes, soils, sludges, and sediments. All samplesexcept filtered groundwater must be digested prior toanalysis using EPA method 3050b or similar. This methodand its variants are widely used for the analysis ofenvironmental samples in North American and worldwidelaboratories and the ability to undertake this type ofanalysis using such method therefore represent an importantbenchmark for any ICP instrument.

ExperimentalThe Thermo Scientific iCAP 6000 series uses a ChargeInjection Device (CID) detector, which offers a greaterphotosensitive area than previous generation CIDdetectors and than other chip-based ICP detectortechnologies and consequently offers lower noise forimproved detection limits and better stability.

The CID detector is a non-blooming device, meaningthat low-level signals measured at pixels adjacent to areasof the chip receiving high light intensity are not affectedby the signal 'over-spill' that can cause problems withfalse-positive detection that can occur with some othertypes of chip-based detection technologies. The iCAPtherefore has the ability to measure high concentrations ofmatrix elements and low levels of contaminants at thesame time without saturation.

A Thermo Scientific iCAP 6000 was used to analyzevarious environmental samples types within the qualitycontrol framework of US EPA method 6010.

Instrument conditions used for analysis are shown inTable 1 below.

Parameter Setting

Nebulizer Glass ConcentricSpray Chamber Glass CyclonicCenter tube 2 mmPump tubing ( Tygon) Sample Drain

Orange- White White-WhiteNebulizer Gas Flow 0.7 l/minPlasma Gas Flow 12 l/minAuxiliary Gas Flow 0.5 l/minRF Power 1150 WSample Flush Time 45 sPump Speed 45 rpmIntegration Time Low (166 -230 nm) High (230-847 nm)

15 s 5 s

Table 1: Instrument Parameters used for the analysis

Calibration standards were prepared in 5 % v/vhydrochloric acid (HCl) and 1 % v/v nitric acid (HNO3)at element concentrations selected to cover the desiredrange for each element. Elements were separated asspecified in method 6010 to minimize interference.Quality control solutions were run at the intervalsspecified by the method and any necessary correctiveactions were taken automatically using programmedsoftware interventions. The iCAP 6500 Duo allows forelements expected at low concentration to be read axiallywhere the best sensitivity is required. The radial view wasused for elements at higher concentrations or for thoseelements that suffer from easily-ionized element interference.An internal standard of 5 ppm scandium was automaticallyadded on-line with the internal standard mixing kit. Detailsof wavelengths and plasma views for each of the analytesand internal standard elements are shown in Table 2. Theanalyte elements were referenced to an internal standardwavelength on the same slit and plasma view.

Key Words

• ICP

• iCAP 6500

• EnvironmentalAnalysis

• SW-846 Method6010b

• US-EPA

ApplicationNote: 40836

Thermo Scientific: Your partner for enhanced environmental analysisFor information on other Thermo Scientific offerings for environmental trace element analysis or

to keep up to date with legislative and environmental analysis developments,please visit our Environmental Resource Centre (ERC) at www.thermo.com/erc

Element Wavelength (nm) Plasma View Internal Standard

Ag 328.068 Axial Sc 361.384 nmAl 308.215 Radial Sc 361.384 nmAs 189.042 Axial Sc 227.318 nmBa 455.403 Radial Sc 361.384 nmBe 313.107 Radial Sc 361.384 nmCa 315.887 Radial Sc 361.384 nmCd 214.438 Axial Sc 227.318 nmCo 228.616 Axial Sc 227.318 nmCr 267.716 Axial Sc 361.384 nmCu 324.754 Axial Sc 361.384 nmFe 271.441 Radial Sc 361.384 nmK 766.490 Radial Sc 631.384 nmMg 279.079 Radial Sc 361.384 nmMn 260.569 Axial Sc 361.384 nmNa 589.592 Radial Sc 361.384 nmNi 231.604 Axial Sc 227.318 nmPb 220.353 Axial Sc 227.318 nmSb 206.833 Axial Sc 227.318 nmSe 196.090 Axial Sc 227.318 nmTl 190.856 Axial Sc 227.318 nmV 292.402 Axial Sc 361.384 nmZn 206.200 Axial Sc 227.318 nm

Table 2: Element Wavelengths

Significant interference from spectral overlaps can beobserved due to the complex nature of the matrix forthese types of samples. Major elements, such as Al, Ca,Fe, Mg, Si and P were checked for spectral contributionson other analyte elements during method development.Once the interfering elements were identified, high-puritysingle element solutions were measured and theinstrument software automatically calculated interferencecorrection factors using the Interfering Element Correction(IEC) function of iTEVA software. Interferences observedare shown in Table 3.

Element Wavelength (nm) Interfering Elements

Ag 328.068 -Al 308.215 -As 189.042 Al, FeBa 455.403 -Be 313.107 -Ca 315.887 -Cd 214.438 Al, FeCo 228.616 -Cr 267.716 -Cu 324.754 FeFe 271.441 -K 766.490 -Mg 279.079 -Mn 260.569 -Na 589.592 -Ni 231.604 -Pb 220.353 Al, FeSb 206.833 Al, FeSe 196.090 Al, FeTl 190.856 Al, FeV 292.402 -Zn 206.200 -

Table 3: Interelement Interferences

Analysis Results

Initial Performance ChecksMethod detection limits (MDLs) were established bymeasuring a blank solution (5 % HCl, 1 % HNO3). Thesolution was analyzed seven times with each analysishaving three replicates, the mean of 3x the standarddeviation value from all of the runs was calculated.Results obtained are given in Table 4.

Element Wavelength (nm) Plasma View MDL (ppb)

Ag 328.068 Axial 0.88Al 308.215 Radial 22As 189.042 Axial 1.6Ba 455.403 Radial 0.39Be 313.107 Radial 0.29Ca 315.887 Radial 6.6Cd 214.438 Axial 0.051Co 228.616 Axial 0.26Cr 267.716 Axial 0.39Cu 324.754 Axial 0.45Fe 271.441 Radial 73K 766.490 Radial 40Mg 279.079 Radial 37Mn 260.569 Axial 0.17Na 589.592 Radial 9.3Ni 231.604 Axial 0.31Pb 220.353 Axial 0.76Sb 206.833 Axial 1.2Se 196.090 Axial 1.9Tl 190.856 Axial 0.66V 292.402 Axial 0.39Zn 206.200 Axial 0.20

Table 4: Method Detection Limits

Quality Control ProcedureMethod 6010b requires that a very strict quality controlprocedure should be followed to ensure the validity ofsample data. Quality control checks are carried outfollowing instrument calibration, during sample analysisand at the end of the analytical run. All checks must meetthe required criteria for the sample data to be acceptable.

The instrument was set up using the parametersshown in Table 1 and allowed to stabilize for 30 minutesprior to calibration.

Immediately after calibration, an Initial CalibrationVerification (ICV) solution, calibration blank andContinuing Calibration Verification (CCV) solution wererun. The calibration blank readback must be within 3times the method detection limit for each element, whilethe calibration verification solutions must be within 10 %of the actual values. The standard deviation of a minimumof 2 re-samples of each verification solution must be lessthan 5 % for the data to be acceptable.

Analysis of the CCV solution and calibration blankwas then repeated every 10 samples to ensure theinstrument remained in calibration, the results for the firstCCV are shown in table 5.

Element Initial Cal Check Continuing Cal Check (ICV) (mg/L) (CCV) (mg/L)

Actual Measured Actual Measured

Ag 0.5 0.495 1 0.998Al 2.5 2.553 25 25.520As 1.0 1.019 5 5.190Ba 0.5 0.490 5 4.862Be 0.5 0.481 2.5 2.410Ca 10.0 10.140 25 25.100Cd 0.5 0.510 5 4.985Co 0.5 0.502 5 4.909Cr 0.5 0.46 5 4.849Cu 0.5 0.488 5 4.951Fe 5.0 5.060 25 24.870K 10.0 9.935 25 25.220Mg 6.0 6.014 25 25.120Mn 0.5 0.494 5 4.855Na 10.0 10.000 25 25.300Ni 0.5 0.501 5 4.902Pb 1.0 1.006 5 4.895Sb 1.0 1.000 5 9.933Se 1.0 1.008 10 10.020Tl 1.0 1.028 10 9.566V 0.5 0.500 5 4.909Zn 1.0 1.020 5 4.954

Table 5: Calibration Checks

The iCAP 6000 Series ICP features a highly regulatedtemperature control system. This temperature controlensures that the spectrum position remains constant andpeak analytical performance is maintained over extendedtime periods even with fluctuations in the laboratoryconditions. This ensures that the long-term signal stabilityof the instrument is exceptional and that CCV samples arewithin acceptable levels for extended periods, resulting infewer sample re-runs.

Interference check solutions were run prior to the startof the sample analysis to verify the accuracy of the inter-element corrections factors and background correctionpoints. Interference Check Sample A (ICSA) was preparedcontaining 250 mg/L each of Al, Ca, Mg and 100 mg/LFe. Interference Check Solution AB (ICSAB) was thenprepared by spiking the ICSA solution with concentrationsof 0.05 to 1 mg/L for the analyte elements. The valuesmeasured for ICSAB must be within 20 % of the truevalue for the data to be acceptable.

Data is shown in Table 6 below.

Element ICSA ICSAB Target Value % Recoverymg/L (mg/L) (mg/L) (mg/L)

Ag <LOD 0.212 0.210 101.0As 0.003 0.112 0.097 115.5Ba 0.002 0.499 0.475 105.1Be <LOD 0.482 0.482 100Cd 0.001 1.052 0.916 114.8Co 0.003 0.509 0.455 111.9Cr 0.040 0.516 0.506 102.0Cu 0.017 0.532 0.537 99.1Mn 0.016 0.494 0.483 102.3Ni 0.013 1.037 0.930 111.5Pb 0.005 0.059 0.051 115.7Sb 0.004 0.667 0.585 114.0 Se 0.004 0.060 0.051 117.6 Tl 0.001 0.096 0.096 100.0 V 0.005 0.500 0.481 104.0 Zn 0.045 1.060 0.975 108.7

Table 6: Interference Checks

Internal laboratory quality control checksMethod performance was verified with two differentLaboratory Control Samples, a water (LCSW) and a soildigest (LCSS). The results of this are shown in table 7.The water digest was prepared by the addition of nitricacid to the sample so that the final concentration of nitricacid in the sample was 10 %. The soil digest was preparedby digesting 1 gram of sample in a mixture of nitric andhydrochloric acid and diluting the sample so the finalconcentration of acid was 5 % nitric acid and 1 %hydrochloric acid.

Element LCSS LCSW

Measured Target Measured Targetppm ppm ppm ppm

Ag 0.0223 0.0209 0.479 0.495Al 0.2722 0.3090 2.600 2.482As 1.1750 0.9300 1.019 0.996Ba 0.0053 [0.0053] 0.491 0.502Be 0.0183 0.0188 0.477 0.493Ca 175.2000 184.0005 10.410 10.180Cd 0.0448 0.0416 0.521 0.494Co 0.1565 0.1400 0.523 0.496Cr 0.0982 0.0965 0.495 0.490Cu 6.7470 6.6800 0.499 0.490Fe 21.4300 21.0000 5.083 5.107K 0.0579 [0.1024] 9.924 10.008Mg 112.1000 113.0000 6.091 6.003Mn 0.1996 0.2010 0.500 0.495Na 0.0536 [0.0928] 10.160 10.039Ni 0.0622 0.0568 0.518 0.492Pb 0.2655 0.2240 1.039 0.996Sb 0.2702 0.2130 1.006 0.992Se 0.0473 0.0370 0.942 1.005Tl 0.0361 0.0381 1.044 1.027V 0.0679 0.0658 0.510 0.501Zn 0.1751 0.1750 1.071 1.000

Table 7: Internal laboratory control checks

ConclusionsThe Thermo Scientific iCAP 6500 Duo far exceeds therequirements needed to meet EPA 6010 protocols.

The instrument has a high resolution optical systemwhich minimizes spectral interferences and reduces straylight. It uses the latest generation design of our uniqueCharged Injection Device detector which offers highersensitivity and lower noise, resulting in better signal tobackground ratios.

The integrated structural castings and precision regulatedoptics ensure excellent long term stability.

The results of these developments are an instrumentthat has exceptional stability and detection limit performancewhich meet and exceed the requirements for this type ofanalysis.

ReferencesUSEPA SW-846 Method 3050b, Revision 2, December 1996.

USEPA SW-846 Method 6010b, Revision 2, December 1996.

USEPA SW-846 Method 6010c, Revision 3, November 2000.

AN40836_E 07/07C

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