Problems with Arsenic Detection: Problems with Arsenic Detection: When NIOSH and EPA Methods FailWhen NIOSH and EPA Methods Fail

Karen Gunderson, MPH, CIHKaren Gunderson, MPH, CIHJDSUJDSU

May 17, 2006May 17, 2006

OverviewOverviewIntroduction to use of polishing rougeIntroduction to use of polishing rouge

Analytical results and regulatory Analytical results and regulatory compliance issuescompliance issues

Interferences identifiedInterferences identified

Determining true concentration of arsenic Determining true concentration of arsenic

Use of Rouge Polishing CompoundUse of Rouge Polishing Compound

Prior to coating, glass is washed in a flat plate washer, Prior to coating, glass is washed in a flat plate washer, using a mixture of soap, water, and rouge.using a mixture of soap, water, and rouge.

Manufacture of RougeManufacture of Rouge

Mined in Southern Mined in Southern California by California by MolycorpMolycorp

Processed by WR Processed by WR GraceGrace

Sold by distributor Sold by distributor Universal PhotonicsUniversal Photonics

Rouge Ingredients Listed on MSDSRouge Ingredients Listed on MSDS

8080--90% rare earth oxides 90% rare earth oxides (60% is cerium oxide)(60% is cerium oxide)

33--6% amorphous silica6% amorphous silica

0.10.1--0.2% thorium oxide 0.2% thorium oxide

Rare Earths on Periodic TableRare Earths on Periodic Table

Rare earths are in greenRare earths are in green

Rouge is Prepared from Rouge is Prepared from BastasiteBastasite: : A Mixture of Rare EarthsA Mixture of Rare Earths

50% Cerium Oxide (CeO2)50% Cerium Oxide (CeO2)30% Lanthanum Oxide (La2O3)30% Lanthanum Oxide (La2O3)1313--14% Neodymium Oxide14% Neodymium Oxide4% Praseodymium4% Praseodymium0.5% Samarium0.5% Samarium0.2% Gadolinium0.2% Gadolinium0.1% Europium0.1% Europium0.15% Thorium Oxide0.15% Thorium Oxide0.022% Lead oxide0.022% Lead oxideTrace of Terbium and HolmiumTrace of Terbium and Holmium

Analytical Results and Analytical Results and Compliance IssuesCompliance Issues

…….where the problems began .where the problems began

DefinitionsDefinitionsICP/AESICP/AES

Inductively Coupled Plasma with Atomic Inductively Coupled Plasma with Atomic Emission Spectroscopy Emission Spectroscopy

ICP/MSICP/MSInductively Coupled Plasma with Mass Inductively Coupled Plasma with Mass SpectrometrySpectrometry

AAAAAtomic AbsorptionAtomic Absorption

Gas FurnaceGas FurnaceHydrideHydride

Discharge Water Samples with Discharge Water Samples with Unexpected Arsenic HitsUnexpected Arsenic Hits

City of Santa Rosa Arsenic Discharge Limit City of Santa Rosa Arsenic Discharge Limit = = 0.47 mg/L 0.47 mg/L

Arsenic Concentration

Water Samples 2/8/2005 (mg/L)

Water Samples 2/9/2005 (mg/L)

Sequoia-City (ICP/AES) 1.2 0.52 Sequoia-JDSU (ICP/AES) 0.99 0.13 City Lab (ICP/MS) 0.028 0.019

Huge Discrepancies in Huge Discrepancies in Arsenic Levels of Bulk SamplesArsenic Levels of Bulk Samples

Comparison of Arsenic Analyses of Solid Rouge Datachem Alpha Sequoia K-Prime

Sample Description

ICP-AES (mg/kg)

EPA 3050B/ EPA 6010B

Furnace AA (mg/kg)

EPA 3051/ EPA 7060

ICP-AES2 (mg/kg)

EPA 3050B/ EPA 6010B

ICP-MS (mg/kg)

EPA 3050/ EPA 6020

Composite Flatplate ResidueM 3300 < 5 -- -- Composite Flatplate ResidueC 3300 < 5 -- -- (Rouge) Raw Material Rareox 14 ST, Lot 102 3700 < 5 7500 110 ICP/AES1 LOD 500 mg/kg under the method of standard additions ICP/AES2 LOD 2 mg/kg ICP-MS LOD 2.5 mg/kg Furnace AA LOD 5 mg/kg

Slide from Slide from DatachemDatachem line 189 line 189 ICP/AESICP/AES

Rouge

Arsenic Standard

Concerns about Employee Concerns about Employee Exposure to Polishing Rouge Exposure to Polishing Rouge

Loading the rouge into the flat plate washerLoading the rouge into the flat plate washer

Exposures During MaintenanceExposures During Maintenance

Preventative Maintenance on the Preventative Maintenance on the Flat Plate WasherFlat Plate Washer

Personal Air SamplesPersonal Air SamplesAnalyzed for Arsenic by NIOSH 7300 (ICP/AES)Analyzed for Arsenic by NIOSH 7300 (ICP/AES)

21%21%0.0021mg/m0.0021mg/m330.004 mg/m0.004 mg/m33250 min250 minMaintenance Maintenance Worker #1Worker #1

47%47%0.0047 mg/m0.0047 mg/m330.009 mg/m0.009 mg/m33252 min252 minMaintenance Maintenance Worker #1Worker #1

% PEL% PEL8 hour TWA8 hour TWAConcentrationConcentrationTimeTimeSampleSample

CalCal--OSHA PEL is 0.01 mg/mOSHA PEL is 0.01 mg/m33

Arsenic is regulated as a carcinogen (8CCR4214) with Arsenic is regulated as a carcinogen (8CCR4214) with an action level of 0.005 mg/m3an action level of 0.005 mg/m3

Investigation initiated to resolve Investigation initiated to resolve problems with conflicting dataproblems with conflicting data

Why do the arsenic levels detected vary over 3 Why do the arsenic levels detected vary over 3 orders of magnitude?orders of magnitude?

Labs stand behind their resultsLabs stand behind their results

Manufacturer claims there is no arsenic in the Manufacturer claims there is no arsenic in the rougerouge

Manufacturer explains that:Manufacturer explains that:Rare earths interfere at arsenic line when using ICP Rare earths interfere at arsenic line when using ICP methods methods –– ““ignore ICP resultsignore ICP results””

““Gas furnace AA is the best techniqueGas furnace AA is the best technique””

Manufacturer provided data that showed Manufacturer provided data that showed how rare earths could interfere at the how rare earths could interfere at the arsenic linearsenic line

ICP/AES at line 189ICP/AES at line 189ICP/MS at line 75ICP/MS at line 75

ICP/AES Interference at line 189ICP/AES Interference at line 189

La 1000 ppm

As 5 ppm

Pr 1000ppm

Sm 1000ppm

Nd 1000ppm Ce 1000ppm

5.64% of Neodymium isotopes 5.64% of Neodymium isotopes are mass of 150are mass of 150NdNd 150 ionizes to 2+ in ICP150 ionizes to 2+ in ICP(mass/charge ratio = 75)(mass/charge ratio = 75)

7.4% of Samarium isotopes are 7.4% of Samarium isotopes are mass of 150mass of 150SmSm 150 ionizes to 2+ in ICP150 ionizes to 2+ in ICP(mass/charge ratio = 75)(mass/charge ratio = 75)

In a mass spectrometer, both In a mass spectrometer, both are seen on line 75 and could are seen on line 75 and could be interpreted to be Asbe interpreted to be As

100% of As 100% of As isotopes have isotopes have mass of 75mass of 75

Mass Mass SpectrometrySpectrometry

10 10 ppmppmNeodymium High Neodymium High Purity StandardPurity Standard

ICP MS Spectra at ICP MS Spectra at Line 75Line 75

10 10 ppmppmSamarium High Samarium High Purity StandardPurity Standard

ICP MS Spectrum at ICP MS Spectrum at Line 75Line 75

Testing for rare earth interferencesTesting for rare earth interferences

High purity water samples spiked with rare earth High purity water samples spiked with rare earth elements suspected of causing interferences elements suspected of causing interferences were preparedwere prepared

Analyzed for arsenic by the same labs as the Analyzed for arsenic by the same labs as the water and bulk sampleswater and bulk samples

In addition, the AA method was tested by In addition, the AA method was tested by submitting a solid rouge sample spiked with submitting a solid rouge sample spiked with arsenic (380 arsenic (380 ppmppm AsAs22OO33).).

Rare Earth Spike ResultsRare Earth Spike Results

Laboratory Analytical Method

Spike (Type and

Concentration)

Result as Arsenic (ppm)

Datachem ICP/AES Praseodymium 1000ppm in water < 0.5

“ “ Lanthanum 1000 ppm in water 49

“ “ Cerium 1000 ppm in water < 0.5

K-Prime ICP/MS Neodymium 1000 ppm in water 7.3

: “ Samarium 1000 ppm in water

Cannot be determined due to interferences

Alpha Analytical Gas Furnace AA

Arsenic 380 ppm in Rareox 14 Lot 102 (as As2O3)

< 5.0

Laboratory Analytical Method

Spike (Type and Concentration)

Result as Arsenic (ppm)

Datachem ICP/AES Praseodymium 1000ppm in water < 0.5

“ “ Lanthanum 1000 ppm in water 49

“ “ Cerium 1000 ppm in water < 0.5

K-Prime ICP/MS Neodymium 1000 ppm in water 7.3

: “ Samarium 1000 ppm in water

Cannot be determined due to interferences

Alpha Analytical Gas Furnace AA

Arsenic 380 ppm in Rareox 14 Lot 102 (as As2O3)

< 5.0

Problem not yet solved..more ?sProblem not yet solved..more ?s

Arsenic detected in ICP methods was not Arsenic detected in ICP methods was not in a 1in a 1--1 correspondence with the 1 correspondence with the concentration of rare earthconcentration of rare earth

e.g. 1000ppm La e.g. 1000ppm La 49 49 ppmppm AsAsSome of the arsenic detected could be due to Some of the arsenic detected could be due to interference, but some could be real.interference, but some could be real.

Why didnWhy didn’’t the AA method work on the t the AA method work on the spiked sample?spiked sample?

Why was the AA nonWhy was the AA non--detect?detect?

Manufacturer chemist claims insoluble arsenate Manufacturer chemist claims insoluble arsenate formed in the presence of nitric acidformed in the presence of nitric acid

CeCe4+4+ in rouge oxidizes Asin rouge oxidizes As3+3+ to Asto As5+5+, creating , creating (AsO(AsO44))33--

(AsO(AsO44))33-- reacts with Lareacts with La3+3+, creating an insoluble , creating an insoluble compound lanthanum arsenate, LaAsOcompound lanthanum arsenate, LaAsO44..

How much arsenic is in the rouge?How much arsenic is in the rouge?Many techniques were investigated and Many techniques were investigated and abandoned:abandoned:

Run rouge slurry into an AARun rouge slurry into an AAWould require method development ($2,000 per day Would require method development ($2,000 per day --not good for air or water samplesnot good for air or water samples

XRFXRFProton Induced XProton Induced X--Ray Analysis (PIXE)Ray Analysis (PIXE)Hydride Generation Atomic FluorescenceHydride Generation Atomic Fluorescence

Detection limit too high 100 Detection limit too high 100 -- 1000 1000 ppmppm, due to rare , due to rare earth matrixearth matrix

More techniques investigatedMore techniques investigatedGlow Discharge Mass SpectrometryGlow Discharge Mass Spectrometry

National Research Council in CanadaNational Research Council in Canada-- Measures Measures one particle at a time; our sample is not one particle at a time; our sample is not homogenoushomogenous

Neutron ActivationNeutron ActivationUniversity of Missouri, lanthanides give many University of Missouri, lanthanides give many spectral lines but arsenic only 4 spectral lines but arsenic only 4 –– difficult to difficult to determinedetermine

ICP/MS with oxygen reaction cell at research ICP/MS with oxygen reaction cell at research lablab

Too expensive, $2,000 per day at private labToo expensive, $2,000 per day at private lab

ICP/MS Oxygen Reaction Cell at ICP/MS Oxygen Reaction Cell at MolycorpMolycorp LaboratoryLaboratory

Used Used perchloricperchloric acid digestacid digestLooked at Looked at AsOAsO at Line 91 on Mass Specat Line 91 on Mass SpecVarying ResultsVarying Results

Matrix blank higher than sampleMatrix blank higher than samplePoor recoveriesPoor recoveriesSample results vary over one order of Sample results vary over one order of magnitude (7magnitude (7--76ppm As)76ppm As)Attributed to zirconium interferenceAttributed to zirconium interference

ZrOZrO balls used to process rougeballs used to process rouge

WhatWhat’’s Next?s Next?

Digest with Digest with perchloricperchloric at lower temperature at lower temperature in in teflonteflon beakers (<220beakers (<220°°C)C)Form EDTA anionic complexes with rare Form EDTA anionic complexes with rare earthsearthsSeparate out anionic complexes on a Separate out anionic complexes on a chromatographchromatographRun through Mass Spectrometer and look Run through Mass Spectrometer and look at line 75 for arsenicat line 75 for arsenic

SummarySummaryArsenic detection is difficult with ICP, AA, and other Arsenic detection is difficult with ICP, AA, and other methods in the presence of rare earths (lanthanides).methods in the presence of rare earths (lanthanides).

ICP/AES detects lanthanum as arsenic.ICP/AES detects lanthanum as arsenic.

ICP/MS detects neodymium and samarium as arsenic.ICP/MS detects neodymium and samarium as arsenic.

The AA can not detect arsenic in the presence of rare The AA can not detect arsenic in the presence of rare earths, possibly due to a reaction in the acid digest.earths, possibly due to a reaction in the acid digest.

No reliable method has been found to quantify No reliable method has been found to quantify arsenic in this rare earth oxide matrixarsenic in this rare earth oxide matrix

AcknowledgementsAcknowledgements

Thank you to the following people for their Thank you to the following people for their assistance with the investigation:assistance with the investigation:

Carole Thoraval, PhD, JDSUCarole Thoraval, PhD, JDSUEd McNew, MS, Ed McNew, MS, MolycorpMolycorpMark Mark HrezdakHrezdak, Universal Photonics, Universal Photonics

Any suggestions for lab techniquesAny suggestions for lab techniques……karenkaren..gundersongunderson@@jdsujdsu.com.com