N<< d 0 0 0 0 3 5

To: Jay Thakkar / _ ,j cc: Rich Boice

Troa: Duane Kruse

Re: Evaluation of the arsenic data for MIDCO I and II

The MIDCO I and II sites include slag and other wastes from asecondary aluminum smelter. This site has produced soil samplescontaining aluminum concentrations as large as 140000 mg/kg. RichBoice has performed a graphical analysis that shows the arsenicdata increasing proportionally with the aluminum results. Fromthis Rich inferred that a positive interference from the aluminumis affecting all arsenic results.

Some of the data packages from the site were reviewed foradditional evidence of interference. This review indicated thatthe arsenic results were obtained by graphite furnace AAS using adeuterium (D2) lamp background correction system. An inspectionof the raw data shows many of the matrix spikes and analyticalspikes are out of control. Printouts of the atomization peaks forsome samples showed very high levels of background and in somecases, negative peaks for the atomic signal. All of this evidencesuggests that significant interferences exist for the arsenicresults.

An inspection of reference emission lines in "ICP-Atomic EmissionSpectroscopy" by Fassel shows that an aluminum line coincides withthe arsenic analytical line at 193.7 nm. Based on the level ofaluminum found at this site, aluminum is the major (but not theonly) contributor to the arsenic interference.

The "Graphite Furnace AAS, A Source Book" by Walter Slavin alsoindicates that aluminum is an interferant for arsenic. Severalsources reported that aluminum levels above 100 mg/1 are notcorrectable without the use of zeeman background correction. Otherinterferants mentioned were phosphate, sulfate, sodium, potassiumand refractory materials. All of these are potentiallyuncorrectable by D2.

As mentioned above, aluminum concentrations above 100 mg/1 areuncorrectable. For this case that concentration is approximately10000 mg/kg Al. Thirteen of the MIDCO II phase 1 results attachedto this report contain aluminum in amounts exceeding this level.The arsenic results for these samples should be consideredunusable.

Fich Boice asked if a correction factor could _ ._ w u u ^the aluminum interference from the arsenic results based onrelative strengths of the emissions reported by

REMEDIAL ̂ENFORCEMENT

RESPONSE BRANCH

this alone, dividing the aluminum concentration by 50 will give theequivalent concentration of arsenic. Caution should be usedregarding this correction factor. This factor is derived from datafor aluminum and arsenic obtained by ICP. The arsenic results forthis case were obtained by GFAA which is much more sensitive thanICP. Because of the differences in sensitivity for the twoinstruments, the use of the ICP aluminum result to correct forinterference in the GFAA arsenic result may be very misleading.Also as previously mentioned, sodium and potassium interfere witharsenic and were also present in concentrations similar toaluminum. The sodium and potassium interferences are enhanced bysulfate which was not assayed for these samples. Even if thealuminum interference could be mathematically corrected, thearsenic results could still be affected by these and otherinterferences. Another factor to consider is that the mathematicalrelationship of any interfering element with arsenic may not belinear.

Another danger in trying to correct for aluminum interference isthat other instrumental factors may have an influence on thealuminum/arsenic interference. The influence of the other factorscannot be accessed from the raw data. These factors include butmay not be limited to the following: the ages of the D2 lamp andthe arsenic lamp, slit width, condition of the graphite tube, andthe type and amount of matrix modifier used.

There are many factors beyond aluminum that can have an affect onthe arsenic. It is my professional judgement that the use of a anymathematical correction for the aluminum interference on arsenicwould be ill advised without serious consideration of the otherfactors that have been mentioned in this memo.

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•' ~'

GRAPHITE FURNACE AASA SOURCE BOOK

Walter Slavin

The Perkin-Elmer Corporation, Norwalk, CT 06856Printed in the United States of America

Order Number: 0993-8139

,d sample preparation.-ials for Al is usually done by-enerally high. However Car-s methods and chose furnace.ten, waste waters, sewage

ite Al in seawater was studied4 from 0.1 /*g/L near the sur-n and to 0.3 j*g/L at 400 m. Aling the STPF technology (534).in metallurgical samples.* -72, determined Al in iron

1% Fe, they could not dis-mt&ining no Al. With theCl the signals were the sameI to dissolve steel, no problemn of Al, Persson et al. (678),d Al in steels. They elimi-Al by adding ammoniumtdards, thus making it possi-other steel constituents didLivity./zed for AI using furnace: in siHcon materialssed the method of additionslure when the solutions wereak absorbance signals wereaphite tubes in the

that Co and Fe interferesing a spectral slit width ofing line within the spectral•ference was not present

rials including blood from•s by Ward et ai (951). TheyC and atomization atgluconate binding of the Sb.ng as a matrix modifier. Sb,iith and Griffiths (795)9 of N2 and H2 as the sheath

gas. They compared two methods, one was an extraction of themetals into MIBK with APDC and a second was preceded by wetoxidation prior to extraction. Interferences kept them from using adirect method and they claim that the CI of Sb is very volatile. Theyused 1 to 3% acetic acid to stabilize the urine, otherwise heavymetals were carried down with the CaPO< precipitate. HN03 causedserious interference for Sb. They found that the levels of Sb in 18unexposed people was generally below 1 pg/L.

Haynes (329) studied the Sb determination in municipal solidwastes, thus both organic and inorganic materials, using the HGA-2100. He added Ni(NO,)j and MgfNOjfe as an established ashingaid. Using radio Sb as a tracer, he found that external ashing ofcombustible materials for 4 hours at 450°C provided Sb recoveriesof 95%. In his furnace method he charred at 800°C without loss ofSb. He got good agreement for Sb with other labs for NBS fly ash.coal and orchard leaves.

Sb(III> and (V) were separated by extraction into APDC-MIBK(860) and there is some discussion in "Arsenic". A very good paperwas published by Han-wen et al. (323) describing the separatedetermination of Sb(III) and Sb(V) at very low levels in environ-mental waters. They state the European Community Standard as 10pg'L maximum permissable level for Sb in drinking water. Theyextracted the Sb(III) in n-benzyl-n-phenylhydroxylamine and CHC13in a 25-fold volume ratio with the water sample. The 20-pL CHC13sample provided a characteristic concentration of 0.04 ^g/L whichcalculates to a characteristic mass of 20 pg/0.0044 A. in excellentagreement with the aqueous sensitivity (782) of the HGA-72 furnacewhich they used Cu was found to be preferable to Ni or Pt as amatrix modifier for Sb, and an aqueous solution of Cu was separ-ately deposited in the furnace tube. No interferences were found forother materials present in environmental samples but the additionof tartaric acid was necessary to preserve the StKHI) in the samples.

ArsenicThe various analytical techniques used for the determination of

As were recently very well reviewed by Brooks ft ai (82). Of the 363papers published on the subject over the past 4 years, 31% usedAAS. 22% neutron activation, 16% molecular absorption spectropho-tometry, 11% AES, 10% electrochemistry, and 7% x-ray. They dis-cuss separation and extraction techniques. The furnace is shown tobe the most sensitive and generally useful technique for As. Theyrecommend the absorption of arsine in a silver solution followed byfurnace AAS for very high sensitivity. They list the several claims

if

of furnace A AS interferences and A AS applications.The atom formation process for As was studied by Akman et al.

(7). They used a combination of Arrhenius plots and observation ofthe experimental parameters of the HGA-76 furnace. Their appear-ance temperature is 1300°C. As is converted to As203on the gra-phite and vaporizes to AsO. It is dissociated, probably directly to Asin the vapor. By showing that char losses increase with the length ofthe char step at temperatures above 450°C, they suggest that somegaseous AsO is lost by convection and diffusion. They provide theoryand data for As using the hydride technique.

In his review, Matousek (554) stated that the As sensitivity islower on pyrolytic graphite than on ordinary graphite and thatthere is an aging effect on pyrolytic graphite. This is not consistentwith our experience.

In the original matrix modifier paper, Ediger (192) used Ni forAs and most workers since have found the addition of Ni an impor-tant part of the As determination. Xiao-quan et al. (975a) haverecommended that Pd is superior to Ni. Since peak A was the criter-ion, the Pd apparently made the peaks more narrow and, therefore,higher. However, the maximum char temperature was about thesame for Pd. Mo and Ni. Much lower char temperatures were foundwith Zr and Ba. Peak area measurements would probably haveshown the Pd, Ni and Mo modifiers to be very similar.

Riley (724) reported that Al above 100 mg/L provided an uncor-rectable spectral interference in the determination of As at the193.7 nm As line. There was no problem at the 197.2 nm As line,although this line is less sensitive. Pruzkowska et at (702) confirmedtheir observation and found that Zeeman background correctionlargely removed the Al interference at the more sensitive line of As.Fernandez and Giddings (234) showed that phosphate, as Pg, selec-tively absorbed the background radiation at the As line and createdan interference which was not present when Zeeman backgroundcorrection was used.

As was determined in vegetable products by Hoenig et al. (347a,348) using an IL 655 furnace. P interfered very strongly, probablybecause of the structured background as reported by Fernandez andGiddings (234), an interference which is removed by Zeeman back-ground correction. There seemed to be little effect of K, Ca or Mg.They were forced to extraction of the As prior to furnace determina-tion. Puttemans et ai (704a) developed extraction methods for As inbiological materials to avoid interferences.

The optimum conditions for the determination of As in environ-mental waters was studied by Chakraborti et al (118) using the

HGA-74. Even with thecorrection, interferencesforced the authon to de\only uncoated tubes. Theabout 0.5 MHNO,. Theincreased the Na and K iHN03 destroyed the tubealso had trouble determistudy for 9 elements. OnAs in such samples.

The determination tfj!important in connection *methods since As will poiproblems, focusing especupon the organic bondingthe wall and with peak mlprovided troubles becaua

As was determined in rusing the HGA-2100. addan ashing aid. Using radi98%. He charred at 1200°<values for fly ash, coal amused Pd as a matrix modifor fly ash and biological Aable to determine As in sl\interference. They chose t

Another environmentalfrom the vaporized toxic rEbdon and Pearce (190) &in coal slurries. For some;materials be used as standmatrix modifier. Their pyrthan ordinary graphite talgraphite was used for the i

The interferences in theticulates were studied by V2100 furnace. They found jand recommended workingNa and Ni salts in HC1 andfor an As test solution. Mgresults from varying concewell when atomization is atat 2300°C. Atmospheric pa:

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\S applications.was studied by Akman et a!.enius plots and observation of4GA-76 furnace. Their appear-nverted to As20s on the gra-xiiated, probably directly to Assses increase with the length of150°C, they suggest that somei diffusion. They provide theoryhnique.d that the As sensitivity is

inary graphite and that"riphite. This is not consistent

-er, Ediger (192) used Ni fori the addition of Ni an impor-io-quan et al. (975a) have-"i. Since peak A was the criter-5 more narrow and, therefore,temperature was about the:har temperatures were foundents would probably havebe very similar.X) mg/L provided an uncor-?termination of As at them at the 197.2 nm As line.zkowska et al. (702» confirmedan background correction

' e more sensitive line of As.--^iat phosphate, as Pg, selec-ion at the As line and createdwhen Zeeman background

iucts by Hoenig et al <347a.red very strongly, probablyis reported by Fernandez ands removed by Zeeman back-little effect of K, Ca or Mg.s prior to furnace determina-ex tract ion methods for As inces.mination of As in environ-orti ft al. (118) using the

HGA-74. Even with the addition of Ni and the use of backgroundcorrection, interferences from Al at ppm levels, and from K and Na,forced the authors to develop an extraction procedure. They usedonly uncoated tubes. They preferred to add 100 mg/L Ni(N03>2 inabout 0.5 M HN08. The presence of high concentrations of sulfateincreased the Na and K interferences. Use of J g/L Ni in 0.1 MHN03 destroyed the tubes in less than 25 firings. Wageman (944)also had trouble determining As in river water in an interlaboratorystudy for 9 elements. On the other hand, we (533) had no trouble forAs in such samples.

The determination of As in shale oils and shale oil waters isimportant in connection with the development of oil extractionmethods since As will poison the catalysts. Fabec (211»studied suchproblems, focusing especially on variations in As signals dependingupon the organic bonding of the As. He used the HGA-500 but fromthe wall and with peak absorbance signals. Use of uncoated tubesprovided troubles because of the porosity of the graphite.

As was determined in municipal solid wastes by Haynes (329)using the HGA-2100, adding NKNO^ and Mg(N03)2, the latter asan ashing aid. Using radio As as a tracer, the As recoveries were98%. He charred at 1200°C. He got good agreement with NBSvalues for fly ash, coal and orchard leaves. Xiao-quan et al. (975a)used Pd as a matrix modifier with wall and peak A measurementsfor fly ash and biological As samples. Kempton ft al (4091 were notable to determine As in sludges correctly because there was aninterference. They chose to use a hydride method.

Another environmental problem arises with atmospheric pollutionfrom the vaporized toxic metal impurities when coal is burned.Ebdon and Pearce (190) determined As in acid solutions of coal andin coal slurries. For some samples they required that similar coalmaterials be used as standards. They added Ni and Mg(NOs)2 as amatrix modifier. Their pyrolytic graphite tubes gave broader peaksthan ordinary graphite tubes, indicating that a poor grade ofgraphite was used for the pyrolytically coated tubes.

The interferences in the determination of As in atmospheric par-ticulates were studied by Walsh ft al. (950). They used the HGA-2100 furnace. They found greatly reduced signals in HC1 and HFand recommended working in HN03. Many Ca, Cu, Fe. K. Mn. Mg.Na and Ni salts in HC1 and HgSC^ provided variable absorbancesfor an As test solution. Mg is shown to reduce otherwise variableresults from varying concentrations of Na and S04. Ni works aswell when atomization is at 2500°C, but the Mg permits atomizationat 2300°C. Atmospheric particulates were analyzed for As also by

Ht.

r 'I

Bernard and Pinta (57) using the HGA-500 and HGA-72. Pyrolyticand ordinary graphite provided the same results although the slopeof the curve reduced as the tube aged.

As has proven particularly difficult to determine in matrices thathave large amounts of refractory or inorganic materials. Prusz-kowska and Barrett(702) have therefore used the STPF techniqueto determine traces of As, and Se, in rock materials. They confirmedthat A) produced uncorrectable background interference at the194-nm As line using continuum background correction and that theZeeman corrector had little problem in these conditions. Neverthe-less they used the 197-nm line which tolerated about 9 us of Al onthe platform using Zeeman background correction. The backgroundabsorbance at 197 nm for 9 M£ of Al on the platform exceeded 2 A.They dissolved 0.5 g of rock in HF and HC104 and evaporated thesolution to dryness. The process was repeated several times and theresidue was taken up finally in 100 mL of 1% HN03. Some Ca andAl fluorides remained as an insoluble residue, but the trace metalswere quantitatively leached from the sample. Ni, 20 M£ on the plat-form, was used as a matrix modifier. The STPF determination wasquantitated against a standard curve in the same matrix modifier.The characteristic mass was 33 pg/0.0044 A-s at the 197-nm line andthe detection limit was 0.3 ^g/g in the rock. The agreement withrecommended values for 5 rock standards from the U.S. GeologicalSurvey was very good. Xiao-quan ft al, (975a) used their Pd modi-fier for soil samples for the As determination.

There is considerable interest in As speciation. As(UI) was separ-ated from As(V) by extraction into APDC in MIBK prior to furnaceanalysis by Subramanian and Meranger (860). In a subsequentarticle they (859) reported a comparison of their method for totaland speciated As with anodic stripping vol tarn me try for pollutedwater. Their arrangement permitted the two valence states of Sband Se also to be separated. Optimum conditions are reported. Theauthors felt the extraction also avoided furnace interferences. Theyused the HGA-2100 and N2 as a purge gas. Puttemans and Massart(704) also separated Asdll) from As<V) by extraction. Asdlll isextracted into APDC from an acid medium. To measure As(V). firstthe As(III) is measured, then the As (V) is reduced and As is againextracted for the sum of As(III) and As<V). Pacey and Ford (655)also separated the As species, As(III), As<V), monom ethyl arsenicacid and dimethylarsenic acid by ion-exchange chromatography.The separated fractions were analyzed, off line, by furnace AAS.Persson and Irgum (675) determined sub-ppb dimethylarsinic acidin sea water by extraction on ion exchange columns which did not

retain inorganic As. The ABrinckman et al (78a, 66

tor to study speciation of orcompared a conventional ftAs compounds. They founddepending upon the componique will remove the matrof the calibration.

Woolson ft ai (973) separAs compounds by using a c2100 furnace. A bar graphresulted.

BariumFrom data derived from

daev and Bukraev (610) belmation from the graphite. 1believed that Ba proceededciation of the oxide to solid

Barium is an interestinghaps, slightly more sensitivtion. It requires a high tern]ally recommended from theplatform (780j). In early wovery much more sensitive tilined with Ta foil as eompaiat that time. Probably newas vaporization from aTaVrequires a high temperatunFernandez and lannaroneC50%. Their improvement forite is almost 15-fold. Becau*ture and the resonance line;determination benefits fromthe continuum radiation fro:bright or the determinationbright and the wavelength i:rector is not useful at the Bathat use a tungsten-iodine lalong wavelength determinatdetermination. The Zeemanticularly useful for Ba,

HGA-600 and HGA-72. Pyrolytic•» same results although the slope

cult tt> determine in matrices thator inorganic materials. Prusz-erefore used theSTPF techniquein rock materials. They confirmedickground interference at thelackground correction and that the»m in these conditions. Neverthe-ch tolerated about 9 /iff of A) onround correction. The backgroundVI on the platform exceeded 2 A.and HC)04 and evaporated the

repeated several times and the. fflL of 1% HNOj Some Ca andble residue, but the trace metalsJie sample. Ni, 20 »g on the plat-er. The STPF determination was•ve in the same matrix modifier.'0.0044 A -s at the 197-nm line andthe rock. The agreement with.ndards from the U.S. Geological•i al (975a) used their Pd modi-•r mi nation.As speciation. As<III) was separ-APDC in MIBK prior to furnaceanger (860). In a subsequentj-i&on of their method for totalping voltammetry for pollutedad the two valence states of Sb

~n conditions are reported. The^_jd furnace interferences. They•ge gas. Pu tie mans and M assart4V) by extraction. AsdH) ismedium. To measure As(V), firsta (V) is reduced and As is again1 Aa(V). Pacey and Ford (655)I), Ag(V), monomethylarsenicn-exchange chromatography,zed, off line, by furnace AAS.•d sub-ppb dimethylarsinic acid:hange columns which did not

retain inorganic As. The As was determined in the HGA-74.Brinckman ft aL (78a. 665) used GFAAS as a metal-specific detec-

tor to study speciation of organometallic compounds. In (78a) theycompared a conventional furnace with a Hitachi Zeeman system forAs compounds. They found different calibration curves for Asdepending upon the compounds. We believe that the platform tech-nique will remove the matrix dependence and improve the stabilityof the calibration.

Woolson el aL (973) separated arsenicals by LC and detected theAs compounds by using a conventional autosampler and the HGA-2100 furnace. A bar graph representation of the chromatogramresulted.

BariumFrom data derived from the appearance temperature of Ba, Nag-

daev and Bukraev (610) believed that BaO dissociated after subli-mation from the graphite. However, Jasim and Bar boot i (375)believed that Ba proceeded to the atomic vapor by the carbon disso-ciation of the oxide to solid or liquid Ba which is then volatilized.

Barium is an interesting spectroscopic determination. It is. per-haps, slightly more sensitive by emission (205,873) than by absorp-tion. It requires a high temperature for vaporization and is gener-ally recommended from the wall of the furnace instead of from theplatform (780j). In early work, Renshaw (719) showed that Ba wasvery much more sensitive in the HGA-70 furnace if the tube waslined with Ta foil as compared to unco a ted graphite tubes availableat that time. Probably new pyrolytically coated tubes are the sameas vaporization from a Ta surface. Because the vaporizationrequires a high temperature, Ba is improved by rapid heating andFernandez and lannarone (236) showed an improvement of about50%. Their improvement for pyrolytic graphite over uncoated graph-ite is almost 15-fold. Because Ba requires a high furnace tempera-ture and the resonance line is at a long wavelength (553.6 nm) thedetermination benefits from a narrow spectral slit width to reducethe continuum radiation from the wall. The lamp should be verybright or the determination will be noisy. Since the lamp must bebright and the wavelength is long, the deuterium background cor-rector is not useful at the Ba wavelength. The modern instrumentsthat use a tungsten-iodine lamp for background correction at thelong wavelength determinations now make Ba an important furnacedetermination. The Zeeman background correction should be par-ticularly useful for Ba.

79