Determination of gold by graphite furnace atomic absorption spectrometry after coprecipitation with nickel diethyldithiocarbamate

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Determination of gold by graphite furnace atomic absorption spectrometry after

coprecipitation with nickel diethyldithiocarbamate

著者 Sato Hirotoshi, Ueda Joichi journal or

publication title

Analytical Sciences

volume 16

number 10

page range 1089‑1091

year 2000‑01‑01

URL http://hdl.handle.net/2297/3903

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1089 ＡＮＡＬＹＴＩＣＡＬＳＣＩＥＮＣＥＳＯＣＴＯＢＥＲ２０００,VOL16

2000oTheJapanSocietyfOrAnalyticalChemistry

Noles

DetermimtionofGoldbyGmphiteFumaceAtomicAbsorptionSpectrometry afterCoprecipitationwithNickelDiethyldithiocarbamate

HirotoshiSAToandJoichiUEDA

FiZcDJ/jyq/、/"carjo",KZJ"αZaWaU7zjveﾊﾉﾉMmlc"ｍａ－ｍａｃ/tj,KbJ"αZawa920-II92,ﾉﾋﾘPα〃

(ReceivedMayl5,2000;AcceptedJuly24,2000）

2％DDTCsolutionisaddedwithstirrinｇｔｏａｓａｍｐｌｅｓｏｌｕｔｉｏｎ

(ｕｐｔｏｌＯＯＯｃｍ３）containing30-llOOngofgold;thepHis adjustedtoabout9withaqueousammonia(1+3)．Tosettlethe producednickelDDTC，ｔｈｅｓｏｌｕｔｉｏｎｉｓａｌｌｏｗｅｄｔｏｓｔａｎｄｆＯｒa

fewmin，subsequently，theprecipitateiscollectedona3G4

sintered-glassfilter・Aftertheprecipitateiswashedwithasmall

amountofdistilledwater,１cm3nitricacid(1＋l)ispouredonto

theprecipitate．Withinafewmin，theprecipitateis

considerablydissolved,turningincolorfromyellowish-greento brownThen，１cm3ofacetoneisaddedtocompletelydissolve

theprecipitateandthesolutionisdilutedtolOcm3withdistilled waterlfturbidityappearsinthefinalsolution,tｈｅｕｓｅｏｆ２ｃｍ３

ｏｆａｃｅｔoneisreconⅡnendedTheatomicabsorbanceofgoldis measuredundertheoperatingconditionsgiveninTableLA blankisalsorunusingdistilledwaterasasamplesolution．

＆ ThecoprecipitationmethodiswidelyusedfOrtheconcentration oftracemetalionspriortotheirgraphitefUrnaceatomic

absorptionspectrometricdetermination，andavarietyof cOprecipitantshavebeenstudiedForthepreconcentrationand separationofgoldpriortoagraphitefUrnaceatomicabsorption spectrometricdetennination，telluriuml-6andmercury7-9have

untilnowbeenproposedascoprecipitants・However,theuseof telluriuml-6isdisadvantageous,becauseitisnecessarytoheata

samplesolutiontocompletereductivecoprecipitationandfOr theresultantprecipitatetodissolveonlyslowly、Theuseof

mercury7-9isalsoundesirablebecauseofitstoxicity・

Inapreviouspaper,lotheauthorsproposednickel diethylditmocarbamate（nickelDDTC）asacoprecipitantfOr

cadmium，becauseofitsgoodcollectingability，easeof dissolutioninnitricacid（l＋Dandacetone，andselectivity；

nickelDDTChardlycoprecipitatesalkaliandalkalineearth metals・Wehavefbundthatthiscoprecipitantisalsoan excellentcollectoroftraceamountsofgold,andovercomesthe

weakpointsofthecoprecipitantsmentionedabove・l－９Ｔｈｅｕｓｅ

ｏｆｎｉｃｋｅｌＤＤＴＣａｌｓｏｄｏesnotcauseinterferenceinthegraphite fUrnaceatomicabsorptionspectrometricdeterminationofgold、

Themethodproposedhereissimpleandreproducibleand applicabletotheanalysisofriver，taporsea-watersamples

whichcontａｉｎｓｄｏｗｎｔｏ３０ｐｇｃｍ－３ｏｆｇｏｌｄ

ＴｈｉｓｐａperdescribesthefUndamentalconditionsfOrthe coprecipitatiｏｎｏｆｔｒａｃｅａｍｏｕｎｔｓｏｆｇｏｌｄｉｎｗａｔｅｒｗｉｔｈｎｉｃｋｅｌ

ＤＤＴＣａｎｄｆＯｒｔｈｅｇｒａｐｈｉｔｅfUrnaceatomicabsoIption spectrometricdeternnnationofgold．

ResultsandDiscussion

。P伽皿mco"伽o"s/brcOPreciPj伽o〃

Eｶﾞ12crq/伽ａｍｏＭ"rq/cOprecjp伽"fThenecessaryamount ofnickelDDTCfOrcoprecipitationwasstudiedwithasample solution（５０－１０００ｃｍ3)containing500ngofgoldForthe

quantitativerecoveryofgold，thecomplexationof2mgof

nickelwiｔｈＤＤＴＣｗａｓｎｅｃｅｓｓａｒｙｆＯｒｕｐｔｏｌＯＯＯｃm3ofa

samplesolution・ＳｉｎｃｅｔｈｅｕｓｅｏｆｕｐｔｏａｔｌｅａｓｔｌＯｍｇｏｆnickel

didnotaffectthedeterminationofgold，３ｍｇofnickelwas selectedinthisstudy・ＴｈｅｕｓｅｏｆｕｐｔｏｌＯｃｍ３ｏｆａ２９６ＤＤＴＣｓｏｌｕｔｉonalsodidnotinfluencethegolddetenninationThus,２ cm3ofit,corespondingtoabout3-times(asamoleratio)３ｍｇ

〃と

Experimental

Ａｐｐａｍｍｓ

Ａ'’oftheapparatusemployedinthisworkweredescribedTablclRecommendedoperatingconditionsforthe

absorptionspectrometer previouslｙＩｏ

aｔｏＨｕｃ

242.8ｎｍｌＯｍＡＮｏ２(1.1,ｍ）

Analyticalwavelength LampculTent Slitwidth

Argongasflowrate Sheathgas Carriergas lnjectionvolume

Cuvette

ReczgemS

Thereagentswerethesameasthosedescribedpreviously,lo

exceptfOrthatmentionedbelow・

Asolutioncontainingaboutlmgcm-3ofgoldwasprepared

bydissolvingchloroauncacidtetrahydrateindistilledwater、

Theconcentrationofgoldwasdeterminedbycomplexomemc back-titrationwithastandardmanganese(Ⅱ）solutionusing

EriochromeBlackTasanindicator．

３dm3min-l Odm3min-l

lOmm3

uncoatedtubetype graphitefUmace 21A(ｃａｌ50°Ｃ),４５ｓ８０Ａ(cα､700°Ｃ),９０ｓ 280Ａ(cα2700°Ｃ),５ｓ Dryingconditions

Ashingconditions Atomizingconditions 舵comme"dedpmce〃re

Anaqueoussolutioncontaining3ｍｇｏｆｎｉｃｋｅｌａｎｄ２ｃｍ３ｏｆ

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ＡＮＡＬＹＴＩＣＡＬＳＣＩＥＮＣＥＳＯＣＴＯＢＥＲ２０００,ＶＯＬ１６ 1０９０

Table2Effectofdiverseionsontheｄｅｔｅｒｍｉｎａｔｉｏｎｏｆ５００ｎｇｏｆＴａｂｌｅ３Ｒｅcoveryofgoldfromspikedwatersamples

gold _ＲＳＤ，

％ AufOundノ

、９ Auadded／

、９ Sample

volume/cｍ３ Massratioa

Uon]/[Au］ ^loｎ

Riverwatera lOOO TapwateF

１０００ Seawater

lOOO １０００

3.9 2.2 30.1

30.8 3０

３０Ｃｌ－

Ｎａ＋

Ｋ十

Ｍ92+,Ｃａ2＋

Ｂｒ-,1-,ＳＯ４２－

Ｆ

ＰＯ４３－

Ｌｉ+,Be2+,Sr2+,Ｂａ2+,Ａｌ3+,Ga3+，

pb2+,Sb3+,Ｂｉ3+,Ｃｕz+,Ａｇ+,Ｚｎ2+，

Cd2+,La3+,Ｃｅ3+,Ｚｒ4+,Th4+,MovI，

Wvl,Cr3+,Ｍｎ2+,Fe3+,ＣＯ２＋

Rh3+,Ir4+,Pd2+,Ｐｔ'v ln3+,Sn4＋

3700000 2400000 1000000 500000 200000 20000 ４０００２０００

30.9ｂ４９８９ｂ

2.2 1.5 ３０

５００

Theobtainedrecovenesaretheaverageofthreereplicatedeterminations、

ａＴｈｅａｍｏｕｎｔｓｏｆｇｏｌｄｉｎｒｉｖｅｒａｎｄｔａｐwaterwerelessthanthedetection limitoftheproposedmethod

b・Therecoveriesofgoldwerecalculatedbysubtractingthepeakheight duetoseawateralonefromthatduetoseawaterspikedwithgold．

200

ThecoprecipitationwascarriedouｔｆｉＰｏｍａｂｏｕｔ８０ｃｍ３ｏｆｔｈｅｓａｍｐｌｅｓｏｌutionatapHofabout9．

ａ・Theerrorsarewithin±5％．

fOrthepeakheightsobtainedfromfiverepeateddeterminations Ｉへ

waｓ２４９ＭＯｒ５００ｎｇｏｆｇｏｌｄｉｎａｂｏｕｔ３００ｃm3ofthesample solutionThedetectionlimit(signaltonoise=2)ｗａｓ６ｐｇｃｍ－３ｏｆｇｏｌｄｉｎｌＯＯＯｃｍ３ｏｆｔｈｅinitialsamplesolution．

ofnickel，wasusedfOrcoprecipitation，ｂｅcausethemoleratio ofnickeltoDDTＣｉｎｔｈｅｃｏｍｐｌｅｘｗａｓｃｏｎｆｉｒｍｅｄｔｏｂｅｌ:Zby elementalanalysis、ThetimerequiredtofilternickelDＤＴＣｆｒｏｍｌＯＯＯｃｍ３ｏｆｔｈｅｓａｍｐｌｅｓｏｌｕｔｉｏｎｗａｓａｂｏｕｔｌＯｍｉｎ・ＩｎｔｈｅｃａｓｅｏｆｕｓｉｎｇａｖｏｌｕｍｅｏｆｍｏｒｅｔhanlOOOcm3ofsample solution，ｈowever，nickelDDTCgraduallybecameafinely dispersedprecipitate,andmorethan60minwasrequiredfOrits filtrationfrom2000cm3ofthesamplesolution、Thus,ａｎｕｐｐｅｒｌｉｍｉｔｏｆｌＯＯＯｃｍ３ｏｆｔｈｅｓａｍｐｌｅvolumewastakeninthis expenmenL

Eﾘｸﾞ12ｃｔｑ／此ｐＨｏ〃cOp'qecjP伽rjo"・NickelDDTC coprecipitatedgoldquantitativelyoverawidepHrangefrom ２．４ｔｏ10.5．ApHofabout9wasusedfOrthecoprecipitationof goldinfnrtherexperiments，becausenickelDDTCobtained aboveａｐＨｏｆａｂｏｕｔ８ｗａｓｂｕｌｋｙ，andhenceeasytohandle TYIeIccoveryofgoldreachedalmostlOO96about2minafter thefOnnationofnickelDDTCandtherecoveryremained almostunchangeduponstandingfOratleast3hThus，the precipitatewasfilteredaftersomesettlementhadoccurred D伽o伽o〃ｑ/〃jcMDDTCItisdifficulttodissolvethe precipitateofnickelDDTCinｃｏｍｍｏｎmineralacidsatroom temperature、However，itcanbeeasilydissolvedwithnitric acid（1＋1）andacetonewithoutanydigestionorheatingloln thisexpenment,１cm3eachofnitricacid(1＋1)andacetonewas usedtodissolvetheprecipitate,sincetheadditionofO・Ｓ－３ｃｍ３ｏｆｎｉｔｒｉｃａｃｉｄ(1＋1)andO5-4cm3ofacetonedidnotaffectthe goldabsolptionlfthefinalobtainedsolutionbecomesturbid，

theuseof2cm3ofacetoneisrecommended．

I7zre旅だ"ces

Theinfluenceofeachof39diverseionsonthedetermination

ofgoldｉｎａｂｏｕｔ８０ｃｍ３ｏｆａｓａｍｐｌｅｓｏｌｕｔｉｏｎｗasexamined accordingtotherecommendedprocedure(Table２)．Goldcould bedetenninedwithina±5％errorinthepresenceoflarge amountsofsodiumpotassium，magnesium，calcium，fluoride，

chloride,bromide,iodide,sulfate,andphosphate,aswellaslM Ugofindiumandtin(1V)．Nootherionstestedproducedany seriousinterferenceeffect,evenataconcentration2000-times themassofthegoldpresent．

RecolﾉCDﾉq/goJd/>９０"zsomeSpj舵｡ｗα花芯α叩ﾉes

Toevaluatethepotentialofthismethod，therecoveriesof goldfromnver，tap，andsea-watersamplesspikedwithgold wereexaminedTheresultsobtainedbythecalibrationmethod weresatisfactory，whichindicatesthattheproposedmethodis applicabletoanalysesofthesewatersampleswhichcontain downto30pgcm-3ofgold(Table３)．

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Ｍ.Etoh,Ｂ""sekjKZJgak",1990,39,Ｔ５．

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●●●□ ■■二■△〔｝〃〆』（〃、０）△句、」。 ● ● ● ● ｜』、，》一々【叩）［囮〃，，（叩）（）

Ｃａﾉﾉb）acJrjo〃ｃ"ハノe

Alinearrelationship,passingthroughtheorigin,betweenthe peakheightandtheconcentrationwasobtainedfrom30tollOO ngofgoldinthefinalsolution（１０ｃｍ3)．Thiscalibrationcurve wasalmostthesameasthatwhichwaspreparedwithoutthe coprecipitationprocedure，usingastandardsolutioncontaining vanousamountsofgold，３ｍｇｏｆｎｉｃｋｅｌ，Ｚｃｍ３ｏｆ２９６ＤＤＴＣｓｏｌｕｔｉｏｎ，ｌｃｍ３ｏｆｎｉｔｒｉｃａｃｉｄ，ａｎｄｌｃｍ３ｏｆａｃｅｔｏｎｅｉｎｌＯｃｍ３、

Thereproducibilityofthismethod(relativestandarddeviation）

●● （卯〕”〉（凪理叩）●■■ユ