445-446A selective spectrophotometric method based on the interaction of an anionic iodo complex of cadmium with methyl violet has been described for the determination of trace amounts of cadmium. The developed method is precise, accurate and has been applied to determination of cadmium at trace levels (25 ppb) in sea water and high purity samples of indium and zinc materials

Damodaran, A O

Iyer, C S P

Nair, D Sreevalsan

Rao, T Prasada

English

NOPR

IndianJournalof ChemistryVol.33A, May 1994,pp.445-446Spectrophotometricdeterminationoftraceamountsof cadmiumwithiodideandmethylvioletD SreevalsanNair, T PrasadaRao*, C S P Iyer &A 0 DamodaranRegionalResearchLaboratory(CSI R), Trivandrum695019Received20July 1993;revised2 September1993;accepted10November1993A selectivespectrophotometricmethodbasedonthein-teractionofananioniciodocomplexofcadmiumwithme-thylviolethasbeendescribedforthedeterminationftraceamountsofcadmium.Thedevelopedmethodisprecise,accurateandhasbeenappliedtodeterminationfcadmi-umattracelevels(25ppb)in seawaterandhighpuritysamplesof indiumandzincmaterials.Thehazardouseffectsofcadmiumarewelldocumen-ted1- 3.However,it findswideuseasanantifrictionagent,rust proofer,cooling agentin enamelandpaintsandinplasticmanufactureandstoragebatteri-es.Hence,it isnecessarytodeterminethiselementattracelevels.Many of thespectrophotometricmethodsrepor-tedfor thedeterminationof cadmiumaretedious4andnotselective5,6.Someothermethodsbased0ntheinteractionoftetraiodocadmate(I1)anion7.8andbis-(phenanthrolineum)cadmium(I1)cation9•lowithdy-estuffsofoppositecharge,thoughsensitiveareinade-quateforpracticalanalysisduetointerferencefromotherelementsthatarefrequentlyencounteredwithcadmium.Thepresentstudyshowsthatthelllteractionoftet-raiodocadmate(I1)with methylviolet providesamoresensitivemethod(8=1.5x 1051mol-I cm-I)than thosebasedon reactionwith pyronineG7(8=9.0><;104 I mol-I cm-I) or rhodamine6 G8(8=8.9x 104'1mol-I cm-I). The methodhasbeenappliedforthedeterminationofcadmiuminseawa-terandhighpurityzincandindiummetalsamples.Interferingionshavebeensuccessfullyeliminatedbysuitableconditioningofthesolutionpriortospectro-photometricdetermination.ExperimentalA Hitachi220microcomputerbasedspectropho-tometerwith10mmmatchedquartzcellswasusedforallthespectralmeasurements.An ELiCO L1-120di-gitalpH meterwasusedforpH adjustments.All re-agentsusedwereofAR gradeunlessotherwisestated.All solutionswerepreparedwithdoublydistilledwa-ter.A stocksolutioncontaining500ppmofcadmiumwaspreparedbydissolving0.2854gof3CdS04.8 H20in250mlofwater.Thesolutionwassuitablydilutedtoobtainastandardsolution(5ppm)ofcadmium.Asolutionof sodiumcitrate(I M) adjustedtopH 4.0withOCI wasusedasthebuffer.A 5%aqueousolut-ionofKI and0.01% aqueousolutionofmethylvio-letwerealsoprepared.An aliquot(up to 15ml) of thesamplesolutioncontainingnotmorethan511gofcadmiumwastakenina25mlstandardflaskandtreatedwith2.5mlofthecitratebuffer(pH4.0).Potassiumiodideandmethylviolet(2.5ml each)wereaddedto theflaskandthevolumewasmadeupto25mlwithdistilledwater.Theabsorbancewasmeasuredm10mmcellsat590nmagainstareagentblank.A calibrationgraphwasplot-tedfor0-5I1gofcadmiumstandardsolutionsbytheaboveprocedure.Analysisof highpurityzincandindiummetalsZincorindiummetal(5.0g)wasdissolvedin20mlof I: 1HCl andmadeupto 100m!.Suitablealiquotscontainingcadmiumin therange0-5I1gweretakenandasolutionofsodiumcitrate(20%,2ml)wasadd-ed.ThepH wasadjustedto 4.0usingapH meter,beforetransfrringintothe25mlcalibratedflaskandanalysingasabove.ResultsanddiscussionTheabsorptionspectraofCd-r -methylvioletcom-plexwasrecordedagainstthecorrespondingreag-entblank.The ternarycomplexwasfoundto haveAmax at 590nm.It wasfoundthattheformationoftheternarycom-plexwascompletein thepH range3.0-6.0.Citratebufferwaspreferredtophthalateoracetatebufferasitspresenceremovestheinterferencedueto200-foldexcessofPb2+, Sn2+andSb3+. Forthedeterminationf0.1ppmofcadmium,constantandmaximumabsorb-ancerequiredadditionofatleast2.0mlof 5%KI and2.0mlof 0.01% methylviolet.Undertheseoptimalconditions,thecolourdevelopmentwasinstantane-ousandremainedstablefor24hr.Theorderofaddi-tion of reagentswasnot critical.Thecalibrationgraphwaslinearovertherange0-5I1gofcadmiumpresentinatotalvolumeof25m!.Themolar absorptivity(8) was found to be 1.5x 105I mol-I em-I.IIINDIAN J CHEM, SEe. A, MAY 1994446Table I---Analysis of sea water samples Table 2-Analysis of high purity metalsTen rellicate determinationsof standardsolutionscontaini g 2.5 f.1gof cadmium showed a meanreco-veryof 1 0.25% with a relativestandarddeviationof2.9%.The c hiningratio of cadmium to methyl violetwas fou d to be 1:2 from molar ratio, continuousvariatio and slope ratio methods. These methodswereuns ccessfulwhenusedfor thedeterminationofthecom .ning ratio of cadmium to iodide, asno col-our deve pmenttook placewhentheywerepresentin ms:>larroportions. However, theequilibrium shiftmethod i dicated a cadmium to iodide ratio of 1:4.2.50.1355.0280NaCI (20°%0)100.000102.5 45 0 73Sea water13(1.05°;'), K (0.04%)52.5 4Mg(3.77° ),Ca I.3%)CI (1.89%Deep seaater 10 1(3.2(~,K(O.6 %),Mg (3.67° , Ca (1.3%)CI 7%)Hl1 5o onShangumm, Tvm2T p water. 1;2 5lnterf'erecestudiesA stu on interfering effectsof various ions (200ppm) on he determination of 0.1 ppm of Cd by thepropose methodrevealedthatLi +,Na +, K +, Ca2+,Sr2+,Ba +,Mg2+,Pb2+, Sn2+,Cu2+,Zri2+,Fe2+,Be2+;Ni +,C02+,Vo~+, Mn2+, Cr3+, Fe3+,A13+,Sb3+,Ti +, La3+, Ce-l+, ZrH, Th-l+, Te.J+, Se.J+,Sb5+, sot, . AsOj - , VOJ - , WO~- , SO~- ,S20~- , 40~-, F-, SCN -, oxalate, tartrate, 1-,Br - and OJ - do not interfere.The a dition of 2 ml of 5% thiourea eliminatedinterfere cedue to Pd2+and Pt4+,while 5ml of 5%sodium uoride removed interference due toMoO~- . einterferencedueto Hg2+ wasovercomehyreductio with 2.5ml of2%SnCh and centrifugingtheturbi solutionprior to addition of reagentsoluti-on. The a dition of2 ml of 5% urearemovedinterfer-ence due to nitrite...,..Amount of AliquotCd found (l1g/g)Cd addedtaken(l1g/g)(m!)ProposedASjmethodSS MS*10.01.61.62.50.04 1.53.33 25.02 82 81 250455 410..35*,.2.599* ..Zn granulesSampletZn oxidet5 gjlOO ml*Spark Source Mass SpectrometryIndium metalAnalysisof'syntheticandrealsamplesTable I presentstheresultsof theanalysisof synthe-tic sample solutions of various forms of sea waterafter eliminating the interferencesasdescribedabo-ve.The resultsclearly show that the method can beusedfor traceleveldeterminationof cadmiumin poll-uted sea water samples.Sincethemetalionscommonlyassociatedwithcad-mium,viz.,Zn2+,Pb2+,Cu2+,FeH ,Ce4+,InHandWO~-do not interfere,theproposedmethodcanbeusedfordetermination of cadmium in real sampleslike highpurity indium metal,zinc granulesandzinc salts(Ta-ble2).The resultsobtainedhavebeencomparedwiththoseobtainedusingAAS and sparksourcemassspe-ctrometry. The data obtained on thesamplesspikedwith known amountsof cadmiumarealsopresented.The results show good agreementbetweenthe twomethods.AcknowledgementThe authorsthank theDepartmentof OceanDeve-lopment, New Delhi, for providing funds.ReferencesI Purve D. Tracl' 1'11'/111'111' mn/amina/ion o/,/hl' I'nvironml'n/(Elsevier, New York). 1977,p. 20.2 Kolthoff I M & Elving P J. Trm/isl' on imaly/ical chl'mis/ry(Wiley-Interscicnce. New York). 1970.p. 80.3 Patty F A, Indus/rial hrgienl' and /oxicology, Vol. 2 (Wiley-Interscience. New York), 1962.pp. 1011.4 Silverman L & Trega K. AI/all's/. 77 (1952) 143.5 Michayle'/a V, AI/al Chilli AC/(l. 68 (1974) 73.6 Hsu C G, Talan/a. 27 (1980) 676.7 Rao T P & Ramakrishna T V, Al/all'.I/. 107(1982) 704.8 Kartikeyan S, Rao T P, Iyer C S P & Damodaran A D. Talan/a,40 (1993) 771.9 Tananaiko M M & Bilenko N S, Zh Anal Kllim, 34 (1979)1988.10 Buhl F & Mikula B. C/WIII AI/aI, 23 (1983) 779.Cd added Absorbance(l1g in 25 mlsolution)Aliquottaken(ml)Composition of thesampleill

Spectrophotometric determination of trace amounts of cadmium with iodide and methyl violet

http://nopr.niscair.res.in/bitstream/123456789/40851/1/IJCA%2033A%285%29%20445-446.pdf

Spectrophotometric determination of trace amounts of cadmium with iodide and methyl violet

Abstract

Similar works

Full text

Available Versions

NOPR