Liquid-phase microextraction–gas chromatography–mass spec(7)

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K.Reddy-Nooneetal./J.Chromatogr.A1148(2007)145–151

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Fig.5.GC–FIDforthedeterminationof5 gl 1ofbromate.TheGCcol-umnwasHP-5(5%phenylsubstitutedmethylpolysiloxane)30m×0.32mm; lmthickness0.25 m,capillarycolumn;oventemperaturewasheldat90 Cfor3min,programmedto220 Cat20 Cmin 1andheldforfurther2min;carriergasnitrogen,3mlmin 1;hydrogen,25–30mlmin 1,andair,250–300mlmin 1.LPMEin50 loftoluene,injectionvolume,2 l,splitless.

e.g.bysolid-phaseextractionwithLiChrolutENcartridgebeforederivatization.Reducingionsdeplete2-iodosobenzoateleadingtoincompletederivatizationreaction.Thissituationwasavoidedbyemployingalargeramountsof2-iodosobenzoatereagent,orbymixingthesampleswith500 lof20%hydrogenperoxidebeforeaddingotherreagents.Sul de,thiosulfate,sul- te,thiocyanate,nitrite,iron(II)andmanganese(II)producednotmorethan3–5%errorwhenpresentuptoa3-fold(m/m)excessoverbromate/bromideandiodate/rgeexcess,atleast1000-fold,ofchloride,bromide,nitrate,phosphate,perchlorate,sulfate,hydrogencarbonate,ammonium,calcium,magnesium,zinc,cadmiumandcobaltcouldbeavoided,theerrorwasnotmorethan2–3%.

Besidesremovingbromideandiodide,prereactionwithAgClhasalsobeeneffectiveinremovingcertainotherinterferingionsowingtolowerKspoftheirsilversaltsthanthatofAgCl;examplesinclude(Kspofrespectivesilversaltinparentheses)cyanide(2.2×10 16),thiocyanate(1.0×10 12)andsul de(1.0×10 50).4.Conclusions

TheproposedmethodinvolvinguseofAgClforremovalofbromideandiodide,anddeterminationofbromateandiodatebytheirreductionandconversion,respectivelyinto4-bromo-and4-iodo-2,6-dimethylanilineisasimpleandconvenientprotocolofanalysis,anditavoidsmanyinconveniencesofionchromatog-raphy.The4-bromo-and4-iodo-2,6-dimethylanilinearegoodcandidatesforliquid-phasemicroextractionandanalyzingtheextractsbyGC–MSproducedsensitivedetectionatngl 1levelofanalyteions.LPMEwith50 lofsolventhasbeenfoundtobemorerobustandtogivebetterextractioninshorterperiodthanSDME.Acknowledgement

A.J.thankstheDepartmentofScience&Technology,NewDelhi,fortheawardofaresearchgrantunderWomenScientistScheme(SR/WOS-A/CS-02/2004).References

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