homemade high exchange by ion chromatography with UV detection离子色谱
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Asinglepumpcycling-column-switchingtechniquecoupledwithhomemadehighexchangecapacitycolumnsforthedeterminationofiodateiniodizedediblesaltbyionchromatographywithUVdetection
ZhongpingHuang,QamarSubhani,ZuoyiZhu,WeiqiangGuo,YanZhu⇑DepartmentofChemistry,XixiCampus,ZhejiangUniversity,Hangzhou310028,China
articleinfoArticlehistory:Received28July2012Receivedinrevisedform12December2012Accepted27January2013Availableonline6February2013
Keywords:IodateIodizedediblesaltCycling-column-switchingIonchromatography
abstractAsinglepumpcycling-column-switchingtechniquehasbeendevelopedfortheiodateanalysisinediblesalt.Homemadehighexchangecapacitycolumnswereadoptedfortheseparationofiodateandchloride.Iodatecouldberetainedandconcentratedinahomemadeconcentratorcolumnaftereluentspassingthroughthesuppressor.WithUVdetection,iodateexhibitedsatisfactorylinearityintherangeof0.1–10.0mg/Lwithacorrelationcoefficientof0.9996.Thedetectionlimit(LOD)was45.53lg/L,basedonthesignal-to-noiseratioof3(S/N=3)anda100lLinjectionvolume.Relativestandarddeviations(RSDs)forretentiontime,peakareaandpeakheightwerealllessthan2.1%.Recoveriesofaddediodatewereintherangeof98.4–101.6%forthespikedsamples.Thequantitativedeterminationofiodateinediblesaltwasaccomplishedbythiscolumn-switchingtechnique,withoutanypretreatmentandinterference.Theresultsonsixsampleswerestatisticallycomparedwithresultsdeterminedbyconventionaltitrimetricmethod.Ó2013ElsevierLtd.Allrightsreserved.
1.IntroductionIodineisoneoftheessentialtraceelementsforproducingthy-roidhormonesinthehumanbodyandinsomeotherbiologicalspecies(Buchberger,1988;Yao,Chen,&Wei,1999).Excessiveio-dineintakecancontributetocertainthyroiddisordersinsuscepti-bleindividuals,whereasadeficiencyofiodineinthedietcancauseseveraldiseasesorproblems,whichincludespontaneousabortion,increasedinfantmortality,cretinism,andstuntingofintellectualfunctioning(Delange,Bürgi,Chen,&Dunn,2002;Eckhoff&Maage,1997).Forthecontrolofgoitre,saltforediblepurposeiscompul-sorilyiodizedbycoatingKIO3onsaltcrystalsandtherecom-
mendedconcentrationofiodateinthesaltisabout40ppm.Today,iodizedsaltisanimportantsourceofiodineandcookingwithiodizedsaltishighlypromotedinChinaandmanyAsiancountries.Severalmethodshavebeendevelopedfortheestimationofio-dineiniodizedediblesalt.Conventionaliodometrictitration(Cunniff,1990,chap.11)wasappliedeasilybothinthelaboratoryandinthefield,basedontheredoxreactionbetweeniodateandiodidetogiveI2thatcanthenbetitratedwiththiosulphateion.
However,titrationdemandedofhighskillofoperatorsandwasatime-consumingprocess,especiallyintheprocessesofpreparingandstandardizingthetitrantofthiosulfatesolution.Additionally,
thetitrationmethodmightgivefalseestimateofiodatewithoxi-dizingagentssuchasbleachingpowder(Rebary,Paul,&Ghosh,2010).Specialchemicalreagentsandcomplicatedreactionswereinvolvedinspectrophotometricdetectionofiodateiniodizedediblesalt(Borges,Peixoto,Feres,&Reis,2010;Shabani,Ellis,&McKelvie,2011;Xie&Zhao,2004).Estimationofiodateiniodizedediblesaltbytransientisotachophoresis-capillaryzoneelectro-phoresishasbeenreportedrecently,withcarcinogenicchromateionasaninternalstandard(Wang,Zhao,Shen,Tang,&Wang,2009).ReductionofiodatewasnecessaryintheHPLCdetectionofiodateiniodizedediblesalt(Xu,Li,Gu,&Paeng,2004).Electrochemicaldeterminationwithmodifiedelectrodehasbeenaccomplishedwithunsatisfactoryrelativestandarddeviation(Kosminsky&Bertotti,1999).Theuseofionchromatography(IC)islimitedfordirectdeter-minationofiodateiniodizedediblesalt.Thehighchlorideconcen-trationofthematrixdoesnotpermitacleanseparationandconductimetricdeterminationofiodateinediblesalt.Aftersamplepretreatmentwithon-guardsilvercartridgefortheremovalofthelargeexcessofchlorideion,iodateinediblesaltwassuccessfullydeterminedbyICwithconductivitydetection(Kumar,Maiti,&Mathur,2001).Unfortunately,afreshAgcartridgewasrequiredforeachsample.Inaddition,itwasnecessarytoreduceiodatetoiodideinestimationofiodateiniodizedsaltbyICwithintegratedamperometricdetection(Rebaryetal.,2010)orUV/visibledetection(Bichsel&Gunten,1999;Weinberg&Yamada,1998).Iodateinediblesaltorseawaterhasbeenestimatedusing
0308-8146/$-seefrontmatterÓ2013ElsevierLtd.Allrightsreserved.http://dx.doi.org/10.1016/j.foodchem.2013.01.070
⇑Correspondingauthor.Tel./fax:+8657188273637.
E-mailaddress:zhuyan@zju.edu.cn(Y.Zhu).
FoodChemistry139(2013)144–148ContentslistsavailableatSciVerseScienceDirectFoodChemistry
journalhomepage:www.elsevier.com/locate/foodchem