电极-抛光
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Amethodforinsituauto-renewalofthesurfaceofglassycarbonelectrodes
QingmanLia,b,*,ShupingBia,GuoliangJibaDepartmentofChemistry,NanjingUniversity,Nanjing210093,PRChina
bInstituteofSoilScience,ChineseAcademyofSciences,Nanjing210008,PRChina
Received26November2002;receivedinrevisedform4June2003;accepted11June2003
AbstractDepositionofelectrolyticproductsandcontaminationmaychangethesurfaceconditionofaglassycarbonelectrode,theworkingelectrodeinvoltammetricmeasurements.Amethodforinsituauto-renewalofthesurfacewasdevelopedtoobtainre-produciblefreshsurfaces.TheanalyticalapplicationofthismethodwasverifiedbydifferentialpulsevoltammetricdeterminationofFe(II).Thedeterminationexhibitedareproducibilitysignificantlybetterthanthatwithun-renewedelectrodesorthoserenewedmanually.Theresultsofthevoltammetricdeterminationcorrelatedwellwiththosefoundbyacolorimetricmethod(r¼0:9989).TherecoveryofFe(II)addedtosoilsolutionrangedfrom98%to104%.Themethodmayfindapplicationsinthedeterminationofreducingsubstancesandstudiesonchemicalreactionkineticsinclosedsystems.Ó2003ElsevierB.V.Allrightsreserved.
Keywords:Glassycarbonelectrode;Renewalofelectrodesurface;Voltammetry
1.IntroductionVoltammetrywithsolidelectrodeshasbeenintro-ducedtosoilandaquaticsciencesformulti-elementdeterminations,speciesanalysisandstudiesonorganicreducingsubstances[1–3].Itisalsosuitableforon-lineorfieldmeasurements[1,3].Inthismethod,themostcommonlyusedworkingelectrodesarecarbonelec-trodes,notablyglassycarbon(GC)electrodes.Inaddi-tiontoeasyhandlingandasmallresidualcurrent,theGCelectrodepossessesanimportantfeatureinthatithasawidepotentialrange,particularlyonthepositivepotentialside.Thisfeatureisveryvaluableforuseinsoilandaquaticsystemsinwhichoxidation–reductionpropertiesareofcommonconcern.Ontheotherhand,thesurfaceofGCelectrodescanadsorborganicandinorganicspeciesfromthesolution[4–8].Duringuse,theelectrolyticproductswouldalsoaccumulateonit[1].Thefreshsurfaceofanewlypre-
paredelectrodemayevendeactivatewithtimeonex-posuretoair[4,8–10].Thesechangesinsurfacepropertieshinderedelectrontransferbetweentheelec-trodeandthesolution,resultingindecreasesinsensi-tivityandresolution.Therefore,havingafreshsurfaceisaprerequisitefortheGCelectrodepriortoitsuseinanelectrochemicalmeasurement.InordertoobtainafreshsurfaceoftheGCelectrode,variousmethodshavebeendeveloped.Reviews[10,11]havealsoappeared.Thesemethodsincludemechanicalpolishing,chemicaltreatmentandelectrochemicaltreatment[1,11,12].Othermoreexoticmethodsincludeheattreatment[13,14],radio-frequencydischarge[15],laserirradiation[12,16],exposureofthefreshbulkcarbonsurfacebyfracturingaGCrodinsitu[13]andUV/ozonetreatment[17].Ofthesemethodsthemostcommonlyusedoneismechanicalpolishing.Thepol-ishingcanbeaccomplishedmanuallywithaluminaordiamond[4–6,8,15–24]orsemi-automaticallywiththeaidofametallographicpolishingwheel[13,25].Allthesepolishingmethodsaretediousandtime-consuming.Also,itisdifficultforreproduciblesurfacestobe
JournalofElectroanalyticalChemistry560(2003)19–23www.elsevier.com/locate/jelechem
JournalofElectroanalytical
Chemistry
*Correspondingauthor.Fax:+25-688-1000.
E-mailaddress:liqm@nju.edu.cn(Q.M.Li).
0022-0728/$-seefrontmatterÓ2003ElsevierB.V.Allrightsreserved.doi:10.1016/j.jelechem.2003.06.003obtainedbyinexperiencedworkers.Toovercometheseproblems,someautomaticdeviceshavebeencon-structed.Forexample,Cardwelletal.[26]havedesignedadeviceforusewithmicroelectrodes.EG&GPrincetonResearchalsoproducesdevicesformicroelectrodes.However,thesedevicescanonlybeusedforspecificpurposes.Therefore,atpresent,fortheIUPAC,nostandardpretreatmentprocedureforsolidelectrodeshasbeenproposed.ToobtainanactiveandreproduciblesurfaceofsolidelectrodesincludingGCelectrodesisstillanenduringthemeinelectroanalyticalchemistry[11].Insoilsandmanynaturalwatersthereareavarietyoforganicandinorganicsubstancescapableofundergoingoxidation–reductionreactions.Someofthemareveryliabletooxidationwhenincontactwithair.Inordertocharacterizethembyvoltammetricmethodsitisessen-tialtokeeptheminaclosedsystem.Also,thewholeprocessofmeasurementshouldbecarriedoutwithinashorttime.Sometimesakineticstudyontheiroxida-tion–reductionreactionsisrequired.Thispaperreportsamethodforinsituauto-renewalofthesurfaceofGCelectrodetomeettheseneeds.
2.Experimental2.1.ChemicalsandinstrumentationStandardFe(II)solutionswerepreparedbydissolv-ingspectroscopicallypureironwire(RdHLaborchmi-kahienGmbH&Co.KG.)in3.0MHCl.Otherchemicalsincludedhydrochloricacid(G.R.,NanjingChemicalFactory),potassiumchloride(G.R.,Shu-anghuanChemicalFactory,Beijing),and2,20-bipyridyl