The ferrozine method revisited--Fe(II) or Fe(III) determinat

铁含量测定

AppliedGeochemistry15(2000)785±790

Theferrozinemethodrevisited:Fe(II)/Fe(III)determination

innaturalwaters

E.Viollier*,P.W.Inglett1,K.Hunter,A.N.Roychoudhury,P.VanCappellen

GeorgiaInstituteofTechnology,SchoolofEarthandAtmosphericSciences,Atlanta,GA30332-0340,USA

Received4October1998;receivedinrevisedform31July1999

EditorialhandlingbyR.Raiswell

Abstract

Theoriginalferrozinemethodhasbeenmodi®edtosequentiallydeterminetheFe(II)/Fe(III)speciationinsmallvolumesoffreshandmarinewatersamples,atthesubmicromolarlevel.SpectrophotometricanalysesoftheFe(II)±ferrozinecomplexareperformedonasinglealiquotbeforeandafterareductionstepwithhydroxylamine.TheprocedureiscalibratedusingFe(III)standardsstableundernormalconditionsofanalysis.ItisshownalsothatthepresenceofhighconcentrationsofdissolvedNOM(naturalorganicmatter)donotcreateanysigni®cantartifacts.ThemethodwasusedtomeasureFe(II)andFe(III)depthdistributioninsaltmarshporewatersandinastrati®edmarinebasin.#2000ElsevierScienceLtd.Allrightsreserved.

Keywords:Ironspeciation;Freshandmarinewater;Spectrophotometry;Ferrozine

1.Introduction

Determinationoftheconcentrationdistributionofsolublereactivespeciesiskeytounderstandingbiogeo-chemicalprocessesinnaturalsettings.Ironisoneofthemostreactiveelementsinaquaticenvironments,anditscyclingiscoupledtothatofthemajorbiogeo-chemicalelements(C,O,SandP)andtraceelementssuchasheavymetals(TessierandCampbell,1988).Itispresentinthehydrosphereundertwooxidation

*Correspondingauthor.Presentaddress:LaboratoiredeochimiedesEaux,UniversiteParis7,2PlaceJussieu,Ge

75251Pariscedex05,France.Fax:+33-1-4427-8148.

E-mailaddress:viollier@ipgp.jussieu.fr(E.Viollier).1

Presentaddress:SoilandWaterScienceDepartment,Uni-versityofFlorida,106NewellHall,Gainesville,FL32611-0570,USA.

states,IIandIII,whicharethermodynamicallystableunderanoxicandoxicconditions,respectively.Fe(III)formscomplexeswithorganicacidsandoxyhydroxidecolloids.Thelattermayaggregateintolargerparticles(Davison,1993).Fe(III)oxyhydroxidesundergoreduc-tivedissolutioninmostaquaticsediments(VanCap-pellenandGaillard,1996).Thereductivedissolutioncanbecoupleddirectlytotheoxidationoforganicmatterbyspecializedbacteria(DiChristinaandDelong,1993),oritmayproceedviaabioticreactionswithinorganicororganicreductants(VanCappellenandWang,1996).

Theusualmethodsforcollectingsedimentporewaters(dialysis,coreextraction,di usiveequilibrationinthin®lms)forthedeterminationofdissolvedchemi-calparameters(Carignan,1984;Janhkeetal.,1986;Davisonetal.,1994)typicallyyieldsmallsamplevolumes(200mlto20ml).ThespectrophotometricmeasurementsofFe(II)andtotalFe(i.e.Fe(II)+-

0883-2927/00/$-seefrontmatter#2000ElsevierScienceLtd.Allrightsreserved.PII:S0883-2927(99)00097-

9

铁含量测定

786E.Viollieretal./AppliedGeochemistry15(2000)785±790

Fe(III)ateactivesamplespecies)fractionsaregenerally(Fadrusperformedontwosepar-metricFe(II)concentrationisandalsoMaly,measured1975).byElectro-volta-terminationmethodsrecently,oftotalcomplementedFe(Bu ebyetanindependentde-detectionElrodetal.(1991)developedal.,a1987).methodMoreofto(aftermeasurebasedwaterreductionsubnanomolarontheworkofYamadaetal.(1985)toFe(II)withlevelsascorbicofFe(II)acid)andinFe(III)minescenceby¯owapproachesofisdetector.injectionanalysis,coupledtoachemilu-oceantherequirementAmajorfordrawbackaseparateofanalysisthesecalculateddissolvedbyFe(II)di erence).

andtotaldissolvedFe(Fe(III)issamplesTheconcentrationsare(0.45mmporeoftotalFemeasuredon®lteredtrationsgenerallyinterpretedsize)asfromrepresentinganoxicenvironmentstheconcen-Christensen,ofsampling1994).Fe(II)However,species(e.g.OAlbrechtensenand2contaminationduringofFe(II)Fe(III)andoxyhydroxides®ltrationmayandinducedecreasefastprecipitationraloccur.waters,concentration.contaminationMoreover,bycolloidalwhencollectingthedissolvednatu-mayincreasecauseThethepreservationdissolutionofofthesesamplesparticles,byparticlesacidi®cationmayandhencetwothetotaldissolvedFeconcentration.Theseneede ectsablyforanimmediatearenotreproduciblespeciationandemphasizethetoTheonauthorsasinglemeasurement,prefer-havesampledesignedfraction.

antoworkwithsamplevolumesofexperimental1mlorlessprotocolFe(III)determineableatthethedissolvedconcentrationsofFe(II)inorderandbancesfor®eldsubmicromolarwork,consistslevel.ofrecordingThemethod,suit-anFe(III)ofanreductionFe(II)step.

coloredcomplexbeforetheandabsor-after2.Theory

dyl)-5,6-diphenyl-1,2,4-triazine-Theferrozine(monosodiumsaltagentpalentproposedbyStookey(1970)p,p'hydrate-disulfonicof3-(2-pyri-whichreactsacid)re-isnmused.Fetoformastablemagentacomplexspecieswith

tionandThecoe cientyields,maximumbetweenabsorbanceclosetopH30,0004andisrecordedat562lmol9,aÀ1molarabsorp-Fe(III)complexisalsopresentinsolutioncmÀ1.Whentrationorascolloidswithdiameters(asalesstruethandissolvedtherebymembranecomplexinterferingporesize)itcanreactwithferrozine,the®l-and(Si ert,1989).withAthemixturecolorationofdissolvedoftheferrouslowingFe(III)absorbance:

reactingwiththeferrozineleadstotheFe(II)fol-A1 eFe II lCFe II eFe III lCFe III 1

whereductionA1coe cients,step,istheemeasuredabsorbancebeforethere-Fe(II)andeFe(III)areClistheopticpathlengthmolarandabsorptionCFe(II)andFe(III)Fe(III)AfterareadditiontheFespeciesofconcentrations.

centrationreducestoFe(II),areducingtherebyagentandabu er,additiveabsorbance:

propertyofFe(II)±ferrozineoftheLambert±Beercomplexincreasinginlawsolution.thecon-yieldsThetheA2 eFe II l CFe II CFe III a

2

whereductionAditionstep2isandthemeasuredabsorbanceafterthere-linearofFe(II)andsystemthereducingaisthedilutionfactorduetoad-Fe(III)ofEqs.concentrations:(1)agentandand(2)bu er.issolvedTheforsimpletheCFe II

A1eFe II laÀA2eFe III lFe II Fe II Fe III 3

…… 此处隐藏：15414字，全部文档内容请下载后查看。喜欢就下载吧 ……