关于英语实验报告

关于英语实验报告关于英语实验报告Determinationofheavymetalsinsoilbyatomicabsorptionspectrometry(AAS)Name:XuFeiGroup:The3rdgroupDate:Sep.20th20xxTheintroductionThepurposes(1)Learnhowtooperatetheatomicabsorptionspectrometry;(2)Learnhowtodothepretreatmentofsoilsamples;(3)Getfamiliarwiththeapplicationofatomicabsorptionspectrometry.TheprinciplesAtomicAbsorptionSpectrometry(AAS)isatechniqueformeasuringquantitiesofchemicalelementspresentinenvironmentalsamplesbymeasuringtheabsorbedradiationbythechemicalelementofinterest.Thisisdonebyreadingthespectraproducedwhenthesampleisexcitedbyradiation.Theatomsabsorbultravioletorvisiblelightandmaketransitionstohigherenergylevels.Atomicabsorptionmethodsmeasuretheamountofenergyintheformofphotonsoflightthatareabsorbedbythesample.Adetectormeasuresthewavelengthsoflighttransmittedbythesample,andcomparesthemtothewavelengthswhichoriginallypassedthroughthesample.Asignalprocessorthenintegratesthechangesinwavelengthabsorbed,whichappearinthereadoutaspeaksofenergyabsorptionatdiscretewavelengths.Theenergyrequiredforanelectrontoleaveanatomisknownasionizationenergyandisspecifictoeachchemicalelement.Whenanelectronmovesfromoneenergyleveltoanotherwithintheatom,aphotonisemittedwithenergyE.Atomsofanelementemitacharacteristicspectralline.Everyatomhasitsowndistinctpatternofwavelengthsatwhichitwillabsorbenergy,duetotheuniqueconfigurationofelectronsinitsoutershell.Thisenablesthequalitativeanalysisofasample.TheconcentrationiscalculatedbasedontheBeer-Lambertlaw.Absorbanceisdirectlyproportionaltotheconcentrationoftheanalyteabsorbedfortheexistingsetofconditions.Theconcentrationisusuallydeterminedfromacalibrationcurve,obtainedusingstandardsofknownconcentration.CalibrationCurveMethod:Preparestandardsolutionsofatleastthreedifferentconcentrations,measuretheabsorbanceofthesestandardsolutions,andprepareacalibrationcurvefromthevaluesobtained.Thenmeasuretheabsorbanceofthetestsolutionadjustedinconcentrationtoameasurablerange,anddeterminetheconcentrationoftheelementfromthecalibrationcurve.ThematerialsandapparatusAtomicabsorptionspectrometry;Cuhollowcathodelamp;ACvoltagestabilizer;oil-freegascompressor;acetylenecylinder;oscillator;sampleboat;Erlenmeyerflaskwithstopper(100ml);beaker;graduatecylinder;pipette.TheprocedureoperatingprocedureforAASinspectmajorcomponentstoensureoperatingnormal.Installrequiredhollowcathodelamp.Select“T”beforeturningtothepowerandhollowcathodelamp.Thenselectappropriatelampcurrentandpreheatfor30min.Makesureelectricalmetertopointtozeroandthenturnonhigh-voltagepower.Selectappropriateslitwidth.Rotatemonochromatorandselectrequiredwavelength.Ifthepowermeteristoohighorlow,adjustnegativehighvoltageuntilthemeterreadsfullscale.Adjustlightpointandwavelengthsothatthemeterrepresentsthemaximumvalue.Turnonaircompressorandacetylenegasandigniteflame.Adjusttheflameappropriatelyandpreheattheburner.Injectdistilledwaterintotheflameandcontinuetopreheattheburner.Injectdistilledwaterintotheflameaftereachsample.Select“E”,injectblanksolutionintotheflameandadjustthemetertozero.Optimizeanalysisconditionsandmeasurestandardsolutionandsamples.Aftercompletionofmeasurement,turnoffacetylenegasvalveandthenaircompressor,cutoffgassupplyamomentlater.Select“T”beforeturningoffhighvoltagepower,decreaselampcurrentandthenturnoffthelamp.Atthesametime,allbuttonsshouldbeonoriginalpositions.Checktheequipmentbeforeleavingthelaboratory.DeterminationofsoilsamplesPreparationofextractingsolution(0.05mol/lEDTAsolution)18.6gofEDTAisdissolvedwithwaterinabeaker(500ml).ThePHisadjustedto7.0usingdiluteammonia.Themixtureistransferredintoavolumetricflask(1000ml),dilutetothemarkandmixedwell.Treatmentofsoilsamples2.50gofair-driedsoil(60-100mesh)isputintoanErlenmeyerflaskwithstopper(100ml).12.5mlofEDTAsolutionisadded.Themixtureisshakenfor1handthenfiltered.Thefiltrateispreservedforanalysis.PreparationofCustandardstocksolution0.10gofCuisdissolvedin15mlof(1:1)nitricacidsolution.Themixtureistransferredintoavolumetricflask(1000ml)anddilutedtothemarkwithre-distilledwater.Theconcentrationofthestockstandardsolutionis100g/ml.(TheconcentrationshouldbecalculatedaccordingtothemassofCu).TheworkingCustandardsolution(10以g/ml)isobtainedbydiluting10mlofCustandardstocksolutionto100mlwithre-distilledwater.Plottingofthestandardcurve0ml,1ml,2ml,3ml,4mland5mlofCustandardsolution(10以g/ml)areaddedrespectivelyto6volumetricflask(10ml)with1mlof5mol/lhydrochloricacid.Themixtureisdilutedwithre-distilledwaterandmixedwelltogive0以g/ml,1.00以g/ml,2.00以g/ml,3.00以g/ml,4.00以g/ml,5.00以g/mlofCu,respectively.Theabsorbanceismeasuredatwavelengthsof3247?.Thestandardcurveisconstructedbyplottingabsorbancevs.concentration.DeterminationofsamplesThesamplesolutionisanalyzedusingthesameprocedureandconditionsasforthestandardcurve.TheconcentrationofCuisobtainedfromthestandardcurvebasedontheabsorbance.TheresultsTherawdataAASstandardcurveCalculationTheabsorbanceofsampleis0.0511.Accordingtotheformulaabove:y=0.0446x+0.0024,R2=0.9997TheconcentrationofCuinthesampleis:1.091mg/L.DiscussionInthisexperiment,weusetheAAStodetermineCuinsoil.IlearnhowtooperatetheAASandthelimitation.Intheexperimentalprocess,standardsolutionwaspreparedinstrictaccordancewiththeexperimentalrequirementsandIlearnhowtodealwiththedata.Finallywegetthestandardcurve,then,thesampleconcentrationiscalculatedaccordingtotheabsorbanceofthesample.Intheexperimentwehaveninemembersinourgroup,sowecandoourbestineveryworkweneedtodo.Formywork,Iamresponsibleforthepreparationofsolutionandtitration.What’smore,IlearnhowtouseandoperatetheAASonthecomputerlater.Ultimately,wegetthelinearformulaisy=0.0446x+0.0024andR2=0.9997.FromAccordingtotheformulaandtheabsorbanceofCuinthesampleis