英文实验报告模板

Lab11Determinationofheavymetalsinsoilbyatomicabsorptionspectrometry(AAS)Name:XuFeiGroup:The3rdgroupDate:Sep.20th2012Part1Theintroduction1.1Thepurposes(1)Learnhowtooperatetheatomicabsorptionspectrometry;(2)Learnhowtodothepretreatmentofsoilsamples;(3)Getfamiliarwiththeapplicationofatomicabsorptionspectrometry.1.2TheprinciplesAtomicAbsorptionSpectrometry(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.Lab12Part2ThematerialsandapparatusAtomicabsorptionspectrometry;Cuhollowcathodelamp;ACvoltagestabilizer;oil-freegascompressor;acetylenecylinder;oscillator;sampleboat;Erlenmeyerflaskwithstopper(100ml);beaker;graduatecylinder;pipette.Part3Theprocedure3.1operatingprocedureforAAS(1)inspectmajorcomponentstoensureoperatingnormal.(2)Installrequiredhollowcathodelamp.Select“T”beforeturningtothepowerandhollowcathodelamp.Thenselectappropriatelampcurrentandpreheatfor30min.(3)Makesureelectricalmetertopointtozeroandthenturnonhigh-voltagepower.(4)Selectappropriateslitwidth.(5)Rotatemonochromatorandselectrequiredwavelength.Ifthepowermeteristoohighorlow,adjustnegativehighvoltageuntilthemeterreadsfullscale.(6)Adjustlightpointandwavelengthsothatthemeterrepresentsthemaximumvalue.(7)Turnonaircompressorandacetylenegasandigniteflame.Adjusttheflameappropriatelyandpreheattheburner.(8)Injectdistilledwaterintotheflameandcontinuetopreheattheburner.Injectdistilledwaterintotheflameaftereachsample.(9)Select“E”,injectblanksolutionintotheflameandadjustthemetertozero.(10)Optimizeanalysisconditionsandmeasurestandardsolutionandsamples.(11)Aftercompletionofmeasurement,turnoffacetylenegasvalveandthenaircompressor,cutoffgassupplyamomentlater.(12)Select“T”beforeturningoffhighvoltagepower,decreaselampcurrentandthenturnoffthelamp.Atthesametime,allbuttonsshouldbeonoriginalpositions.(13)Checktheequipmentbeforeleavingthelaboratory.3.2Determinationofsoilsamples(1)Preparationofextractingsolution(0.05mol/lEDTAsolution)18.6gofEDTAisdissolvedwithwaterinabeaker(500ml).ThePHisadjustedto7.0usingdiluteammonia.Themixtureistransferredintoavolumetricflask(1000ml),dilutetothemarkandmixedwell.(2)Treatmentofsoilsamples2.50gofair-driedsoil(60-100mesh)isputintoanErlenmeyerflaskwithstopper(100ml).12.5mlofEDTAsolutionisadded.Themixtureisshakenfor1handthenfiltered.Thefiltrateispreservedforanalysis.(3)PreparationofCustandardstocksolution0.10gofCuisdissolvedin15mlof(1:1)nitricacidsolution.Themixtureistransferredintoavolumetricflask(1000ml)anddilutedtothemarkwithre-distilledwater.Theconcentrationofthestockstandardsolutionis100g/ml.(TheconcentrationshouldbecalculatedaccordingtothemassofCu).TheworkingCustandardsolution(10µg/ml)isobtainedbydiluting10mlofCustandardstocksolutionto100mlwithLab13re-distilledwater.(4)Plottingofthestandardcurve0ml,1ml,2ml,3ml,4mland5mlofCustandardsolution(10µg/ml)areaddedrespectivelyto6volumetricflask(10ml)with1mlof5mol/lhydrochloricacid.Themixtureisdilutedwithre-distilledwaterandmixedwelltogive0µg/ml,1.00µg/ml,2.00µg/ml,3.00µg/ml,4.00µg/ml,5.00µg/mlofCu,respectively.Theabsorbanceismeasuredatwavelengthsof3247Å.Thestandardcurveisconstructedbyplottingabsorbancevs.concentration.(5)DeterminationofsamplesThesamplesolutionisanalyzedusingthesameprocedureandconditionsasforthestandardcurve.TheconcentrationofCuisobtainedfromthestandardcurvebasedontheabsorbance.Part4Theresults4.1Therawdatablank12345Abs0.00150.04720.09120.13780.18260.2233Concentration(µg/ml)0.01.02.03.04.05.04.2AASstandardcurveAASstanda