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.20th2012Part1Theintroduction1.1Thepurposes(1)Learnhowtooperatetheatomicabsorptionspectrometry;(2)Learnhowtodothepretreatmentofsoilsamples;(3)Getfamiliarwiththeapplicationofatomicabsorptionspectrometry.1.2TheprinciplesAtomicAbsorptionSpectrometry(AAS)isatechniqueformeasuringquantitiesofchemicalelementspresentinenvironmentalsamplesbymeasuringtheabsorbedradiationbythechemicalelementofinterest.Thisisdonebyreadingthespectraproducedwhenthesampleisexcitedbyradiation.Theatomsabsorbultravioletorvisiblelightandmaketransitionstohigherenergylevels.Atomicabsorptionmethodsmeasuretheamountofenergyintheformtrometry.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.Part2ThematerialsandapparatusAtomicabsorptionspectrometry;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)Injectdistilledwaterintotheflam...