(5.6)-4.6工作曲线法测定水中镁

4.6Workingcurvemethodfordeterminationoftracemagnesiuminwater.

Atomicabsorptionspectrometrymoduleof

AccordingtothelawoflightabsorptionA=KbC=K′C

Formula:A--atomicabsorptionabsorbance;K--constant；b--OpticalpathlengthC--ConcentrationofelementstobemeasuredinC-testsolution.

TheabsorbanceAhasalinearrelationshipwiththeconcentrationCofthetestsolution,andtheconcentrationoftheelementtobemeasuredisobtainedbymeasuringtheabsorbanceofthetestsolution.

PrincipleofStatutoryQuantityofWorkingCurve1

Thedrawingoftheworkingcurveandthemeasurementofsampleconcentration:prepareasetofstandardsolutionscontainingdifferentconcentrationsofelements,andmeasuretheabsorbancevaluesbyorderofconcentrationfromlowtohigh.Thecalibrationcurveofabsorbancetoconcentrationisdrawn.Theabsorbanceofthesamplewasmeasuredunderthesameconditionsasthestandardseries,andthecontentoftheelementisobtainedbyinterpolationfromthecalibrationcurve.workcurve

PrincipleofStatutoryQuantityofWorkingCurve2AbsorptionvalueofelementstobemeasuredConcentrationofelementstobemeasured

Accordingtotheprincipleofworkingcurvemethod,determinationofmagnesiuminwaterincludesthefollowingcontents:

Preparationofstandardseries;

Preparationofsamplesolution;Start-uppreheating,andsettingtheinstrumentconditions;

Measurementoftheabsorbanceofthestandardseriesandsamplesolution;

Drawingworkcurve;Usinginterpolationtomeasuretheconcentrationofthetestsolution.

PracticaltrainingcontentAtomicAbsorptionSpectrophotometer;(ModelTAS990,BeijingGeneralInstrumentsCompany)Aircompressor;Acetylenecylinder;Magnesiumhollowcathodelamp;Glassmeasuringdevicesandcontainers:two100mL-volumetricbottle;five50mLvolumetricbottle;one5mLandone10mLpipette;one100mLbeaker.

ApparatusMagnesiumstandardreservesolution:accuratelyweighing800℃toburntoconstantweightmagnesiumoxide(A.R.)1.6583g,dropping1molL-1HCluntilit’scompletelydissolved,thenmovingitinto1000mLvolumetricflask,dilutingtostandardline,andshakingwell.Theconcentrationofmagnesiuminthissolutionisρ（Mg)=1.000mgmL-1andit’sthestorageperiodis1year.。Secondarydistilledwater；Hydrochloricacid(G.R)Magnesium-containingwaterspecimens.标准贮备液ρMg=1.000mgmL-1

Reagent

Solutionformulation(referencescheme)1.Preparationofstandardworkingliquidrhoρ(Mg)＝100μg/mL2.Preparationofstandardworkingliquidrhoρ(Mg)＝500μg/mL3.Preparestandardseriessolutionρ

(Mg)=0.100,0.200,0.300,0.400,0.500μg/mL4.preparesamplesolution:Absorbing10mLofsamplesolution,andfixthevolumeto100mLSetthefollowingexperimentalconditionsAnalysisline：285.2nm;Spectralpassband：0.4nm;

ExperimentalconditionsHollowcathodelampcurrent:2mA;Acetyleneflowrate:2000mL/min;Burnerheight:5mm.

AnalysismethodsettingSelect"StandardCurve"incorrectionmethodSelectthenameofconcentrationunitsampleNextNextCompletionSamplemeasurementinterfaceEnterthe“SampleSettingsWizard”InputstandardseriesInputthenumberofsamplenamesReturntosamplemeasurementinterfaceClickonthe“sample”Drawtheworkingcurveandchecktheconcentrationofthetestsolutionfromtheworkingcurve.Theconcentrationfoundontheworkingcurveisthedilutedconcentration.Thedilutionprocessis5.00mL→50mL.

Calculationformula:

ρ（Mg）=CV0/V1

Intheformula:ρ(Mg)Magnesiumcontentinthewatersample,μg/mL;Cthevaluefromtheworkingcurve,μg/mL;V0samplesolutionconstantvolume,mL;V1Samplingquantity,mL.

ResultcalculationFactorsaffectingtheaccuracyofmeasurementbyworkingcurve:

Preparationofstandardseriesandsamplesolution(properuseofpipetteandvolumetricbottle);

Measurementconditionsetting;

Thepositionofthecapillaryintheinhalationorsprayingofsolution;

Effectofairconvectionontheflame;

Thetimewhenthereadingbegins.

Thesystemshouldbecalibratedwithstandardsolutionbeforeeachanalysis.Theoperatingconditionsremainunchangedthroughouttheanalysis;

Thecompositionofthestandardseriesandtheanalyzedsamplesolutionshouldbeasconsistentaspossible;

Theabsorbanceofthestandardandsamplesolutionshallbebetween0.2and0.8

Whenthesampleisnotclearorcomplex,andtheanalysiserrorislarge,othermethodsareavailableforquantification.

SummaryofpracticaltrainingThecharacteristicoftheworkingcurvemethod:simpleandfast,suitablefortheanalysisoflarge-scalesampleswithsimplecomposition.Notes:Thestandardsolutionshouldbesimilartothematrixofthetestsolutiontoeliminatethematrixeffect.Appropriateconcentration:Theconcentrationrangeofthestandardsolutionshouldincludetheconcentrationoftheelementtobemeasuredinthetestsolution.Therangeofconcentrationshallbedeterminedbyobtaininganappropriateabsorbancereading(0.2-0.8);Inthemeasurementprocess,thezerodriftshouldbecorrectedbyinhalingdeionizedwaterorblanksolution.Becausetheslopeoftheworkingcurvechangesduetothechangeoftheflowrateofgasandcombustion-supportinggas,theworkingcurveshouldberedrawnforeachanalysis.

Summary-methods,features,andnotesThestandardsolutioncanselecthighlypurely(99.99%)metalwires,rodsandsheetstobetested,whichcanbecleanedwithdiluteacidtoremovethesurfaceoxidelayerorusethesaltsofeachelement.Solubleintheappropriatesolvent,thepreparationofaconcentrationof1mg•mL-1standardreservesolution,thepreparationofgeneraltomaintainacertainacidity(canuse1%dilutenitricacidorhydrochloricacid),soasnottoadsorbthesurfa