INSTRUMENTALANALYSIS

儀器分析英文專家講座第1頁Chapter1.IntroductionAnalyticalChemistry:determiningthechemicalcompositionofsamplesofmatter.Qualitativeanalysis:identifyoffunctionalgroups,oratomic,molecularstructureofanalyte(what?)Quantitativeanalysis:amountofanalyte(howmuch?)儀器分析英文專家講座第2頁1.1Classicalmethods(Chemicalanalysis)Qualitativeanalysis:AnalytesProductsrecognizedyieldtreatedwithreagentsColorsBoiling(melting)pointsSolubilitiesOdorsOpticalactivitiesRefractiveindexesQuantitativeanalysis:gravimetric;titrimetric§1.Classificationofanalyticalmethods儀器分析英文專家講座第3頁1.2Instrumentalmethods(Instrumentalanalysis)Earlyin20thcenturyMeasurementsofphysical(chemical)propertiesofanalytes:

-conductivity;electrodepotential;lightabsorption(emission);mass-to-chargeratio;fluorescenceHighlyefficientchromatographicandelectrophoretictechniquesreplacedDistillation,extraction,precipitationa.Developmentofinstrumentsandcomputerb.Developmentofseparationmethodsc.classificationofinstrumentalanalysisOpticalAnalysis(spectrometry);ElectrochemicalAnalysis;Chromatography……………儀器分析英文專家講座第4頁§2typesofinstrumentalmethodsChemical(physical)characteristicsEmissionofradiationAbsorptionofradiationScatteringofradiationDiffractionofradiationRotationofradiationElectricalpotential

ElectricalchargeElectricalcurrentElectricalresistanceMassMass-to-chargeratioRateofreactionThermalcharacteristicsRadioactivityInstrumentalmethodsEmissionspectroscopy,fluorescence,phosphorescence,luminescenceAbsorptionspectroscopyRamanspectroscopyX-RaydiffractionCirculardichroismPotentiometry,chronopotentiometryCoulometryAmperometry,polarographyConductometryQuartzcrystalmicrobalanceMassspectrometryKineticmethodsThermalgravimetryandtitrimetryActivationandisotopedilutionmethods儀器分析英文專家講座第5頁§3InstrumentsforanalysismanipulatedandinterpretedbyhumanOverallprocessofinstrumentalmeasurementDatadomain:

wayofencodinganalyticalresponseinelectricalornonelectricalsignals(namelyelectricaldomainsandnonelectricaldomains)Detector(general):devicethatindicateschangeinenvironmentTransducer(specific):devicethatconvertsnon-electricaltoelectricaldataSensor(specific):devicethatconvertschemicaltoelectricaldata儀器分析英文專家講座第6頁AnalogdomainsTimedomainsDigitaldomainsAnalog-continuouslyvariablemagnitude(current,voltage,charge)Time-varywithtime(frequency,phase,pulsewidth)Digital

-discretevalues(count,serial,parallel,number*)儀器分析英文專家講座第7頁Table1-2Examplesofinstrumentcomponents(p.4)儀器分析英文專家講座第8頁§4SelectingananalyticalmethodWhataccuracyisrequired?------------------------Accuracy/BiasHowmuchsampleisavailable?-------------------sensitivityWhatistheconcentrationrangeoftheanalyte?---DynamicrangeWhatcomponentsoftheamplewillcauseinterference?------------SelectivityWhatarethephysicalandchemicalpropertiesofthesamplematrix?------analyticalmethodsHowmanysamplesaretobeanalyzed?---------economicstandpointDefiningtheproblem:儀器分析英文專家講座第9頁Performancecharacteristicsofinstruments(Figuresofmerit)CriterionFigureofmerit1.PrecisionAbsolutestandarddeviation,relativestandarddeviation,coefficientofvariation,variance2.Bias(accuracy)Absolutesystematicerror,relativesystematicerror3.SensitivityCalibrationsensitivity,analyticalsensitivity4.DetectionlimitBlankplusthreetimesstandarddeviationofablank5.ConcentrationrangeConcentrationlimitofquantitation(LOD)toconcentrationlimitoflinearity(LOL)6.SelectivityCoefficientofselectivity儀器分析英文專家講座第10頁Precision:thedegreeofmutualagreementamongdatathathavebeenobtainedinthesameway.儀器分析英文專家講座第11頁Threetypesofsucherrors:Instrumental:somethingwrongwiththeinstrument(batterieslow,temperatureeffectsthecircuitry,calibrationerrors,etc.)Personal:judgmenterrors,readingthemeterfromthewrongangle,lackofcarefultechnique.Method:oftenaresultofnon-idealchemicalbehaviour;slowreactions,contaminants,instabilityofreagents,lossofanalytebyadsorption.Mustuseguaranteedstandards.儀器分析英文專家講座第12頁Precisionandaccuracy

儀器分析英文專家講座第13頁Sensitivity:ameasureoftheabilityofaninstrument(method)todiscriminatebetweentwosmalldifferencesinanalyteconcentrationCalibrationsensitivity:theslopeofthecalibrationcurveattheconcentrationofinterestCalibrationcurveSignal(s)s0S=mC+Sblconcentration儀器分析英文專家講座第14頁Analyticalsensitivity:includeprecisioninameanongfulmathematicalstatementofsensitivity=m/ssCalibrationsensitivityStandarddeviationofmeasurement儀器分析英文專家講座第15頁Detectionlimit(檢出限):theminimumconcentration(mass)ofanalytethatcanbedetectedataknownconfidencelevel.Sm=Sbl+ksMinimumdistinguishableanalyticalsignalMeanblanksignalStandarddeviationonblanksignalUsuallytakentobe3?Dependsuponsignal/noiseratio.?Analysissignalmustbelargerthanblanksignal.Howmuchlarger?(at95%confidencelevel)Cm=(Sm-Sbl)/mS=mC+Sbl儀器分析英文專家講座第16頁Example1：ConcentrationSignalNETSignal0ppm(blank)0.1360.00010.ppm0.7210.5851.0ppm0.1950.0590.10ppm0.1420.0060.010ppm0.1370.001S=3σblank=3(0.002)=0.006Sm=Sblank+S=0.136+0.006=0.142(0.10ppmPb)Supposethat:σblank=0.002儀器分析英文專家講座第17頁Example2：

AfluorescencemethodwasappliedtodeterminecomponentAinthesolution.Theresultsareshowninthetable.SupposethattheSDofblankis0.352.Anunknownsamplegiveresultsof525,536and529.Pleasecalculate:1.Thesensitivityandthedetectionlimitofthemethod.2.TheconcentrationofAinthesample,standarddeviationandrelativestandarddeviationofthedetection.儀器分析英文專家講座第18頁Letusmaketheworkingcurve(I~c)firstI=0.834+109c

Relativecoefficient:r=0.99998

Sensitivity:109ml/μgDetectionlimit:CDL=(IDL–I0)/m=3×0.352/（109ml/μg） =0.00969μg/ml

I0=0.834IDL=I0+3SD=0.834+109cDL

儀器分析英文專家講座第19頁I=(526+536+529)/3=530ConcentrationofAinthesample:c=(530-0.834)/109=4.85μg/ml

standarddeviations=5.57

relativestandarddeviation:RSD=5.57/530×100%=1.05%

儀器分析英文專家講座第20頁LimitofQuantitation

（LOQ檢測限）Sq=S0+10sThedetectionlimitanswersthequestion“Isthisanalytepresentornot?”However,toactuallyanswerthequestion“Howmuchoftheanalyteispresent?”requiresastilllargersignal.ThewidelyacceptedlevelatwhichtheanalytecanbequantifiedisTENtimesthestandarddeviation.(DetectionisTHREEtimes.)儀器分析英文專家講座第21頁SignalRelationshipsMeasuredSignalLevel0MeanBackgroundSignalLevelDistributionofblankmeasurementsDetectionLimit3sblQuantitationLimit10sbl儀器分析英文專家講座第22頁Dynamicrange:concentrationrangebetweenLOQandLOL儀器分析英文專家講座第23頁Selectivity:thedegreethatthemethodis“free”fromreferencebyotherspeciescontainedinthesamplematrix.Noanalyticalmethodiscompletelyfreefrominterferencebyconcomitants.Bestmethodismoresensitivetoanalytethaninterferingspecies(interferent).儀器分析英文專家講座第24頁Example3(p.15):Theselectivitycoefficientforanion-selectiveelectrode(ISE)forK+withrespecttoNa+isreportedtobe0.052.CalculatetherelativeerrorinthedeterminationofK+inasolutionthathasaK+concentrationof3.00×10-2MiftheNa+concentrationis(a)2.00×10-2M;(b)2.00×10-3M;(c)2.00×10-4M.AssumethatSblforaseriesofblankwasapproximatelyzero.儀器分析英文專家講座第25頁Solution:(a)SincekNa+,K+=0.052,Sbl=0,cK+=3.00×10-2M,cNa+=3.00×10-2MthenS=mK+(cK++kNa+,K+cNa+)+0=4.04×10-3mK+

IfNa+werenotpresent,thenS0=mK+(cK++kNa+,K+cNa+)+0=3.00×10-3mK+Erel=(S-S0)/S0=35%;Similarly,weget(b)Erel=(S-S0)/S0=3.5%(c)Erel=(S-S0)/S0=0.35%儀器分析英文專家講座第26頁§5Calibrationofinstrumentalmethods5.1calibrationcurves(workingcurves;analyticalcurves;standardcurves)Ourfamiliarmethod…Unfortunately,matchingthematrixofcomplexsamplesisoftendifficultorimpossible.Twomethodstominimizethematrixeffects:Separatingtheanalytefrominterferencepriortomeasurements;Employingstandardadditionalmethods儀器分析英文專家講座第27頁5.2standardadditionmethodsAdding(spiking)oneormoreincrementsofastandardsolutiontosamplealiquotsofthesamesiz