密歇根州立大学-仪器分析-Introduction_to_instrumental_analysis

CEM333InstrumentalAnalysisSimonJ.GarrettRoom:CEM234Phone:[phone]ext208E-mail:[e-mail]:Tuesday,Thursday9:00-9:50amRoom136OfficeHours:Tuesdays10:00-11:00amCEM333page1.1CourseObjectivesTeachfundamentalsofinstrumentalanalysisLecture:Discusstheoryandbackgroundfor(1)chemical/physicalpropertymeasured(2)originofchemical/physicalproperty(3)instrumentdesignandnatureofresponse(4)signalprocessingandrelationshipbetweenreadouttopropertymeasuredLaboratory:Provideshands-onexperiencein(1)relatinglecturematerialtopracticalanalysis(2)designandoperationofarealinstrument(3)measurementsonrangeofinstruments(4)exampleanalysestoillustratevalueoftechniqueCEM333page1.2Introduction(Chapter1)ClassificationofAnalyticalMethodsQualitativeinstrumentalanalysisisthatmeasuredpropertyindicatespresenceofanalyteinmatrixQuantitativeinstrumentalanalysisisthatmagnitudeofmeasuredpropertyisproportionaltoconcentrationofanalyteinmatrixSpeciesofinterestAllconstituentsincludinganalyte.Matrix-analyte=concomitantsOftenneedpretreatment-chemicalextraction,distillation,separation,precipitation(A)Classical:Qualitative-identificationbycolor,indicators,boilingpoints,odorsQuantitative-massorvolume(e.g.gravimetric,volumetric)(B)Instrumental:Qualitative-chromatography,electrophoresisandidentificationbymeasuringphysicalproperty(e.g.spectroscopy,electrodepotential)Quantitative-measuringpropertyanddeterminingrelationshiptoconcentration(e.g.spectrophotometry,massspectrometry)Often,sameinstrumentalmethodusedforqualitativeandquantitativeanalysisCEM333page1.3TypesofInstrumentalMethods:PropertyExampleMethodRadiationemissionEmissionspectroscopy-fluorescence,phosphorescence,luminescenceRadiationabsorptionAbsorptionspectroscopy-spectrophotometry,photometry,nuclearmagneticresonance,electronspinresonanceRadiationscatteringTurbidity,RamanRadiationrefractionRefractometry,interferometryRadiationdiffractionX-ray,electronRadiationrotationPolarimetry,circulardichroismElectricalpotentialPotentiometryElectricalchargeCoulometryElectricalcurrentVoltammetry-amperometry,polarographyElectricalresistanceConductometryMassGravimetryMass-to-chargeratioMassspectrometryRateofreactionStoppedflow,flowinjectionanalysisThermalThermalgravimetry,calorimetryRadioactivityActivation,isotopedilution(Oftencombinedwithchromatographicorelectrophoreticmethods)CEM333page1.4StimulusResponseAnalyte(inmatrix)EnergyAnalyticalDataencodedinformationExample:SpectrophotometryInstrument:spectrophotometerStimulus:monochromaticlightenergyAnalyticalresponse:lightabsorptionTransducer:photocellData:electricalcurrentDataprocessor:currentmeterReadout:meterscaleDataDomains:wayofencodinganalyticalresponseinelectricalornon-electricalsignals.Interdomainconversionstransforminformationfromonedomaintoanother.LightIntensityPhotocell─→────CurrentCurrentMeter─→─────ScaleDetector(general):devicethatindicateschangeinenvironmentTransducer(specific):devicethatconvertsnon-electricaltoelectricaldataSensor(specific):devicethatconvertschemicaltoelectricaldataCEM333page1.5Non-ElectricalDomainsElectricalDomainsPhysical(lightintensity,color)CurrentChemical(pH)VoltageScalePosition(length)ChargeNumber(objects)FrequencyPulsewidthPhaseCountSerialParallelTime-varywithtime(frequency,phase,pulsewidth)Analog-continuouslyvariablemagnitude(current,voltage,charge)Digital-discretevalues(count,serial,parallel,number*)CEM333page1.6DigitalBinaryDataAdvantages(1)easytostore(2)notsusceptibletonoise221stbit2ndbit3rdbit4thbitHiLoCountSerial2021202122ParallelHiLoHiLoHiLoHiLo3separatesignals20=1,21=2,22=4...CEM333page1.7PerformanceCharacteristics:FiguresofMeritHowtochooseananalyticalmethod?Howgoodismeasurement?Howreproducible?-PrecisionHowclosetotruevalue?-Accuracy/BiasHowsmalladifferencecanbemeasured?-SensitivityWhatrangeofamounts?-DynamicRangeHowmuchinterference?-SelectivityCEM333page1.8Precision-IndeterminateorrandomerrorsAbsolutestandarddeviation:s=xi-x()2i-0i=N∑N-1Variance:s2Relativestandarddeviation:RSD=sxStandarddeviationofmean:sm=sNAccuracy-Determinateerrors(operator,method,instrumental)Bias:bias=x-xtrueSensitivityCalibrationsensitivity:S=dSignaldcc+Signalblank=mc+Signalblank(largerslopeofcalibrationcurvem,moresensitivemeasurement)DetectionLimitSignalmustbebiggerthanrandomnoiseofblankMinimumsignal:Signalmin=Av.Signalblank+ksblankFromstatisticsk=3ormore(at95%confidencelevel)CEM333page1.9DynamicRangeAtdetectionlimitwecansayconfidentlyanalyteispresentbutcannotperformreliablequantitationLevelofquantitation(LOQ):k=10Limitoflinearity(LOL):whensignalisnolongerproportionaltoconcentrationDynamicrange:LOLLOQ102to106Selectivity:Noanalyticalmethodiscompletelyfreefrominterferencebyconcomitants.Bestmethodismoresensitivetoanalytethaninterferingspecies(interferent).MatrixwithspeciesA&B:Signal=mAcA+mBcB+SignalblankSelectivitycoefficient:kB,A=mBmAk'svarybetween0(noselectivity)andlargenumber(veryselective).CEM333page1.10CalibrationmethodsBasisofquantitativeanalysisismagnitudeofmeasuredpropertyisproportionaltoconcentrationofanalyteSignal∝[x]orSignal=m[x]+Signa