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1、在比较中学习,培养分析问题和总结问题的能力,掌握在比较中学习,培养分析问题和总结问题的能力,掌握常用仪器分析方法原理、应用,熟悉仪器结构常用仪器分析方法原理、应用,熟悉仪器结构理解和记忆相结合理解和记忆相结合查阅文献资料,参加科学讲座,培养创新精神查阅文献资料,参加科学讲座,培养创新精神了解各仪器的仪器厂商,并对每种仪器的型号做对比了解各仪器的仪器厂商,并对每种仪器的型号做对比平时成绩平时成绩40%,包括作业、考勤、提问以及文献报告等,包括作业、考勤、提问以及文献报告等期末考试成绩期末考试成绩60% 1.5 HOW to study this http:/pubs.acs.orghttp:/中
2、国色谱网中国仪器信息网中国期刊网仪器厂商AgilentWaters Micromass Thermo http:/ http:/ 2 Electrochemistry 1 Introduction to electrochemistryAnodereaction:Red=Ox+ne-(1)Cathodereaction:Ox+ne-=Red(2)1.1OxidationreductionreactionCellreactionexpressionAnode solution,( Ox)solution,( Red) CathodeForexample:Zn ZnSO4,(xMol)CuSO4,
3、(yMol) CuAnode:ZnZn2+2e-(3)Cathode:Cu2+2e-Cu(4)Electrontransferred,thecurrent,thevoltageQ=n F(F=?)w(injoules)=E(involts) q(incoulombs) i=E/R(a) Galvanic and (b) electrolytic cellsForaCell:Ecell=Ecathode-EanodeIf,Ecell0:GalvanicCellEcell0:ElectrolyicCell1.2.Half-cellPotential(1)(2) Standard reduction
4、 potentialE0,thesuperscriptzeromeansthestandardstateconditions.E0,allsolutesare1Mandallgasesare1atm,othersolidsorliquidsarepure.Zn(s) Zn2+(aq,1M) H+(aq,1M) H2(g,1atm) Pt(s) E0cell=E0cathodeE0anode0.76V=0-E0ZnE0Zn=-0.76VSoZn2+2e-Zn(s) E0Zn=-0.76V - -平衡时电极电位(平衡时电极电位(V V) - -标准电极电位标准电极电位 (V V) - -分别为电极
5、反应中氧化态和还原态的活度;分别为电极反应中氧化态和还原态的活度; - -为电极反应中的电子得失数为电极反应中的电子得失数 (3) Nernst equation Ifsomesubstanceiswaterorsolid,itsconcentrationis1;ifitisliquid,itsconcentrationispressure.For example电化学分析的分类方法电化学分析的分类方法 按按IUPACIUPAC的推荐,可分为三类的推荐,可分为三类: :(1)(1)不涉及双电层,也不涉及电极反应。电导分析。不涉及双电层,也不涉及电极反应。电导分析。(2)(2)涉及双电层,但不涉
6、及电极反应。涉及双电层,但不涉及电极反应。(3)(3)涉及电极反应。电解、库仑、极谱、伏安分析等。涉及电极反应。电解、库仑、极谱、伏安分析等。 习惯分类方法(按测量的电化学参数分类)习惯分类方法(按测量的电化学参数分类): :(1)(1)电导分析法:测量电导值;电导分析法:测量电导值;(2)(2)电位分析法:测量电动势;电位分析法:测量电动势;(3)(3)电解电解( (电重量电重量) )分析法:测量电解过程电极上析出物重量;分析法:测量电解过程电极上析出物重量;(4)(4)库仑分析法:测量电解过程中的电量;库仑分析法:测量电解过程中的电量;(5)(5)伏安分析:测量电流与电位变化曲线;伏安分析
7、:测量电流与电位变化曲线;(6)(6)极谱分析:使用滴汞电极时的伏安分析。极谱分析:使用滴汞电极时的伏安分析。(4) ClassificationClassificationofelectroanalyticalmethods These methods rely on the measurement of Ecell for quantification. A number of common reference and indicative electrodes are concerned along with general calculations and analytical app
8、roaches2 Potentionmetric Methods2.1indictorelectrodeResponds to the change in analyte activity.(1)MetallicElectrodes(a) first kind: a metal wire, mesh, or solid strip that responds to its own cation in solution. eg., Cu/Cu2+, Ag/Ag+ poor selectivity, easily oxidized, limited pH ranges(b) second kind
9、: a metal coated with one of its sparingly soluble salts. Responds to the anion of the salt. eg., a silver wire coated with AgCl AgCl(s)+e- Ag(s) + Cl- E=0.222-0.005916logCl-Reference electrode a fixed potential over time and temperature, long term stability, the ability to return to the initial pot
10、ential after exposure to small currents, follow the Nernst equationCalomel electrodeDefinition:Hg、Hg2Cl2 and a known concentration of KCl(0.1, 3.5, 4.6M)Electorde:Hg Hg2Cl2,KCl(xM) Reaction:Hg2Cl2(s) + 2e = 2Hg(l)+ 2Cl- 特点特点:a) 制作简单、应用广泛;制作简单、应用广泛;b) 使用温度较低使用温度较低(H3O+ .This false response is called
11、the alkaline error because a common source of Na+ is from NaOH.Note: the electrode shows no response to OH-.SodiumelectrodeBymodificationoftheglassmembrane,youcanmakeanelectrodethatismoresensitivetoNa+comparedtoH3O+.AciderrorAtpH 59/n(mV), ipa / ipc 1,阴阳峰电流比值越小,则该电极体系越不可逆 Ep = Epa Epc = 2.22RTnF=59
12、n(mV)如对氨基苯酚的电极反应过程: 在第一次阳极扫描时电极附近溶液中只有对氨基苯酚是电活性物质在电极上被氧化生成对亚氨基苯醌。得峰1(E过程):电极反应产物对亚氨基苯醌在电极附近溶液中,与水和氢离子发生化学反应(C过程):再再次阳极扫描时,对苯二酚被氧化为苯醌,形成峰次阳极扫描时,对苯二酚被氧化为苯醌,形成峰4 4。而峰。而峰5 5与峰与峰1 1过程相同,过程相同,即对即对氨基苯酚被氧化为对氨基苯酚被氧化为对亚氨基苯醌。亚氨基苯醌。Fig. Cyclic voltammograms of HRP/Nafion-cysteine/Au in 20mM PBS (pH7.0) at scan
13、rates (from inner to outer) of: 20, 40, 60, 80, 100, 120, 140, 160,180, 200, 220, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850,900, 950 and 1000 mV/s. The inset of figure shows the relationship between peak current (Ip) and scan rate (). () Anodic peak current (Ipa); () cathodic p
14、eak current (Ipc).3-2. Differential Pulse PolarographyExcellent resolution of different electroactive speciesMore sensitive (detection limits 10-7-10-8 M) than conventional DC or current sampled polarographytimeApplied potential20-100mVDrop time1-2 sCurrent measure0.02sVoltage programCurrent-voltage
15、 curveiPulses of 20-100 mV Current is sampled just before and near the end of the pulse, and id is measuredThe result is a derivative plot ( id / E) of a conventional DC current sampled polarogram 3-3 溶出伏安法: 预预电电解解过过程程就就是是根根据据被被测测物物质质的的氧氧化化还还 原原特特性性,在在工工作作电电极极上上加加上上一一恒恒定定电电位位,在在搅搅拌拌溶溶液液的的条条件件下下使使被被测物通过还原或氧化的方式沉积(预富集)在电极上。测物通过还原或氧化的方式沉积(预富集)在电极上。 溶溶出出过过程程是是向向电电极极加加上上一一定定波波形形的的变变化化电电位位,使使沉沉积积物物再再氧氧化化或或还还原原进进入入溶溶液液。若若溶溶出出时时工工作作电电极极上上发发生生氧氧化化反反应应,则则称称为为阳阳极极溶溶出出伏伏安安法法,发发生生还还原原反反应应,则则称称为阴极溶出伏安法。为阴极溶出伏安法。 (沉积过程)沉积过程)(溶出过程)溶出过程)根据溶出过程中阳极电流与离子浓度的线性关系进行定量根据溶出过程中阳极电流与离子浓度的线性关系进行定量