【作者】 刘述梅；

【导师】 黎拒难；

【作者基本信息】 湘潭大学 ， 分析化学， 2003， 硕士

【摘要】 本文利用碳糊电极（CPE）在正电位区测定残余电流低，基线平稳的特点，首次用吸附伏安法研究稀土络合物的氧化峰并分别用来测定中、重稀土，铈和钪，为非电活性金属元素如稀土、钍、锆等的电化学分析提供了新的途径。 全文共分三章。 第一章利用中、重稀土（Ⅲ）-茜素氨羧络合剂（ALC）在CPE上产生的与ALC试剂峰很好分开的氧化峰，建立了吸附伏安法测定中、重稀土的新方法。在0.12 mol／L HAc-NaAc-0.03 mol／L邻苯二甲酸氢钾（pH 5.0）中，-0.2 V（vs.SCE）富集60 s，线性扫描至0.8 V，中、重稀土（Ⅲ）-ALC在碳糊电极上产生灵敏的吸附氧化峰，其二次导数峰电流与中、重稀土浓度有线性关系。重稀土Dy、Ho、Er、Tm、Yb、Lu灵敏度高，在1.0×10^-9～2.0×10^-7mol／L范围内呈线性关系，富集120 s检出限达5.0×10^-10mol／L（S／N=3）。中稀土Sm、Eu、Gd、Tb与Y灵敏度略低，在3.0×10^-9～3.0×10^-7mol／L范围内呈线性关系，富集120 s检出限为2.0×10^-9mol／L（S／N=3）。探讨了电极反应机理。该法用于稀土球墨铸铁样品中稀七（除La、Ce、Pr、Nd、Sc）的测定，结果满意。 第二章研究了铈（Ⅲ）-茜素氨羧络合剂在碳糊电极正电位区的吸附伏安行为，探讨了在其它稀土存在下单独测定铈的最佳条件，建立了一种高灵敏度，高选择性的测定铈的新方法。在0.08 mol／LHAc-NaAc-0.012 mol／L邻苯二甲酸氢钾底液（pH 4.7）中，-0.2 V富集60 s，以100 mV／s的扫速阳极化线性扫描至0.8 V，Ce（Ⅲ）-ALC刘述梅:稀上（111）络合物在碳糊电极上的吸附伏安法研究络合物产生灵敏的吸附氧化峰，该峰与其它斓系元素络合物峰申‘位相差近100 mV，以此可单独测定饰。其二次导数峰电流与饰浓度在6.0火10一，一3.0 K10一7mol/L范围内呈线性关系，富集1205检出限达3.0火10一，m。l/LC夕解3)。电极的重现性好，在同一支电极同一表面上15次连续测定4.0 xlo一smc)l/LCe（HD，相对标准偏差为3.5%。探讨了电极反应机理。该法用于稀土球墨铸铁样品中饰的测定，结果满意。 第三章研究了杭（I11）一茜素氨梭络合剂在碳糊电极正电位区的吸附伏安行为，利用该络合物产生的吸附氧化峰二次导数峰电流与杭浓度成正比测定抗。测定条件为:。.08 mol/L HAc一NaAc一O·02mOI_/L邻苯二甲酸氢钾底液，pH 4 .3，一0 .ZV富集455（或90。;），扫速150 mV/S，一0.ZV至0.SV线性扫描。测定线性范围为2.OX1（）一，一6.0火10一7 mol/L，富集1205检出限达1.0 x10一，mo口L ‘国/解二3）。探讨了电极反应机理。电极的重现性好，在同一支电极同一表面上15次连续测定4.0 x 10一8 mol/L SC（111），相对标准偏差为3.7%。该法用于矿石样品中杭的测定，结果满意。 由上一可‘矢一}，各稀土一茜素氨梭络合剂在CPE正电位区的吸附伏安行为有一很大差异，一可以达到分别测定中、_重稀土，饰，杭的目的。合理设计CPE（如加修饰剂），进一步提高电极的选择性、灵敏度一和抗于扰能力，将是发展方向。更多还原

【Abstract】 Carbon paste electrodes (CPEs) are characteristics of low background currents and flat measure baseline over a range of the large positive potentials in aqueous solution. The paper investigates for the first time oxidation peaks of the complexes of rare earths at a CPE by adsorptive stripping voltammetry, and presents several sensitive procedures for quantifying various rare earth elements based on the adsorptive oxidation peak. A new approach is provided for determination of non-electroactive metals such as rare earths, zirconium, thorium etc.The paper consists of three chapters.The first chapter deals with the adsorption voltammetry for the determination of middle and heavy rare earths in the presence of alizarin complexon (ALC) at a CPE. In a supporting electrolyte of 0.12 mol/L HAc-NaAc and 0.03 mol/L potassium biphthalate (pH5.0), the complexes of middle and heavy rare earths(III) with ALC yield a sensitive adsorptive oxidation peak when linear-scanning at 100mV/s from -0.2 to 0.8 V. The second-order derivative peak currents are proportional to the concentrations of middle and heavy rare earths(III). The sensitivity of the complexes of heavy rare earths(III) (Dy, Ho, Er, Tm, Yb, Lu) is higher than that of middle rare earths(III) (Sm, Eu, Gd, Tb)and Y. For heavy rare earths the detection limit attains 5.0×10-10 mol/L (S/N=3) for a 120 s preconcentration, the linear range is 1.0×10-9 -2.0×10-7 mol/L. For middle rare earths and Y the linear range is 3.0×10-9-3.0×10-7mol/L, and the detection limit is 2.0×10-9 mol/L(S/N=3) for a 120 s preconcentration. The relative standard deviation is 3.8 % for 20 successive determinations of 4.0×10-8 mol/L Ho3+ on the same electrode surface. The electrode processes of the adsorbed complex are investigated. The developed method has been applied to determination of the sum of rare earths (except La, Ce, Pr, Nd, Sc) in the samples of rare earth nodular graphite cast iron with satisfactory results.The second chapter presents a new procedure for determination of trace cerium based on the adsorption voltammetry of the Ce3+- A1C complex at a CPE. The procedure is convenient to determine alone cerium in the presence of other rare earths because there is a 100 mV difference between the peak potentials of Ce3+- A1C and other rare earth(III)-ALC complexes in a supporting electrolyte of 0.08 mol/L HAc-NaAc and 0.012 mol/L potassium biphthalate(pH 4.7) when linear-scanning at 100 mV/s from -0.2 V to 0.8 V. The second-order derivative peak currents are directly proportional to Ce3+ concentration over a range of 6.0×10-9-3.0×10-7mol/L. The detection limit is as low as 3.0×10-9mol/L (S/N=3) for 120 s preconcentration times. The RSD of 3.5% is obtained for 15 determinations of Ce3+at 4.0×10-8mol/L level on a same CPE surface. The proposed method has been applied to determination of cerium in the samples of rare earth nodular graphite cast iron.The final chapter is devoted to electrochemical behavior of the scandium(III)-ALC complex at a CPE. A sensitive adsorptive oxidation peak of the scandium(III)-ALC complex is obtained at the peak potential of 0.66 V in 0.08 mol/L HAc-NaAc- 0.02 mol/L potassium biphthalate(pH4.3) when linear-scanning from -0.2 V to 0.8 V at 150 mV/s. The concentrations of Sc(III) are directly proportional to the second-order derivative peak currents over a range of 2.0×10-9-6.0×10-7 mol/L. The detection limit for scandium is as low as 1.0×10-9 mol/L (S/N=3) for 120 s accumulation time. The relative standard deviation is 3.7% for 15successive determinations on the same electrode surface at the 4.0×10-8 mol/L level. The electrode processes of the adsorbed complex are proposed. The method has been applied successfully to the determination of scandium in ore samples.From the above, adsorptive oxidation behavior of various rare earths (III)-ALC at a CPE is very different within the positive potentials. The difference can be used for determination of middle and heavy rare earths, cerium and scandium, respect更多还原