Studies On The Adsorption Voltammetry Of The Complexes Of Zirconium (Ⅳ), Vanadium (Ⅴ) At Carbon Paste Electrodes

The complexes of zirconium and vanadium were investigated byadsorptive voltammetry at a carbon paste electrode (CPE). The newapproaches were provided for determination of vanadium andnon-electroactive metal such as zirconium. The paper consists of four chapters. In the first chapter the adsorptive voltammetry for thedetermination of zirconium is dealed with in the presence oferiochrome blue black R (EBBR) at a CPE. The zirconium(Ⅳ)–EBBR complex can be adsorbed on the surface of theCPE, and produces a peak at –0.29 V (vs. SCE) whenlinear-scanning from 0.4 V to –0.6 V. Optimal analyticalconditions were found to be: 0.14 mol/L HCl, at 0.4Vaccumulation potential for 80 S and at 300 mV/s scan rate. Thelinear range is 9.0×10-9～ 9.0×10-8 mol/L (4.0×10-7 mol/LEBBR) and 9.0×10-8～1.0×10-6 mol/L (5.0×10-6 mol/L EBBR).The detection limit for zirconium (Ⅳ) is as low as 5.0×10-9mol/L (S/N=3) when the accumulation time is 150 seconds.The proposed method has been applied successfully to thedetermination of zirconium in standard samples. Hafniumproduces also an adsorptive wave at –0.29 V under the sameexperiment conditions, but the sensitivity is much lower thanthat of zirconium. It shows that the system could determinateselectively zirconium in the presence of trace amount ofhafnium. In the second chapter a new procedure for determination ofzirconium is presented based on anodic adsorptive stripping of thezirconium (Ⅳ)–Pyrocatechol Violet (PV) complex at a CPE. Thezirconium (Ⅳ)–PV complex can be adsorbed on the surface of theCPE, and produces a peak at 0.85 V (vs. SCE) when linear-scanningfrom 0.4 V to 1.4 V. Optimal analytical conditions were found to be:0.08 mol/L HCl, at 0.4V accumulation potential for 50 s and at 100mV/s scan rate. The linear range is 3.0×10-9～5.0×10-8 mol/L (5.6×10-7 mol/L PV) and 1.0×10-8～1.0×10-7 mol/L (5.6×10-6 mol/L PV).The detection limit is 1.0×10-9 mol/L (S/N=3) for accumulation 50 s.The proposed method has been applied successfully to thedetermination of zirconium in standard samples of ore withoutextracting and sheltering, with satisfactory results. In the third chapter a new procedure for determination of tracevanadium is presented based on the adsorption voltammetry of thevanadium (V)–EBBR complex at a CPE. The vanadium (V)–EBBRcomplex can be adsorbed on the surface of the CPE and produces aanodic peaks at 1.17 V (vs. SCE), when linear-scanning from 0.4 V to1.4 V. Optimal analytical conditions were found to be: 0.2 mol/LHAc-NaAc (pH4.7), at 0.4 V accummulation for 420s or 120 s and at300 mV/s scan rate. The linear range is 9.0×10-10～6.0×10-8 mol/L(1.2×10-6 mol/L EBBR) and 6.0×10-8～6.0×10-7 mol/L (3.0×10-6mol/L EBBR). The detection limit is as low as 4.0×10-10 mol/L(S/N=3) for accumulation 450 s. The proposed method has beenapplied successfully to the determination of vanadium in peanut andtap water. In the last chapter electrochemical behavior of thevanadium (V)–lumogallion (LMG) complex is devoted to at aCPE. The vanadium (V)–LMG complex can be adsorbed on thesurface of the CPE and produces a anodic peak at 0.81V (vs.SCE) when linear-scanning from 0.4V to 1.4V. Optimalanalytical conditions were found to be: 0.26 mol/L HAc-NH4Ac(pH4.3), for accumulation 120 s at 0.4V and at 300 mV/s scanrate. The linear range is 4.0×10-9～1.0×10-7 mol/L (5.0×10-7mol/L LMG) and 1.0×10-7～1.2×10-6 mol/L (2.0×10-6 mol/LLMG) The detection limit for vanadium(V) is as low as1.0×10-9 mol/L (S/N=3). The proposed method has beenapplied successfully to the determination of vanadium inflying coal-ash, fly-ash and tap water.