Adsorptive Voltammetric Technique Research Articles

Sensitive adsorptive stripping voltammetric method for direct determination of trace concentration of lead in the presence of cupferron in natural water samples

This paper reports the use of an adsorptive voltammetric technique for Pb(II) determination using cupferron as a selective complexing agent. After accumulation of the complex onto a hanging mercury drop electrode, the electrode potential was scanned with differential pulse modulation and the reduction current of lead was observed at about −0.5 V. Under optimum conditions (5 × 10−4 mol L−1 cupferron concentration, 0.1 mol L−1 acetate buffer (pH 5.5), adsorption at −50 mV for 30 s) the detection limit was 5.1 × 10−10 mol L−1. The relative standard deviation of five measurements for low lead concentration was 3.1%. The accuracy of the method was tested by analysing certified reference material (SPS-WW1 Waste Water). Finally, the method was successfully applied to the determination of Pb(II) in river water samples without any pretreatments.

Simultaneous determination of trace amounts of cadmium, nickel and cobalt in water samples by adsorptive voltammetry using ammonium 2-amino-cyclopentene dithiocarboxylate as a chelating agent

This paper reports the use of an adsorptive voltammetric technique for the simultaneous detection of Cd(II), Ni(II) and Co(II) using ammonium 2-amino-cyclopente dithiocarboxylate as a selective complexing agent. Scans containing three resolved peaks corresponding to these metals were obtained in synthetic and real samples. The reduction current peaks of the metals that were distinctly separated by 200 mV or more, allowing their determination over a wide range of concentrations. These metals can be quantified at concentrations above 1.33×10 −8 mol dm −3 Cd(II), 8.51×10 −9 mol dm −3 Ni(II) and 3.39×10 −10 mol dm −3 Co(II). The influence of pH, ligand concentration, scan rate, accumulations time and applied potential was investigated. The R.S.D. at a concentration level of 1.78×10 −7 mol dm −3 of Cd(II), 3.40×10 −7 mol dm −3 and Ni(II) and 1.7×10 −9 mol dm −3 of Co(II) was 2.5% for Cd(II), 2.7% for Ni(II) and 3.3% for Co(II). The method was applied to various water samples.

Adsorptive cathodic stripping voltammetric determination of ultra-trace concentrations of vanadium on a glassy carbon mercury film electrode

The determination of trace and ultra-trace concentrations of vanadium(V) by adsorptive cathodic stripping voltammetry on a glassy carbon mercury film electrode is described. The method involves a controlled preconcentration of the element by interfacial accumulation as vanadium-pyrogallol complex on the electrode followed by cathodic stripping voltammetric measurement. The optimum analytical conditions for the measurement of vanadium by this method include the use of 0.20 M acetate buffer at pH 5.6 to 5.8, 5 × 10 −4 M pyrogallol, an accumulation potential of −0.30 V vs. Ag/AgCl and a rotated electrode at 1920 rpm. The study of inorganic interference indicated that metal ions generally do not interfere with the vanadium determination, except for Pb(II) ions. However, the effect of this interference is eliminated by the addition of EDTA into the solution. The interference of surface-active substances, e.g., Triton X-100, is overcome by UV irradiation of the sample. For a 3-min accumulation, the linear concentration range obtained is 0–75 μg l −1 ( R 2 = 0.948) and lowest detectable amount is 1.0 μg l −1 (R.S.D. = 9.5%). The use of the adsorptive voltammetric technique after dry-ashing and UV treatment of the samples is successfully demonstrated for the determination of vanadium in standard biological and environmental reference materials.

Adsorption voltammetric techniques for the determination of uranium(VI) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone as complex forming reagent

Uranium (VI) can be determined by adsorptive voltammetric techniques, as its chloranilic acid complex, over a wide concentration range. Differential pulse polarography is useful for quantification of uranium between 0.1 and 1.5 mg/l; for the range from 10 to 500 μg/l differential pulse voltammetry and for ultra-trace analysis between 0.024 and 40 μg/l adsorptive stripping voltammetry are preferred. The standard deviation for the 3σ-detection limit of 24 ng/l uranium was found to be 8%. In the trace analysis of metals in aquatic environmental systems by adsorptive stripping voltammetry it is normally necessary to decompose polluted water samples by UV irradiation or microwave digestion. The advantage of the developed method is the fact that no sample pretreatment is necessary.