Adsorptive stripping voltammetric determination of ultratrace concentrations of molybdenum in biological and environmental materials on a glassy carbon mercury film electrode

Abstract

Abstract The determination of ultratrace concentrations of molybdenum( VI ) 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 molybdenum‐8‐hydroxyquinoline (oxine) complex on the electrode followed by a cathodic stripping voltammetric measurement. The optimum analytical conditions for the measurement of molybdenum by this method include the use of 0.20 M acetate buffer at pH 5.25, 1 mM oxine, an accumulation potential of −0.40V (vs. Ag/AgCl) and a rotated electrode at 3000 rpm. Under these conditions, the linear concentration range and lowest detectable concentration obtained with a 5‐min accumulation were 0–300 μg L −1 ( R 2 = 0.997) and 0.5 μg L −1 [relative standard deviation (RSD) = 13.7%], respectively. The presence of most other metal ions do not interfere with the molybdenum determination, except for Pb II and Cd II which were successfully masked by addition of 3 μM EDTA, and Ti IV and W VI which were masked by 1 μM tartaric acid. The interference of surface‐active substances, such as Triton X‐100, is overcome by UV irradiation of the sample. The use of the adsorptive stripping voltammetric technique, after decomposition by dry ashing and UV treatment, is successfully demonstrated for the determination of molybdenum in biological and environmental materials.

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Identifiers

DOI

10.1002/elan.1140070512

Journal

Electroanalysis

Year

1995