Supporting Electrolyte Manipulation for Simple Improvement of the Sensitivity of Trace Vanadium(V) Determination at a Lead-Coated Glassy Carbon Electrode

Abstract

The paper presents a very simple way to extremely improve the sensitivity of trace V(V) determination. The application of a new supporting electrolyte composition (CH₃COONH₄, CH₃COOH, and NH₄Cl) instead of the commonly used acetate buffer (CH₃COONa and CH₃COOH) significantly enhanced the adsorptive stripping voltammetric signal of vanadium(V) at the lead-coated glassy carbon electrode (GCE/PbF). A higher enhancement was attained in the presence of cupferron as a complexing agent (approximately 10 times V(V) signal amplification) than in the case of chloranilic acid and bromate ions (approximately 0.5 times V(V) signal amplification). Therefore, the adsorptive stripping voltammetric system with the accumulation of V(V)-cupferron complexes at -1.1 V for 15 s in the buffer solution (CH₃COONH₄, CH₃COOH, and NH₄Cl) of pH = 5.6 ± 0.1 was selected for the development of a simple and extremely sensitive V(V) analysis procedure. Under optimized conditions, the sensitivity of the procedure was 6.30 µA/nmol L^-1. The cathodic peak current of V(V) was directly proportional to its concentration in the ranges of 1.0 × 10^-11 to 2.0 × 10^-10 mol L^-1 and 2.0 × 10^-10 to 1.0 × 10^-8 mol L^-1. Among the electrochemical procedures, the lowest detection limit (2.8 × 10^-12 mol L^-1) of V(V) was obtained for the shortest accumulation time (15 s). The high accuracy of the procedure was confirmed on the basis of the analysis of certified reference material (estuarine water) and river water samples.

Keywords: adsorptive stripping voltammetry; lead-coated glassy carbon electrode; sensitivity improvement; supporting electrolyte manipulation; vanadium.