A new electrochemical method for the determination of trace molybdenum(VI) using carbon paste electrode modified with sodium dodecyl sulfate

A sensitive procedure was developed for the determination of trace molybdenum(VI) by adsorptive anodic stripping voltammetry based on the oxidation of molybdenum(VI)–2′,3,4′,5,7-pentahydroxyflavone (morin) complex at a sodium dodecyl sulfate modified carbon paste electrode (denoted as SDS/CPE). Compared with the poor response at a conventional paste electrode, the electrooxidation of molybdenum(VI)–morin complex at the SDS/CPE was greatly improved, as confirmed from the significant enhancement of peak current and the negative shift of peak potentials. The optimum conditions for the analysis of molybdenum(VI) include 0.1 M sulfuric acid, 3.0 × 10−5 M or 3.0 × 10−6 M morin, an accumulation potential of −0.1 V (versus SCE), an accumulation period of 60 s or 120 s and a scan rate of 0.1 V s−1. Under the selected conditions, the linearity between peak currents and concentrations of molybdenum(VI) existed for a wide range of 8.0 × 10−10–6.0 × 10−8 M (cmorin = 3 × 10−6 M) for 120 s accumulation and 6.0 × 10−8–6.0 × 10−6 M (cmorin = 3 × 10−5 M) for 60 s accumulation, a low detection limit (three times signal to noise) of 4.0 × 10−10 M was obtained after a 120 s preconcentration. The proposed method was successfully applied to the determination of molybdenum(VI) in real samples with enhanced selectivity.