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 x 10(-5) M or 3.0 x 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 x 10(-10)-6.0 x 10(-8) M (c(morin) = 3 x 10(-6) M) for 120 s accumulation and 6.0 x 10(-8)-6.0 x 10(-6) M (c(morin) = 3 x 10(-5) M) for 60 s accumulation, a low detection limit (three times signal to noise) of 4.0 x 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. (C) 2011 Elsevier B.V. All rights reserved.