Simultaneous determination of trace amounts of vanadium and molybdenum in water and foodstuff samples using adsorptive cathodic stripping voltammetry

Summary A new procedure is presented for the simultaneous determination of ultra trace amounts of vanadium and molybdenum based on adsorptive cathodic stripping voltammetry (AdCSV). Adsorptive accumulation of the V(V) and/or Mo(VI) with chromoxane cyanine R (CCR) onto a hanging mercury drop electrode, followed by reduction of the adsorbed species using differential pulse voltammetry method. Optimised conditions include a 60 s adsorption period at −0.10 V, 8.0  μ m of CCR in 0.1  m acetate buffer, pH 3.6, and a voltammetric scan using differential pulse mode with 25 mV s −1 scan rate. Detection limits of 0.1 and 0.08 ng mL −1 were achieved for V(V) and Mo(VI), respectively, which can be lowered down to 0.06 and 0.04 ng mL −1 by extending the adsorption time to 180 s. The reduction currents are linear in the range of 0.3–24.0 ng mL −1 and 0.1–30.0 ng mL −1 for V(V) and Mo(VI), respectively. The relative standard deviation for ten replicates determination of 4.0 ng mL −1 V(V) and Mo(VI) were 1.8% and 1.1%, respectively. The proposed method applied for the determination of vanadium and molybdenum in river water, tap water, well water and plant foodstuff such as cucumber, tomato, carrot and tea.