Application of adsorptive cathodic differential pulse stripping method for simultaneous determination of copper and molybdenum using pyrogallol red

A reliable and sensitive procedure for the simultaneous determination of trace levels of copper and molybdenum is proposed. The complexing of copper(II) and molybdenum(VI) with pyrogallol red (PGR) is analyzed by cathodic stripping differential pulse voltammetry based on the adsorption collection of the complexes onto a hanging mercury drop electrode (HMDE). The effect of chemical and instrumental parameters on the sensitivity and selectivity were studied. Copper and molybdenum peaks potential were observed at about +0.13 and −0.22 V versus Ag/AgCl electrode, respectively. A standard addition method was utilized for the analysis of voltammogram data, under the optimum conditions and with accumulation time of 90 s. The measured peak current at about +0.14 and −0.22 V is proportional to the concentration of Cu(II) and Mo(VI) over the range of 2-70 and 0.8-80 ng ml⁻¹, respectively. The limit of detection are 0.3 and 0.1 ng ml⁻¹ for Cu(II) and Mo(VI), respectively. The capability of the method for the analysis of real samples was evaluated by determination of copper and molybdenum in river water, tap water and alloy. Atomic absorption spectrometry was applied as a reference method for determination of copper and molybdenum in water samples.