The cyclic renewable mercury film silver based electrode for determination of molybdenum(VI) traces using adsorptive stripping voltammetry

The new cyclic renewable mercury film silver based electrode (Hg(Ag)FE), applied for the determination of molybdenum(VI) traces using differential pulse adsorptive cathodic stripping voltammetry (DP AdSV) is presented. The Hg(Ag)FE electrode is characterized by very good surface reproducibility (≤2%) and long-term stability (more than 2 thousand measurement cycles). The preparation of the Hg(Ag)FE is very simple and its operation may be controlled automatically. The effects of various factors such as: preconcentration potential and time, pulse height, step potential and supporting electrolyte composition are optimized. The calibration graph is linear from 2 nM (192 ng L−1) to 200 nM (19 μg L−1) for an accumulation time of 15 s, with correlation coefficient of 0.9995. For a Hg(Ag)FE with a surface area of 3.5 mm2 the detection limit for an accumulation time of 60 s is as low as 8 ng L−1. The repeatability of the method at a concentration level of the analyte as low as 2.4 μg L−1, expressed as R.S.D. is 1.3% (n = 7). The proposed method was successfully applied and validated by studying the certified reference material TMRAIN-95 and simultaneous recovering of Mo(VI) from spiked water and sediment samples.