Carbon paste electrodes plated with a gold film for the voltammetric determination of mercury(<scp>II</scp>)

Abstract

Abstract Carbon pastes of different compositions were tested as supports for gold film electrodes. A paste containing highly‐viscous silicone oil as a binder was found the most suitable. Experimental conditions were optimized in order to develop a differential pulse anodic stripping voltammetric method for the determination of mercury in water samples. In a supporting electrolyte containing HNO 3 (0.1 mol/L), (KCl 0.02 mol/L) and tetrachloroaurate(III) for in situ plating with a gold film, the response of Hg was found to be linear in a concentration range from 1 × 10 −9 up to 2.5 × 10 −7 mol/L (0.2–50 μg/L; accumulation potential +0.2V (vs. Ag/AgCl); accumulation time 30 s–5 min) with a detection limit of about 2.5 × 10 −10 mol/L (50 ng/L) after accumulating for 30 min. Reliability of the method depended mainly on the concentration of Au III in the electrolyte which had to be chosen adequately, with respect to the concentration level of Hg II in the sample. Interferences from some ions with the determination of mercury were also studied. The method was tested on both model and real samples and the results agreed well with those obtained by reference determinations.