Highly efficient electrocatalytic vapor generation of methylmercury based on the gold particles deposited glassy carbon electrode: A typical application for sensitive mercury speciation analysis in fish samples.

A gold particle deposited glassy carbon electrode (Au/GCE) was first used in electrochemical vapor generation (ECVG) technology and demonstrated to have excellent catalytic property for the electrochemical conversion process of aqueous mercury, especially for methylmercury (CH3Hg+), to gaseous mercury. Systematical research has shown that the highly consistent or distinct difference between the atomic fluorescence spectroscopy signals of CH3Hg+ and Hg2+ can be achieved by controlling the electrolytic parameters of ECVG. Hereby, a new green and accurate method for mercury speciation analysis based on the distinguishing electrochemical reaction behavior of Hg2+ and CH3Hg+ on the modified electrode was firstly established. Furthermore, electrochemical impedance spectra and the square wave voltammetry displayed that the ECVG reaction of CH3Hg+ may belong to the electrocatalytic mechanism. Under the selected conditions, the limits of detection of Hg2+ and CH3Hg+ are 5.3 ng L-1 and 4.4 ng L-1 for liquid samples and 0.53 pg mg-1 and 0.44 pg mg-1 for solid samples, respectively. The precision of the 5 measurements is less than 6% within the concentration of Hg2+ and CH3Hg+ ranging from 0.2 to 15.0 μg L-1. The accuracy and practicability of the proposed method was verified by analyzing the mercury content in the certified reference material and several fish as well as water samples.