Selective Determination of Methylmercury by Flow-Injection Fast-Scan Voltammetry

Authors

Rebecca Lai, University of Nebraska - LincolnFollow
Eva Huang, California State University, Los Angeles, Los Angeles, CA
Feimeng Zhou, California State University, Los Angeles, Los Angeles, CA
David O. Wipf, Mississippi State University, Mississippi State, MS

Date of this Version

July 1998

Comments

Published in Electroanalysis 10:13 (1998), pp.926–930. Copyright © 1998 WILEY-VCH Verlag GmbH, D-69469 Weinheim. Used by permission.

Abstract

A simple flow-injection system, suitable for solution flow rates at microliters-per-minute, has been combined with fast-scan voltammetry for selective determination of methylmercury. A thin Hg film was formed at a Pt microelectrode prior to the measurement. Detection of methylmercury is carried out by measuring the oxidation of methylmercury radicals that have been generated at the Hg microelectrode. At slow scan rates, the electrogenerated methylmercury radicals undergo a follow-up dimerization reaction to form dimethyldimercury (E_rC_i² mechanism). At fast scan rates, it was found that methylmercury radicals can be quantitatively reoxidized (reversible electron-transfer). Optimization of the experimental conditions of the system was performed based on studies of the relationship between the scan rate and the dimerization rate of the methylmercury radical. Under optimized conditions, detection level of subnanomole was obtained with a sample consumption of less than 10 μL and the concentration detection limit for methylmercury at 50 V/s was estimated to be about 0.56 μM. To demonstrate the applicability of this method to automatic analyses, repetitive fast-scan cyclic voltammetry was conducted in conjunction with multiple sample injections. Determination of methylmercury in the presence of excess inorganic mercury was also conducted. This new approach to methylmercury determination was successfully applied to the analysis of elevated dogfish muscle samples.