SELECTIVE DETERMINATION OF METHYLMERCURY BY FLOW-INJECTION FAST-SCAN VOLTAMMETRY

A simple flow-injection system, suitable for solution flow rates at mi croliters-per-minute, has been combined with fast-scan voltammetry for selective determination of methylmercury. A thin Hg film was formed a t a Pt microelectrode prior to the measurement. Detection of methylmer cury is carried out by measuring the oxidation of methylmercury radica ls that have been generated at the Hg microelectrode. At slow scan rat es, the electrogenerated methylmercury radicals undergo a follow-up di merization reaction to form dimethyldimercury (ErCi2 mechanism). At fa st scan rates, it was found that methylmercury radicals can be quantit atively 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 leve l of subnanomole was obtained with a sample consumption of less than 1 0 mu L and the concentration detection limit for methylmercury at 50 V /s was estimated to be about 0.56 mu M. To demonstrate the applicabili ty of this method to automatic analyses, repetitive fast-scan cyclic v oltammetry was conducted in conjunction with multiple sample injection s. Determination of methylmercury in the presence of excess inorganic mercury was also conducted. This new approach to methylmercury determi nation was successfully applied to the analysis of elevated dogfish mu scle samples.