Determination of metallic mercury and some organomercury compounds using atomic absorption spectrometry after amalgamation on a gold column

Abstract

The thermal desorption behaviour of metallic mercury and some organomercury compounds (methylmercury chloride, dimethylmercury and diphenylmercury) from a gold column has been studied. However, none of the mercury compounds investigated could be quantitatively released from the gold column by a single desorption. This memory effect leads to an increase in the detection signal for consecutive injections. Obtaining a blank signal for the gold column between measurements was thus necessary, although for metallic mercury the blank signal was not measurable. The percentage of mercury released for the different mercury compounds depends on the heating temperature and the type of carrier gas used. Under optimum conditions, a ratio of the signal peak to the signal peak plus blank peak of 100% was found for metallic mercury and of 80% for methylmercury chloride. The release of organomercury compounds is controlled by the decomposition process as well as by diffusion in the gold metal at low temperatures, but from a given temperature onwards diffusion becomes the limiting factor. The occurrence of methylmercury chloride can also be checked qualitatively.