Rapid Wet Digestion Method for Determination of Total Mercury in Fish and Shells

Abstract

A rapid wet-ashing procedure for routine determination of total mercury in a wide variety of fish and shells of sample sizes as large as 5g is described.
The wet samples are fully digested with a mixture of sulfuric acid and perchloric acid for ten minutes on a hotplate of which surface temperature is kept at 250°C, after preliminary heating for five minutes. The end of digestion is certified with the addition of potassium permanganate solution. Then, the digested solution is transferred into a 100ml volumetric flask and diluted with distilled water. The total mercury is determined by flameless atomic absorption spectrophotometry.
The study has shown that the samples can be digested on a hotplate at a high temperature as 250°C without any potential loss of mercury. With respect to the rapidity of digestion, the use of perchloric acid as a decomposing agent prevails over that of vanadium pentoxide. The digestion procedure used by Deitz et al. depends on vanadium pentoxide as the decomposing agent.
The data presented have also shown quantitative recovery of mercury added to a variety of samples. The concentrations of mercury obtained by the method herein proposed are slightly higher than those by the official method adapted by the Ministry of Welfare in this country.