A simple classical wet digestion technique for the determination of total mercury in fish tissue by cold-vapour atomic absorption spectrometry in a low technology environment

Four classical wet digestion procedures for the determination of mercury (Hg) by cold-vapour atomic absorption spectrometry in fish tissue were investigated with the aim of selecting and optimising the most convenient and inexpensive for use in a low technology environment. A mixture of H2O, HNO3, HClO4 and H2SO4 or a mixture of HCl, HNO3, HClO4 and H2SO4 was used for the digestion in two different vessels namely thick walled long neck 50 ml volumetric flask and 50 ml 26 mm × 200 mm pyrex test tube. The effect of temperature and time on the digestion efficiency of the mixture of HCl, HNO3, HClO4 and H2SO4 using test tubes were investigated to obtain the optimum conditions. Mercury was partly lost at temperatures above 230 °C and this was pronounced when decomposition time was more than 30 min. Detection limit for the optimised procedure was 0.52 ng g−1. The optimised procedure was employed to study the level of Hg in canned fish samples. Concentration of Hg in the samples tested ranged from 0.015 to 0.139 μg g−1 wet weight.