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

摘要

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 H_2O, HNO_3, HClO_4 and H_2SO_4 or a mixture of HCl, HNO_3, HClO_4 and H_2SO_4 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, HNO_3, HClO_4 and H_2SO_4 using test tubes were investigated to obtain the optimum conditions. Mercury was partly lost at temperatures above 230 ℃ 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.