Methylmercury and inorganic mercury determination in fish by cold vapour generation atomic absorption spectrometry

Given that organic mercury is more dangerous than the inorganic form and th at it is converted into methylmercury by biological methylation, we have st udied and optimized a simple method for measuring both organic and inorgani c mercury contents in fish, using a spectroscopic vapour generation techniq ue, with a sequential reduction of the digested sample with stannous chlori de and sodium tetrahydroborate. Prior to applying the method the sample was subjected to alkaline wet digestion. Due to the matrix interferences calib ration curves with matrix addition were needed for mercury determinations. The analytical parameters of the method were: linearity from 10 to 200 ng o f Hg in the reduction vessel; detection limit: 125 and 183 ng/g fresh sampl e for inorganic mercury and methylmercury, respectively; precision (RSD%): 9.8 and 10.1 for inorganic mercury and methylmercury, respectively; accurac y: reference material (Dorm-2-NRC-CNRC) for methylmercury; value found 4504 +/-272 ng/g; certified value 4470+/-320 ng/g. The method offers the advanta ge of not requiring special equipment to measure inorganic and organic merc ury simultaneously in a sample. To evaluate its usefulness it was applied t o nine different types of fish and mussels. (C) 2000 Elsevier Science;Ltd. All rights reserved.