Determination of inorganic and total mercury in biological samples treated with tetramethylammonium hydroxide by cold vapor atomic absorption spectrometry using different temperatures in the quartz cell

A very simple procedure is proposed for the determination of total and inorganic Hg in biological materials. Organic Hg ( methylmercury) can be obtained from the difference. After treating the sample at room temperature with tetramethylammonium hydroxide ( TMAH), inorganic Hg is obtained by cold vapor atomic absorption spectrometry (CV-AAS), keeping the quartz cell at room temperature, while total Hg is obtained by the same technique, heating the quartz cell in an air-acetylene flame. By analyzing several biological certified materials, it was evident that the difference between the mentioned concentrations corresponds to methylmercury. Cold vapor graphite furnace atomic absorption spectrometry (CV-GF-AAS) with retention of the vapor in a heated Au-treated graphite tube was used to optimize the vapor generation conditions and also to determine total Hg. In a general way, the concentrations obtained by both techniques were in agreement with the certified values or with differences of the certified values for total, Hg2+ and CH3Hg+, according to the t-test for a 95% confidence level. Total Hg results obtained by the two techniques were also in agreement. The relative standard deviations were lower than 10% for most of the results. The detection limits in the sample were: 0.13 mu g g(-1) for total Hg and 0.025 mu g g(-1) for Hg2+ by CV-AAS. The detection limit for total Hg by CV-GF-AAS was 0.001 mu g g(-1). It is amazing how this very simple method is able to provide very important information on mercury speciation.