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

Abstract

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 μg g⁻¹ for total Hg and 0.025 μg g⁻¹ for Hg²⁺ by CV-AAS. The detection limit for total Hg by CV-GF-AAS was 0.001 μg g⁻¹. It is amazing how this very simple method is able to provide very important information on mercury speciation.