A rapid and simple microwave-assisted digestion method with alkaline solution (tetramethylammonium hydroxide or methanolic KOH solution) for speciation analysis of inorganic mercury and methylmercury (MeHg ⁺ ) in biological tissues was developed. Extracts with quantitative recoveries of mercury species after microwave-assisted alkaline dissolution of the sample were directly analysed by an automated on-line hyphenated system incorporating aqueous hydride generation, cryogenic trapping, gas chromatography and detection by atomic absorption spectrometry. Optimum conditions allow sample throughput to be controlled by the instrumental analysis time (≈10 min per sample) and not by the sample preparation step. At a power of 40–60 W, sample preparation time is only 2–4 min, which is much faster than previous literature methods. The proposed method was validated by the analysis of three biological certified reference materials, CRM 463, DORM-1 and TORT-1, and one BCR sample from an interlaboratory study, Tuna Fish 2. The detection limit of the overall procedure was found to be 3 ng per gram of pulverised dried biological tissue, for both labile Hg ²⁺ and MeHg ⁺ . After alkaline extraction, a mean recovery of 102% with a relative standard deviation of 7% was obtained for methylmercury concentrations ranging from 0.128 to 3.464 µg g ^-1 as Hg in the four reference fish tissues mentioned above. Total mercury, calculated as the sum of determined inorganic mercury and methylmercury, was also in agreement with the certified values. The methylmercury extraction efficiency of five extractants, viz. , nitric, hydrochloric and acetic acid, and tetramethylammonium hydroxide and methanolic KOH solution, the temperature profile of these extractants under microwave irradiation and the behaviour and stability of methylmercury in a focused microwave field were also investigated.

A fully automated on-line hyphenated system for mercury speciation analysis in environmental samples is presented. It provides derivatization by hydride generation or ethylation, preconcentration by cryotrapping, separation by packed column gas chromatography and detection by quartz furnace atomic absorption spectrometry. Automation of the hyphenation results in improved reproducibility of the analysis. The system has been specifically optimised for analysis of mercury compounds, but it is also potentially operative for other hydride- or ethylated derivative-forming elements, after the corresponding optimisation. Main advantages and potential limitations of the system are discussed. General procedures for the analysis of both solid (sediments, biotissues, suspended particulate matter) and liquid (sea and fresh water) samples are proposed and validated by analysis of certified reference materials. The obtained methylmercury and inorganic mercury concentrations are in agreement with the certified values. Detection limits of the method have been estimated as 0.5 ng g^–1 , 3 ng g^–1 , 0.1 ng l^–1 for both mercury species in dry sediments, biological tissues and aqueous samples, respectively. Analysis of one sample only requires 10 min (hydride generation) or 20 min (ethylation), so that a sample throughout of 6 or 3 samples h^–1, respectively, may be achieved. Results from the analysis of real samples collected in the Gironde and Scheldt estuaries (sediments, suspended particulate matter, water and biological tissues) are also provided.