Speciation of mercury in water and freshwater fish samples by a two-step solidified floating organic drop microextraction with electrothermal atomic absorption spectrometry.

A new and simple two-step SFODME using 4-nitro-o-phenylenediamine (4-NOPD) as a chelating agent was developed for mercury speciation in water and fish samples by ETAAS. For the first step, methylmercury was extracted into 1-undecanol and for the second step, the Hg(II) remaining in the sample solution was complexed with 4-NOPD and then extracted into 1-undecanol. Under the optimized conditions, the calibration graphs of Hg(II) and methylmercury were linear in the range of 0.83-8.0 µg L-1 and 0.78-8.0 µg L-1, with the LOD of 0.25 µg L-1 and 0.24 µg L-1 and the enrichment factor were 25.7 and 32.2, respectively. The %RSDs was in the range of 2.0-4.4% at concentrations of 0.5 and 4.0 µg L-1 (n = 5). The proposed method was successfully applied to mercury speciation in water and fish samples. The accuracy of method, tested by the analysis of SRM 1566b and DORM-4 was in good agreement with the certified values.