Methylmercury determination in seafood by photochemical vapor generation capacitively coupled plasma microtorch optical emission spectrometry

A non-chromatographic method based on double liquid-liquid extraction and measurements by UV photochemical vapor generation capacitively coupled plasma microtorch optical emission spectrometry was developed and characterized for methylmercury determination in seafood. Samples were prepared following the procedure recommended in JRC Technical Report of European Commission formerly proposed for the determination of methylmercury in seafood by thermal decomposition atomic absorption spectrometry, namely confinement of Hg species in 47% HBr solution, extraction of CH3Hg+ in toluene and back-extraction in 1% L-cysteine aqueous solution. Mercury cold vapor was generated by flow injection UV photo-reduction from CH3Hg+ in 0.6 mol L-1 HCOOH, while quantification was performed against external Hg2+ aqueous standards and measuring Hg 253.652 nm emission using a low power/Ar consumption plasma microtorch (15 W, 100 mL min(-1)) and a low resolution microspectrometer (Ocean Optics). The figures of merit and analytical capability were assessed by analyzing certified reference materials and test samples of fish fillet and discussed in relation with requirements for Hg determination in seafood in European legislation (Decisions 2007/333/EC and 2002/657/EC) as well as compared to performances achieved in thermal decomposition atomic absorption spectrometry. The limit of detection and quantification of 2 mu g kg(-1) and 6 mu g kg(-1) respectively, precision of 2.79.4% and accuracy of 99 +/- 8% of the proposed method for the determination of CH3Hg+ fulfill the demands of European legislation for Hg quantification. The limit of detection and quantification were better than those in the used reference method or other non-/chromatographic methods taken for comparison. The analysis of certified reference materials and the Bland and Altman test performed on 12 test samples confirmed trueness of the proposed method and its reliability for the determination of traces of CH3Hg+ with 95% confidence level. The proposed method fulfills several demands of the eco-scale concept, is sensitive, simple and safe related to sample preparation through elimination of classical, harmful reductants and attractive by using economical miniaturized instrumentation incorporating a low power and low Ar consumption plasma.