Validation and application of an analytical method for monomethylmercury quantification in aquatic plant tissues

An analytical methodology for monomethylmercury (MMHg) determination in aquatic plant tissues with low detection limit (346 pg g(-1)) is proposed. It consists of acid digestion (HBr/CuSO4), cleanup step with a Na2S solution, pre-concentration procedure using a dithizone solution in toluene and quantification by GC-ECD. The performance of the methodology has been tested by determining the MMHg concentrations in the certified reference material Fucus Sea Plant Homogenate--IAEA-140/TM (CRM) and in leaves, stems and roots of the salt marsh plants Sarcocornia fruticosa and Halimione portulacoides. The results obtained for CRM were not statistically different (alpha=0.056) from the certified value and repeatability was lower than 2.5% for the plant samples analyzed. This coefficient of variation was similar to those obtained in the externally quality control using within-batch and between-batch (<1.4%).