Total Hg was measured in the digested samples by ICP-MS. Helium gas was used in the collision cell to avoid interference in the ICP-MS measurements. A solution of 9Be, 103Rh and 205Tl was used as the internal standard. The samples were quantified by means of an external calibration curve from inorganic mercury standards. Analyses in triplicate were performed for each sample. For quality control purposes, the standards of the calibration curve were run before and after each sample series. The corresponding digestion blanks (one for each sample digestion series) were also measured. Quality control standard solutions at two concentrations were measured at the end of the sequence to ensure stable instrument sensitivity. To assess the accuracy of the ICP-MS method, three CRMs (DOLT-4, TORT-2 and BCR-463) were
analysed