A new fully automated on-line digestion system for ultra trace analysis of mercury in natural waters by means of FI-CV-AFS

A fully automated flow injection (FI) system utilizing the extraordinary oxidation power of bromine monochloride (BrCl) for the transformation of dissolved mercury species to Hg2+ and oxidation of dissolved organic carbon (DOC) has been developed and coupled to cold vapor (CV) atomic fluorescence spectrometry (AFS) for highly sensitive mercury detection. The system can be applied to natural waters, sea water as well as freshwater and provides a detection limit as low as 16 pg Hg l−1 from a sample volume of 7 ml. The relative standard deviation is about 4–10%. A 3-fold measurement of one sample is completely processed within 15 min. Dissolved organic carbon, chloride and iodide ions are tolerated in concentrations of 15 mg DOC l−1, >21 g Cl− l−1, and 10 mg I− l−1. Validation of the proposed method yielded a good recovery of total mercury in a moorland water sample and in the certified reference material ORMS-3, river water. Investigation of eight real water samples with mercury concentrations in the range of 0.3–1.4 ng l−1 also confirmed the suitability of the proposed method.