Determination of mercury in filtered sea-water by flow injection with on-line oxidation and atomic fluorescence spectrometric detection

A flow injection (FI) atomic fluorescence method incorporating an on-line bromide–bromate oxidation step to determine mercury in filtered sea-water samples at the ng l–1 level is described. A heated reaction coil was incorporated in the FI manifold to increase the conversion of organic mercury into inorganic mercury(II) chloride from 50 to approaching 100%. Detection limits (3σ) for mercury(II) chloride and methylmercury chloride were 25 and 23 ng l–1 Hg, respectively. The FI manifold could also be used to determine the total mercury concentration in biological materials and was validated by analysing the CRM TORT-1 Lobster Hepatopancreas. Good agreement with the certified (330 ± 60 µg l–1) value was achieved (353 ± 64 µg l–1). The analysis of coastal water samples from Sutton Harbour, Plymouth, showed that mercury levels ranged from 24 ± 5 to 54 ± 10 ng l–1.