On-line determination of total mercury in the Baltic Sea

A novel and expeditious approach for the direct determination of total mercury in seawater coupled on-line to a flow manifold and a cold vapor atomic absorption spectrometer is described. The detection limit of 0.1ng/l was improved by optimizing the flow system, adding a drying unit for the mercury vapor and a gold amalgam preconcentration. The relative standard deviation of three measurements of 0.5ng/l Hg2+ was 2.7%. The long-time (12h) reproducibility was 6.2% R.S.D. (n=25) of 0.5ng/l Hg2+. The system has on-line UV digestion with a recovery rate of about 90% and a throughput of 10samples/h. The accuracy of the method was evaluated by the analysis of certified reference materials. The results showed good agreement with the certified values. The system was applied on the research vessel Alexander von Humboldt (Baltic Sea Research Institute, Warnem?nde, Germany) in the Baltic Sea. Total mercury concentrations [HgT] were measured in the surface water in a range of 0.2-1.87ng/l. The technique is fast, simple to handle and robust.