Abstract: The instrumental set-up for the on-line sampling, digestion and quantification of total mercury in seawater is described. Based on a flow system and cold vapor atomic absorption spectrometry (CVAAS) detection limit was improved by a gold amalgam pre-concentration to 0.5 ng L-1. The manifold design was optimized by the variation of the gas flow, length of reaction coils, shape and material of the gas-liquid separator and flow rate of the reductant. A calibration following the equations p = 0.039 c + 0.0813 (p, peak area; c, concentration) and a correlation coefficient of r = 0.9996 was obtained. The relative standard deviation of three measurements of 0.5 ng L-1 Hg2+ was 3.8%. The long-time (12 h) reproducibility was 6.2% RSD (n = 25) of 0.5 ng L-1 Hg2+. With a recovery rate >90% mercury can be determined after on-line UV digestion. For a complete analysis, 6 min is required. The technique is fast, simple to handle and robust. The apparatus is designed for the use on research vessels under sea conditions.

Abstract: The development of an apparatus for the online sampling, digestion and quantification of total mercury in surface water is described. Detection and quantification is done by flow injection cold vapor atomic absorption spectroscopy (FI-CVAAS). Three digestion methods were tested, chemical, microwave and UV, The influence of the digestion parameters (digestion method, digestion time, microwave power, concentration of oxidation solution) on the recovery of mercury in water of the river Elbe have been investigated. Mercury can be determined almost quantitatively (recovery rate > 85%) with some digestion procedures described. The best results were reached by UV digestion. The technique is fast, simple to handle and robust. Each complete analysis only take four minutes. The working range is 10 to 1000 ng/L, The measuring arrangement has been applied successfully in a governmental monitoring station at Schnackenburg/Elbe, Germany.

Abstract: 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 0.1 ng/l was improved by optimizing the flow system, adding a drying unit for the mercury vapor and a gold amalgam pre-concentration. The relative standard deviation of three measurements of 0.5 ng/l Hg2+ was 2.7%. The long-rime (12 h) reproducibility was 6.2% RSD (n = 25) of 0.5 ng/l Hg2+. The system has on-line UV digestion with a recovery rate of about 90% and a throughput of 10 samples/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, Warnemunde, Germany) in the Baltic Sea. Total mercury concentrations [Hg-T] were measured in the surface water in a range of 0.2-1.87 ng/l. The technique is fast, simple to handle and robust.