Flow system device for the on-line determination of total mercury in seawater

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 vapour atomic absorption spectrometry (CVAAS) detection limit was improved by a gold amalgam preconcentration 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 = 0.039c + 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. (C) 2000 Elsevier Science B.V. All rights reserved.