Sequential injection standard addition for on-line measurement of mercury in the river Elbe

Abstract

The improvement of reliability by a sequential injection procedure for on-line standard addition is described. This procedure is applied to a monitor for on-line determination of mercury in river water at concentrations from 20 to 1000 ng/l. The flow injection cold vapour atomic absorption spectrometry measurement include an on-line digestion by BrCl and UV-irradiation. The instrumental arrangement is controlled by the home-made software “FIMS-Master” (programmed based on LabView ®). During standard addition period, a selector valve is switched that alternately for 1 s standard (500 and 1000 ng/l, respectively) and for 9 s sample is transported to the injection valve. Standard and sample are mixed on the way to the injection valve by dispersion. The instrument has been tested at the German monitoring stations of Schnackenburg and Schmilka at 474.5 and 4.0 km from Czech border, respectively. Details are published at the web: http//www.rzbd.fh-hamburg.de/∼prmercol.