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

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 1000ng/l. The flow injection cold vapour atomic absorption spectrometry measurement include an on-line digestion by BrCl and UVirradiation. The instrumental arrangement is controlled by the home-made software "FIMSMaster" (programmed based on LabView®). During standard addition period, a selector valve is switched that alternately for 1s standard (500 and 1000ng/l, respectively) and for 9s sample is transported to the injection valve. Standard and sample are mixed on the way to the injection valve by dispersion.