The determination of ultra-trace (ppt) mercury content by the CV AAS without preconcentration (Abstract)
Sholupov, S.1, Pogarev, S.2; Ryzhov, V.2 and Christensen, I.3
1”Lumex Ltd”, St. Petersburg, Russia; 2Earth Crust Research Institute, St. Petersburg State University, Russia;
3Danish Technological
The cold-vapor atomic absorption spectroscopy (CV AAS) is presently the most widely used technique for determination of mercury in environmental and biological samples. To attain the ppt detection limits of the CV AAS, the mercury preconcentration in the absorption traps is used. However, a change in the mercury collection efficiency caused by various processes (ageing, saturation, poisoning) gives rise to errors in measurements. Therefore, it is often necessary to bring in a standard sample to allow for the change in the collection efficiency. Moreover, if the trap is used, the flow rate of the carrier gas is rather low (about 1 l/min), which leads to “memory effects” and longer analysis time when mercury is released from the reaction vessel. This causes a decrease in the productivity and an increase in the cost of analyses.
We propose a different approach for lowering the detection limit: to use a multipass analytical cell, which significantly enhances the sensitivity of analyses. In our case, a change in the radiation transmission in the multipass cell is eliminated due to the use of the Zeeman atomic absorption spectrometry using high frequency modulation of light polarization (ZAAS-HFM). In this paper, we report our results on the determination of mercury in various samples, such as natural and waste water, industrial emissions, etc., which have been obtained using an RA-915+ analyzer with a built-in 40-cm-long multipass cell, its optical length being 960 cm, and with a single-pass cell, whose optical length is 6 cm, combined with a flow injection system (FIS). The use of a multipass cell makes it possible to lower the detection limit down to. 0,0002 mgL-1 and to increase the flow rate of the air pumping up to 4 l/min.