Direct determination of mercury in atmospheric particulate matter by graphite plate filtration–electrothermal atomic absorption spectrometry with Zeeman background correction

A new analytical method has been developed for direct analysis of mercury in atmospheric particulate matter by a graphite plate collection technique coupled with Zeeman electrothermal atomic absorption spectrometry (ETAAS). A small porous graphite plate filter was used initially for collecting particulates and subsequently as a platform in ETAAS. A relatively high ashing temperature of 250°C and a low atomization temperature of 900°C could be achieved by using both a PdCl2-coated pyrolytic graphite tube and a chemical modifier consisting of a 5% (NH4)2S solution. Excellent linearity was maintained over the range of 0–5 ng of Hg. When sampling at a flow rate of 350 ml min−1 for 3 h, this was equivalent to a working concentration range of 0–80 ng m−3 of particle-bound mercury in air. Analysis of the NIST SRM 1648, Urban Particulate Matter, gave a recovery of 101.4%, and a precision of 9.0% R.S.D. The detection limit was estimated to be 0.74 ng m−3. The accuracy was within ±8% when compared with the traditional glass-fiber filtration–acid digestion–cold-vapor atomic absorption spectrometry method.