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 degrees C and a low atomization temperature of 900 degrees C could be achieved by using both a PdCl2-coated pyrolytic graphite tube and a chemical modifier consisting of a 5% (NH4)(2)S 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. (C) 2000 Elsevier Science B.V. All rights reserved.