Clean conditions for the determination of ultra-low levels of mercury in ice and snow samples

Laboratory facilities and methods are presented for the determination of ul tra-low levels of mercury (Hg) in ice and snow samples originating from pol ar ice caps or temperate regions. Special emphasis will be given to the pre sentation of the clean laboratory and the cleaning procedures. The laborato ry is pressurized with air filtered through high efficiency particle filter s. This first filtration is not enough to get rid of contamination by Hg in air. Experiments are conducted in a clean bench, especially built for Hg a nalysis, equipped with both particle filter and activated charcoal filter. It allows to obtain very low levels of atmospheric Hg contamination. Ultrap ure water is produced for cleaning all the plastic containers that will be used fur ice and snow samples and also for the dilution of the standards. H g content in laboratory water is about 0.08 +/- 0.02 pg/g. A Teflon system has been developed for the determination of Hg in ice and snow samples base d on Hg(II) reduction to Hg(0) with a SnCl2/HNO3 solution followed by the m easurement of gaseous Hg(0) with a Hg analyzer GARDIS 1A+ based on the Cold Vapor Atomic Absorption Spectroscopy method. Blank determination is discus sed.