Determination of mercury in environmental samplesby gold-coated graphite furnace atomic absorption spectrophotometry with cold vapor generation

Abstract

Mercury is determined at the sub-parts per trillion level by a combination of cold vapor generation, gold-coated graphite furnace trapping and atomic absorption detection. The mercury is reduced by stannous chloride to elemental cold vapor, stripped from solution by nitrogen gas stream and collected onto a gold-coated porous graphite disk in a graphite furnace. It is then atomized by increasing the graphite furnace temperature and detected by an atomic absorption spectrophotometer. The absolute detection limit and the sensitivity were found to be 5 pg and 20 pg/0.0044 absorbance of mercury, respectively. The concentration limit of detection was 0.1 ng/1 for a 50-ml sample with three orders of magnitude of the linear dynamic range. The precisions of the measurements were 2.7 \% for 0.1 ng and 2.6 \% for 2 ng of mercury. Analyses of NBS and NIES reference materials showed quantitative recovery. Analytical results obtained by the present technique are presented for natural waters, marine biota, settling particulates, marine sediments and ambient air.