DETERMINATION OF MERCURY IN ENVIRONMENTAL-SAMPLES BY ISOTOPE DILUTION/ICPMS

The application of isotope dilution inductively coupled plasma mass spectrometry for the determination of mercury in sediment and water samples using an enriched Hg-201 spike is described. Sediment samples are determined directly after spiking with Hg-201 and a 1-h acid digestion. The procedural detection limit is 2 ng/g using a 0.5-g sample. Quantitative recovery is obtained on NRC reference standard (BEST-1), which is certified at 92 +/- 9 ng/g. Natural levels of mercury in water samples require preconcentration onto gold traps and subsequent electrothermal heating and purging of the traps with argon directly into the torch of the ICPMS. The procedural detection limit is 0.2 ng/L using a 200-mL sample. The accuracy of the method was evaluated using a river water standard (ORMS-1) from the National Research Council of Canada, certified at 6.8 +/- 1.3 ng/L. Results using this technique yield a value of 6.3 0.4 ng/L.