Mercury analysis in environmental samples by EDXRF and CV-AAS

The analysis of total Hg in various environmental matrices was investigated using energy dispersive X-ray fluorescence (EDXRF) for both powdered and digested samples and cold vapor atomic absorption (CV-AAS) for digested samples. Several microwave decomposition procedures were evaluated with respect to the determination of Hg by CV-AAS and EDXRF. The use of different acid mixtures, microwave power settings and decomposition times were compared as well as the analysis on wet and freeze-dried samples. A set of standard reference samples were used to evaluate the procedures: NBS Citrus leaves (1572), NRC Pine needles (1575), NRC Dogfish muscle tissue (DORM-2), NRC Dogfish liver tissue (DOLM-2), BCR Human hair (397), BCR Coking coal (181) and NRC Marine sediment (PACS-1). An H(2)SO(4)/HNO(3)/H(2)O(2) acid mixture was found to be optimal for the complete mineralization and digestion of biological samples for I-Ig by CV-AAS whereas for EDXRF both the HNO(3)/H(2)O(2) and H(2)SO(4)HNO(3)/H(2)O, acid mixture gave good results. The detection limit of EDXRF could significantly be decreased (from 0.2 mu g/g to 0.058 mu g/g) by performing the analysis with digested samples. A good agreement was obtained between CV-AAS and EDXRF analysis. The obtained results were also in good agreement with certified values. The methods were applied to environmental samples (coal, trees, leaves, spinach, fish, sediments) and human hair in a coal mining area and in places where they use coal for cooking in Vietnam.