Determination of total Hg isotopic composition at ultra-trace levels by on line cold vapor generation and dual gold-amalgamation coupled to MC-ICP-MS

摘要

An online pre-concentration method was developed to directly determine Hg isotopic compositions at the ng L~(-1) level in liquid samples. It is based on the hyphenation of a commercially available cold vapor generation dual gold amalgamation system to a multi-collector ICP-MS. This automated method supports a rapid throughput and consumes less than 100 mL of sample (20-90 mL), representing a decrease of the sample size of more than two orders of magnitude in comparison to existing off-tine pre-concentration strategies. The accuracy and the precision were evaluated by the analysis of a secondary standard (UM Almaden) and results for a Hg concentration of 5 ng L~(-1) were δ~(202)Hg = -0.55 ± 0.26‰ and ⊿~(199)Hg = -0.02 ± 0.15%o (±2SD, n = 14). The method has been compared to the actual reference technique with the analysis of 6 environmental reference materials. Direct on line cold vapor generation and dual gold-amalgamation coupled to MC-ICP-MS demonstrates its relevant applicability for low Hg concentrated environmental samples (undersized biological samples, natural waters).