Determination of methyl mercury and inorganic mercury in natural waters at the pgL −1 level: Intercomparison between PT-GC-Pyr-AFS and GC-ICP-MS using Ethylation or Propylation derivatization
Résumé
Mercury speciation anal. of both inorg. and Me Hg in ultrapure and natural waters by purge-and-trap gas chromatog. pyrolysis at. florescence spectrometry (PT-GC-Pyr-AFS, MERX-M, Brooks Rand) was performed. This automated anal. setup was also compared with gas chromatog. inductively coupled plasma mass spectrometry (GC-ICPMS, X Serie 2 ThermoFisher). In addn., a reagent cleaning step of the buffer soln. and derivatizing reagents (NaBEt4 and NaBPr4) was evaluated to improve the detection limit of the method. PT-GC-Pyr-AFS expts. analyzing Milli-Q and Deionized water (Millipore) using cleaned reagents and quantifying by external calibration led to MeHg+ and Hg2+ concn. values significantly lower than those obtained using uncleaned reagents. The limit of detections (LODs) after cleaning was found significantly low using both NaBEt4 and NaBPr4. However, the lowest LODs were obtained when using cleaned NaBPr4 (range: 1-2 pgL-1 for MeHg+ and 9-10 pgL-1 for Hg2+). Matrix effects have been finally investigated using both PT-GC-Pyr-AFS and GC-ICPMS to characterize and quantify potential interferences in natural water samples with different salinities and org. matter contents, including coastal water ref. material (CRM) certified for total mercury concn. (IRMM BCR-579).
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