Application of Speciated Isotope Dilution Mass Spectrometry To Evaluate Extraction Methods for Determining Mercury Speciation in Soils and Sediments

Abstract

Extraction techniques commonly used to extract methylmercury or mercury species from various matrixes have been evaluated regarding their potential to transform inorganic mercury to methylmercury, or vice versa, during sample preparation steps by applying speciated isotope dilution mass spectrometry. Two of the five tested methods were highly prone to form inorganic mercury from methylmercury. Some published methods converted methylmercury to inorganic mercury approximately 100% (including the spiked CH(3)(201)Hg(+)). In other methods, as much as 45% of methylmercury was converted to inorganic mercury during extraction. The methods evaluated included cold acid extraction and sonication. Other methods, such as the proposed EPA RCRA Draft Method 3200, microwave-assisted extraction, and another sonication-based methods induced very little or no methylmercury transformation to inorganic mercury. Among these three methods, the proposed Draft EPA Method 3200 was found to be the most efficient.

High‐sensitivity capillary electrophoresis for speciation of organomercury in biological samples using hollow fiber‐based liquid‐liquid‐liquid microextraction combined with on‐line preconcentration by large‐volume sample stacking

“…The reason could be attributed to the decomposition caused by the presence of concentrated HNO 3 and 30% H 2 O 2 solution, which transforms organomercury species into inorganomercury species. Similar transformation of organomercury species was observed by Rahman and Kingston [33] in determination of mercury species by HPLC-ICP-MS. Therefore, the application of cold digestion for mercury speciation analysis would provide completely inaccurate information about the sample, and it is not suitable for accurate species measurement.…”

Robust microwave-assisted extraction protocol for determination of total mercury and methylmercury in fish tissues

“…Although this extraction technique offers significant benefits in terms of time, efficiency, solvent consumption and minimal risk of losing volatile compounds, only few applications have been described for mercury species in biological tissues [9,10,14]. Speciated isotope dilution mass spectrometry (SIDMS) [20,[24][25][26][27][28] a part of EPA Method 6800 [29] is a technique created specifically to account for these potential changes in native species distribution can greatly assist in the evaluation of analytical methods. SIDMS provides highly accurate and precise data as well as information regarding possible species transformations that occur during and/or after sample preparation.…”

Inter‐laboratory validation of EPA method 3200 for mercury speciation analysis using prepared soil reference materials

“…It was found from a previous study that EPA draft method 3200 had the highest extraction efficiency for both inorganic and organometallic fractions in comparison with other methods that do not induce transformations of the mercury species. 7 The design of the method, including mass balance options, permits the inorganic mercury recovery in multiple ways, for example in later stages as non-extractable mercury, which is mainly the less mobile and less toxic inorganic mercury species.…”

“…A description of each method studied, along with the final results, is reported elsewhere. 7 Heretofore, the technique for determining the speciation of mercury in soil and sediment samples was a succession of analytical steps: extraction, separation and detection. The results obtained have been 'operationally defined' using a given procedure.…”