The application of gas chromatography-time-of-flight mass spectrometry to the analysis of monomethyl mercury at sub-picogram levels

Abstract

The analysis of sub-picogram-range methyl mercury generally requires complicated hyphenated instrumentation combining chromatographic systems for the separation and identification of organic Hg components (by GC–MS or LC–MS) and inorganic mass spectrometric techniques for their quantification. To eliminate the complexities and possible biases associated with such complicated hyphenated systems, it is highly desirable to develop a simplified but reliable single-stage instrumental method for the analysis of methyl mercury in environmental samples. To this end, this paper presents an analytical technique based on thermal desorption (TD) – GC – time of flight (TOF) mass spectrometry (MS) for the quantitative analysis of mono-methyl mercury (MMHg) prepared in a liquid phase standard. This optimized system was calibrated using standards in the range of 18pg to 45ng and yielded a coefficient of correlation of R2=0.9996. This GC-TOF-MS system allowed very low detection limits for MMHg (MDL=1.86pg and LOD=0.031pg) with good reproducibility (RSE=1.82%). The potential applicability of the GC-TOF-MS system is highlighted for the trace-level analysis of sub-pg-range of methyl mercury.