On-line Isotope Dilution Determination of Mercury Species by Solid-Phase Microextraction GC-ICPMS
William Davis, Steven J. Christopher, Stephen E. Long, William R. Kelly
This preliminary technical note reports on the development of an on-line isotope dilution (ID) method that is applicable for the determination of inorganic and organic mercury species in marine samples. The method is demonstrated on NIST Standard Reference Material (SRM) 1566b Oyster Tissue, a well characterize natural material certified for both methylmercury and total mercury at (13.2 0.7) ng/g and (37.1 1.3) ng/g, which are much lower than most fresh water fish. The procedure involves microwave extraction of methyl and inorganic mercury species from the oyster tissue with acetic acid, followed by derivatization and headspace solid-phase microextraction (SPME) with a polydimethylsiloxane (PDMS)-coated silica fiber. The separated species from the gas chromatograph are mixed with the isotopic spike of enriched 201Hg that is continuously introduced as a gas via a gas liquid separator into the inductively coupled plasma mass spectrometer source. The isotopic spike level can be matched to the organic and inorganic mercury species for optimum ratios by changing the flow rate of the peristaltic pump. This method of quantification obviates the need for the species-specific isotopic spikes. Four different quantification methods based on peak height, peak area, flat sections of the chromatograms, and point-by-point ID determinations were evaluated and each yielded results for methyl, inorganic mercury, and total mercury in good agreement with the certified values. The results obtained demonstrate that on-line ID-SPME-GC-ICPMS is rapid and may become a robust alternative quantification scheme for the determination of mercury species at trace and ultra-trace levels in oyster tissue and other natural matrices.
inductively coupled plasma mass spectrom, isotope dilution, methylmercury, speciation
, Christopher, S.
, Long, S.
and Kelly, W.
On-line Isotope Dilution Determination of Mercury Species by Solid-Phase Microextraction GC-ICPMS, Analytical Chemistry
(Accessed December 9, 2023)