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USGS · 70019383

Resolution of matrix effects on analysis of total and methyl mercury in aqueous samples from the Florida Everglades

M.L. Olson·L.B. Cleckner·J.P. Hurley·D. P. Krabbenhoft·T.W. Heelan
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Abstract

Aqueous samples from the Florida Everglades present several problems for the analysis of total mercury (HgT) and methyl mercury (MeHg). Constituents such as dissolved organic carbon (DOC) and sulfide at selected sites present particular challenges due to interferences with standard analytical techniques. This is manifested by 1) the inability to discern when bromine monochloride (BrCl) addition is sufficient for sample oxidation for HgT analysis; and 2) incomplete spike recoveries using the distillation/ethylation technique for MeHg analysis. Here, we suggest ultra-violet (UV) oxidation prior to addition of BrCl to ensure total oxidation of DOC prior to HgT analysis and copper sulfate (CuSO 4 ) addition to aid in distillation in the presence of sulfide for MeHg analysis. Despite high chloride (Cl - ) levels, we observed no effects on MeHg distillation/ethylation analyses.

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M.L. Olson, L.B. Cleckner, J.P. Hurley, D. P. Krabbenhoft, T.W. Heelan. 1997. Resolution of matrix effects on analysis of total and methyl mercury in aqueous samples from the Florida Everglades. https://doi.org/10.1007/s002160050435

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USGS2001

An interlaboratory study to test instrument performance of hydrogen dual-inlet isotope-ratio mass spectrometers

An interlaboratory comparison of forty isotope-ratio mass spectrometers of different ages from several vendors has been performed to test 2 H/ 1 H performance with hydrogen gases of three different isotopic compositions. The isotope-ratio results (unsufficiently corrected for H 3 + contribution to the m/z = 3 collector, uncorrected for valve leakage in the change-over valves, etc.) expressed relative to one of these three gases covered a wide range of values: –630‰ to –790‰ for the second gas and –368‰ to –462‰ for the third gas. After normalizing the isotopic abundances of these test gases (linearly adjusting the δ values so that the gases with the lowest and highest 2 H content were identical for all laboratories), the standard deviation of the 40 measurements of the intermediate gas was a remarkably low 0.85‰. It is concluded that the use of scaling factors is mandatory for providing accurate internationally comparable isotope-abundance values. Linear scaling for the isotope-ratio scales of gaseous hydrogen mass spectrometers is completely adequate.

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