Laser-based stable hydrogen and oxygen analyses: How reliable can measurement results be?

摘要: A comparison of stable hydrogen and oxygen isotope-ratio analyses by dual inlet mass spectrometry (IRMS) laser absorption indicates that laser-based filtered, low salinity, environmental waters can be substantially biased. For example, the IRMS δH values a Mississippi River sample collected November 26, 2007 at Thebes, Illinois were –49.6 ± 0.2 h (N = 2) –36.8 0.9 6), respectively, which differ more than 12 hĊomparative δO for measurements are –7.04 0.08 –0.58 0.14 6 hĖven larger differences 14.5 7.8 determined from December 19, 2007. Of comparative wide variety ground-water, surface-water, precipitation, tap-water samples (total 588), 5 differed 3 hĖach was measured least twice both techniques on different days. these samples, 2 as described above ground-water wastewater sites or contaminated with organic wastes. 403 water days, 14 0.40 1 hṪhese three sites, including two above, all surface-water network in autumn winter. Nevertheless, majority small. 90 percent difference is less 0.3 hṪhe between results appear to due primarily bias caused dissolved carbon (DOC). Addition activated granules prior analysis absorbs DOC improves agreement measurement techniques, but addition has yet become common practice isotope community. Samples analyzed using only might yield inaccurate results.