High-precision measurements of17O/16O and18O/16O of O2 and O2/Ar ratio in air

A method for high-precision and high-accuracy mass spectometric measurements of the ratios among the three oxygen isotopes, and of the O2/Ar ratio, is presented. It involves separation of the O2-Ar mixture from air and includes a fully automated system that ensures highly reliable sample processing. Repeated measurements of atmospheric oxygen yield the repeatability (±SE × t, standard error of the mean (n = 12) multiplied by Student's t-factor for a 95% confidence limit) of 0.004, 0.003 and 0.2‰ for δ18O, δ17O and δO2/Ar, respectively. Copyright © 2003 John Wiley & Sons, Ltd.