3. RESULTS
The 18O characterization of our 6 different highly enriched 18O waters were carried out by measuring QMS spectra and fitting those spectra. As described in section 2.3.1, m/z signals 17-21 from the QMS spectra were used for this spectral fitting method. In Figure 4 an integrated true measured QMS signal from m/z 17-21 and the fitted signal from the bespoke program are compared, their very small residuals (in the order of 10 ppm) are shown on top panel of the figure. These residuals show that the fitted signals are in excellent agreement with the measured signals. The displayed error bars are the standard deviations of 14 measurements.
<Figure 4>