Figure 4. Relative abundance of m/z 17-21, together with the results from the fit from one injection with 18O water. On this scale, the small error bars (around 10-4) are not visible. On top, residuals from the true signal with respect to the fitted signal of QMS (m/z 17-21) are shown. The error bars are the standard deviations from 14 separate injections.
As a proof-of-method the enriched H218O water was diluted with (approximately) 1 and 2% water with 18O at natural abundance. The expected differences in 18O abundances between these dilutions and the not diluted enriched water based on weights, are shown in Table 1. The measured (fitted)18O abundances and the expected 18O abundances are within 0.03% of each other. We concluded that real (small) differences in abundances are correctly measured.
<Table 1>