Fig. 1.

An example of improved peak annotation by MetAssign. The peak at m/z = 167.996769 has two possible database matches, l-Cysteate (which is known to be in the sample) and 6-Chloro-1-hydroxybenzotriazole (which is known not to be in the sample). The prior likelihood of choosing l-Cysteate over 6-Chloro-1-hydroxybenzotriazole is 17 over 83%, and by a nearest match criterion, the later would be selected. However, in the posterior, the ratios change to 92 over 8%, as the MetAssign algorithm detects the confirming presence of the sulphur-34 isotope peaks in the same cluster