Mass Defect Filter for Removing Noise and Detector Oscillation Artifacts in Centroided Time-of-Flight Mass Spectra

Spurious peaks in centroided mass spectra resulting from detector oscillation or "ringing" can be identified by their unusual mass defects. Mass defect plots (fractional m/z vs measured m/z) for the single-charge mass spectrum of a pure compound show data points falling along lines with well-defined slopes. Detector oscillation and electronic noise peaks were removed from database spectra of pure compounds and mixtures by eliminating points outside two standard deviations of the slope of the major peaks. No loss of chemical information was observed, even for compounds with isobaric fragment peaks.