Deviation Δppmof peptide masses from mass cluster centres predicted using the Equation 24 in parts per million [ppm]. Gray line – moving average of Δppm. Orange lines – Standard deviation of Δppm, Green lines – 1% and 99% Quantile computed for mass windows having a size of 15Da and covering the mass range. Magenta dot dashed line – maximum possible deviation from cluster centre, which can be assigned to the true cluster centre using the Equation 30. Horizontal dotted blue line – distance of DHB (2,5-dihydroxybenzoic acid) matrix clusters from the peptide mass cluster centres; dashed line – distance of alphacyano (alpha-Cyano-4-hydroxycinnamic acid) clusters from the peptide mass cluster centres; distance of sinapicacid (3,5-Dimethoxy-4-hydroxycinnamic acid) clusters from peptide mass cluster centres.