The vector of calibration ratios: A simple transfer method for mass spectra

A robust method for reduction of instrument differences, the vector of calibration ratios, was developed to eliminate differences in unit resolution mass spectra of fatty acid methyl esters (FAME) caused by experimental conditions. Mass spectra of FAMEs were analyzed by two different mass spectrometers and after application of different tune procedures. The proposed method could remove 51–95% of the systematic difference in spectra caused by instrumental conditions. Highly similar spectra, which were incorrectly identified because of the contribution from experimental conditions, could be correctly identified after application of the calibration vector. The proposed method is simple, easy to implement and shows robustness when applied on spectra that is outside the range spanned by the calibration sample.