Peak deviations before and after alignment. Retention-time deviations of matched peaks are color-coded in these two panels, before (top) and after (bottom) application of the described alignment method. The heat-map code is displayed to the right (Note the narrower range of deviations represented by colors in the lower panel). White cells represent instances where a peak in a run either was not detected or did not pass signal-to-ratio and peak-width criteria. Twenty-one peaks were omitted from the display because they met criteria in fewer than ten sample runs; their inclusion does not alter the result. Run #8 again was selected as the alignment reference. Several weeks, and a GC-MS re-tuning operation, occurred between runs 17 and 18.