GC-FID data formats.

<p><b>A.</b> Three hypothetical chromatograms are shown corresponding to samples A, B and C. Integrated peaks (filled areas) are annotated with retention times and peak heights. <b>B.</b> Using proprietary software (see main text), retention times and quantification measures like the peak height can be extracted and written to a peak list that contains sample identifiers (’Sample_A’, ‘Sample_B’ and ‘Sample_C’), variable names (’retention_time’ and ‘peak_height’) and respective values. Computations described in this manuscript use a retention matrix as the working format.