Predicting retention data using the slope of the log adjusted retention time vs. carbon number plot for n-alkanes

Summary The slope of the n-alkane log plot dt′_R/dn_c (t′_R=adjusted retention time; n_c=carbon number) for a stationary phase can be used to obtain the retention index of an unidentified substance in a chromatogram containing only one peak with a known retention index, or to predict the retention time of a substance from that of a different homolog in the same series. It can also be used to translate retention indices into relative retention time, partition coefficient or specific retention volume. Published values of the slope are collected and critically evaluated. Equations are deduced that predict its approximate value at a specified temperature given the value at only one other temperature.