Cluster and principal component analysis for Kováts’ retention indices on apolar and polar stationary phases in gas chromatography

An extended set of Kováts’ retention indices of 137 organic compounds obtained at 405.15 K with C 78 standard alkane and with standalone polar interactive groups was analyzed. The retention data determined using gas chromatography were subjected to hierarchical cluster analysis and principal component analysis to detect structure in the data and to classify retention indices and solutes alike. The statistical evaluation of the retention data explored the correlation between the retention indices of the solutes and the similarities/differences of the stationary liquids. A set of chromatographic systems was selected as possible new standards relating to linear solvation energy relationships based on the chemometric data reduction. The new molecular descriptors based on retention indices were tested in correlation models for normal boiling point and olive oil/gas partition coefficient data using ridge regression. The ridge regression provided new ways for variable selection. The normal boiling points of organic compounds can reasonably be described using retention indices on apolar (C78) and polar (trifluoro, hydroxy, bromo and cyano) model compounds. The partition coefficients between olive oil and the gas phase can similarly be well correlated with retention indices on apolar (C78) and polar (tetramethoxy, trifluoro and hydroxy) model compounds.