Chemometric methods to classify stationary phases for achiral packed column supercritical fluid chromatography

This paper investigates classification models for packed columns used in supercritical fluid chromatography (SFC). Forty‐eight columns of varied stationary phase chemistries available on the market are evaluated. The retention factors of 134 selected test compounds are used to compute hierarchical cluster analysis (HCA), principal component analysis (PCA), and quantitative structure–retention relationships (QSRRs). The use of HCA in conjunction with either PCA of QSRRs provides a classification of columns that is consistent with the experience of the SFC chromatographer. Besides, different coefficients, namely, Pearson correlation coefficient (r), selectivity difference (s2), distance (L), and angle (θ), were calculated between all couples of columns to identify a ranking index, which would provide meaningful information whenever two columns need to be compared on an objective basis. This can be the case either when an equivalent is sought for replacement of a reference column or when an orthogonal column is desired to achieve complementary selectivity. It is concluded that the θ angle and the normalized distance L/u are the best coefficients, allowing for a meaningful comparison between two columns. Copyright © 2012 John Wiley & Sons, Ltd.