A qualitative informational similarity technique has been used to describe the informational orthogonality of projected two-dimensional (2-D) chromatographic separations of complex mixtures from their one-dimensional 1-D separations. The reversed-phase liquid chromatography (RPLC), supercritical fluid chromatography (SFC), gas-liquid chromatography (GLC), and micellar electrokinetic capillary chromatography (MECC) retention behavior of up to 46 solutes of varying molecular properties was studied by 2-D range-scaled retention time plots and information entropy calculations. One hundred five combinations of technique/stationary phase pairs were used to simulate the 2-D chromatographic analyses. The informational entropy of one and two dimensions, the mutual information, the synentropy or "cross information", and the informational similarity were calculated to describe the informational orthogonality. In addition, pattern descriptors were used to qualitatively describe the 2-D peak distribution. With the solutes tested, informational orthogonality, zero informational similarity, was observed with MECC-SDS/SFC-C1, MECC-SDS/SFC-Carbowax, MECC-TTAB/SFC-Carbowax, HPLC-C18/GLC-DB-5, HPLC-PBD/SFC-phenyl, SFC-Carbowax/GLC-DB5, and HPLC-phenyl/SFC-phenyl 2-D chromatographic systems. Conversely, with the solutes tested, informational nonorthogonal behavior described by range-scaled retention time plots to moderate to severe band overlap and data clustering was observed with 2-D chromatographic systems with high informational similarity and moderate to high degrees of synentropy. These results should prove useful for predicting complementary 2-D techniques as well as for choosing a second separation technique for confirmation of separation or peak purity.

No abstract

No abstract

Using predictions based on results obtained from Information Theory and Factor Analysis for the two-dimensional separation of a complex isomeric mixture, a practical experimental comprehensive coupled reversed phase-reversed phase chromatographic system was developed. In total four reversed phase-reversed phase systems were studied, each of which theory predicted would be able to resolve essentially equal numbers of components. However, in practice only one of these coupled systems realised the theoretical potential. This system employed as the first dimension, a C18 stationary phase with methanol as the mobile phase and as the second dimension, carbon clad zirconia as the stationary phase and acetonitrile as the mobile phase. In this system, 27 of the 32 isomers of a mixture of oligostyrenes were resolved. Failure of the remaining coupled systems to achieve the theoretical potential was attributed to high solute crowding, low efficiency of separation space utilisation and long analysis times in the second dimension.