A major issue in optimizing the resolving power of two-dimensional chromatographic separations is the choice of the two phases so as to maximize the distribution of the analytes over the separation space. In this work, we studied the choice of appropriate reversed phases to use in on-line comprehensive two-dimensional liquid chromatography (. LC×. LC). A set of four chemically different conventional bonded reversed phases was used in the first dimension. The second dimension column was either a conventional bonded C18 phase or a carbon-clad phase (CCP). The LC×LC chromatograms and contour plots were all rather similar indicating that the selectivities of the two phases were also similar regardless of the reverse phase column used in the first dimension. Further, the spatial coverage seen with all four first dimension stationary phases when paired with a second dimension C18 phase were low and the retention times were strongly correlated. However, when the C18 column was replaced with the CCP column much improved separations were observed with higher spatial coverages, greater orthogonalities and significant increases in the number of observed peaks.
Bibliographical noteFunding Information:
The authors of this work gratefully acknowledge the × National Science Foundation ( CHE 1213561 ) for providing funds for this work. The authors would also like to thank Agilent Technologies, Inc. for providing the columns and base silica for the CCPs as well as the 1290 LC LC system. Appendix A
© 2014 Elsevier B.V.
- Carbon-clad phase
- Column selection
- Comprehensive two dimensional liquid chromatography (LC×LC)
- Hydrophobic subtraction model
- Method development
- Reverse phase