Effect of Buffer Constituents on Retention and Separation in Achiral and Chiral HPLC Systems with β-Cyclodextrin-Based Stationary Phase
Abstract
In HPLC, cyclodextrin-based stationary phases allow separation of both achiral and chiral analytes. Complexation of analytes into the cyclodextrin cavity is a very important part of the interaction mechanism.
However, possible complexation of buffer constituents must be also considered. This fact should not be overlooked in method development procedures.
In this study, β-cyclodextrinbased stationary phase (CYCLOBOND I 2000) was used, and two different buffers, namely aqueous solutions composed of lithium hydroxide/benzoic acid 10.0/24.5 mM, pH 4.00 and lithium hydroxide/acetic acid 9.9/60.0 mM, pH 4.01 of the same ionic strength were compared. Methanol was added as organic modifier in a methanol/buffer volume ratio 40/60.
The linear free energy relationship method was used for evaluation of interactions contributing to chromatographic performance of the separation system. Strong complexation of benzoic acid with cyclodextrin was obvious from the results.
This effect was clearly reflected in reduced retention and restricted (enantio) separation ability of the separation system containing benzoic acid in the buffer. On the other hand, complexing buffer constituents of mobile phases can offer a worthy alternative, to less "green"organic solvents, for reduction of the analysis time.