High Efficiency Separation Techniques: Fast HPLC Using Monolithic Silica Columns and Chiral Separation Using Capillary Zone Electrophoresis

Abstract

A possible tool for converting a standard LC method to a fast LC method is the use of monolithic silica columns. From our studies comparing conventional particle-packed to monolithic silica columns we have concluded that methods for the small drug molecules were successfully transferred. For the relatively larger molecule insulin, the method was not completely transferred from conventional to monolithic column at first go. However, optimization by slightly decreasing the percentage of organic modifier in the mobile phase was sufficient for a good resolution on the monolithic column. Good precision and column to column reproducibility have been obtained for monolithic columns. The most important advantages of developing methods with monolithic silica columns include the ability to save time for finding initial separation conditions or further optimization of selected conditions. This is due to the applicability of high flow rates and so shorter run and equilibrium times. Monolithic columns have also shown to be advantageous in developing methods for complex mixtures, by connecting two or more columns together to increase the separation efficiency. On the other hand, enantiomeric separation by capillary electrophoresis has been investigated. Initial selections of the best cyclodextrin for the chiral separation of ten tested basic compounds have been done using a proposed screening strategy and based on the measured resolution. For the tested compounds satisfactory initial enantiomeric separations have been obtained. This approach can also be used to test a broad range of chiral compounds including basic and neutral compounds. It was observed that negatively charged CDs gave better results compared to the neutral CDs. Furthermore, they gave a better enantiomeric separation of the basic drugs when applied under reversed polarity due to stronger interaction with the positively charged analytes.