Capillary electrophoresis separation of sulphonamides and dihydrofolate reductase inhibitors

Abstract

Abstract. Twenty-two sulphonamides and three dihydrofolate reductase inhibitors (DHFR) were included in this study. At pH 7.5, eighteen drugs were resolved in 22 min. Above pH 7.5 the DHFR are not resolved and the pH range of 7-7.5 was found to be optimal. Around pH 7, where the degree of ionization of the SFA is highly variable, pK, and migration time are strongly correlated. Increasing phosphate buffer concentration from 25-100 mM generally improves resolution but increases analysis times. A good correlation between analyte mobility and the ratio of net charge to molecular weight indicates that this ratio may be used as a quick guide to the possibility of separation of related compounds. Our secondary objective was to compare the lead time and effectiveness of CZE with LC. It is clear that method development is much more rapid in CZE but with a sufficiently diverse group of compounds, CZE can be incapable of providing a full analysis without gradient control. Nonionized compounds are not separated at one extreme, and excessively mobile species may not emerge in a reasonable time, or, may migrate to the wrong electrode.

High Performance Liquid Chromatographic Analyses of Sulphonamides and Dihydrofolate Reductase Inhibitors. I. Separations in Methanol-Modified Solutions

“…These studies have also been reviewed,223 but many more recent publications have On the other hand, there have not been any investigations of instrumental methods for the broad screening for SFA and DHFR published since our capillary zone electrophoretic (CZE) work in 1993. 2 In this study it became apparent that conventional CZE (with the detector at the cathode) could not be successfully used to concurrently analyse for a wide range of SFA -or any other negatively charged compounds -if the span of pK, values is too great. At low pH, some compounds are unionised and inseparable from each other and the neutral marker, whilst others overcome the electroosmotic flow (EOF) and migrate in the wrong direction.…”

At-Line Solid-Phase Extraction Coupled to Capillary Electrophoresis: Determination of Amphoteric Compounds in Biological Samples

“…The cartridges were loaded with increasing volumes of a 10 lg/mL solution of the test compounds in pH buffer when using the C18 phase; analyte breakthrough was observed for pH F 5 (Figure 2). This can be explained by the negative charge of the test compounds at pH A 4 [9]. On the other hand, up to 8 mL of a solution of the analytes in a 10 mM phosphate buffer with pH varying from 3 to 8 could be loaded on the SDB cartridge without any breakthrough.…”

Analysis of sulfonamides by capillary electrophoresis

“…In a paper by Ricci and Cross [35], a method for twentytwo sulfonamides and three dihydrofolate reductase (DHFR) inhibitors was described. Using a BGE with pH 7.5, 18 drugs were resolved in 22 min.…”