Identification and separation of five cephalosporins by micellar electrokinetic capillary chromatography.

The cephalosporins are a group of structurally related, broad spectrum beta-lactam antibiotics isolated from the mold Cephalosporium. Methods of analysis of cephalosporin antibiotics include microbiological, titrimetric and chromatographic assays. Chromatographic techniques, including high-performance liquid chromatography, have been extensively utilized for specific and sensitive assays of beta-lactam antibiotics in a variety of matrices, i.e. clinical and pharmaceutical. Several of the drawbacks of HPLC in the analysis of cephalosporins in food and biological samples include matrix interferences and low resolution due to column adsorption. Recently, the applicability of capillary electrophoresis to the resolution of beta-lactam antibiotics has been demonstrated in the literature. In this paper we employed sodium borate and an anionic surfactant, sodium dodecyl sulfate (SDS), in a separation technique called micellar electrokinetic capillary chromatography with UV detection, to resolve a mixture of five cephalosporins--cefuroxime, cephalexin, cephapirin, cefamandole nafate and cephalothin. The presence of SDS in the running buffer above the critical micelle concentration, creates a pseudostationary phase enabling high-efficiency chromatographic separations. The effect of the ion-pairing reagent, pentanesulfonic acid sodium salt, on the resolution of the cephalosporin mixture in conjunction with SDS was also examined.