[Separation of drugs cephalexin, ampicillin, and their biosynthetic precursors L-Phe-L-Cys-D-Val and D-Phe-L-Cys-D-Val by capillary zone electrophoresis].
The separation of drugs cephalexin, ampicillin and their biosynthetic precursors L-Phe-L-Cys-D-Val and D-Phe-L-Cys-D-Val was investigated by using capillary zone electrophoresis in acidic Tris-H3PO4 buffer at pH 2.3. With 50 mmol/L Tris-H3PO4 (pH 2.3) buffer, L-Phe-L-Cys-D-Val and D-Phe-L-Cys-D-Val were only partially separated whereas near baseline separation was achieved between cephalexin and ampicillin. The experiments showed that the addition of beta-type cyclodextrins (beta-CD) to the running buffer can influence the separation selectivity. When beta-CD was used as buffer additives at 12 mmol/L, the separation between L-Phe-L-Cys-D-Val and D-Phe-L-Cys-D-Val was much improved, however, the separation between cephalexin and ampicillin was impaired. When using 50 mmol/L Tris-H3PO4 containing 12 mmol/L DM-beta-CD (pH 2.3) buffer system, all compounds investigated were completely separated. This separation method is simple, fast and easy to operate. It involves only the conventional reagents with a much lower run cost than using HPLC. It is expected to be used in the synthetic process monitoring.