Analysis of macrolide antibiotics by capillary electrophoresis

Capillary electrophoresis was utilized in the study of the macrolide antibiotics (i.e. pharmaceutical glycoconjugates) clarithromycin, erythromycin, oleandomycin, troleandomycin, and spiramycin. In order to assist in analyte solubilization, two buffer systems using acetonitrile were developed. The first system involved 30 mM sodium cholate and 20% acetonitrile in 80 mM sodium phosphate, pH 6. This buffer permitted the baseline resolution of all five glycoconjugated antibiotics. In addition, erythromycin was separated from its derivatives estolate and ethylsuccinate. In the absence of surfactants, a higher acetonitrile quantity, 65%, was used in the second buffer system, with 35 mM sodium phosphate, pH 6. Selectivity between oleandomycin and clarithromycin was reversed in this system compared to the cholate buffer, indicating solute interaction with the cholate micelles in the previous system. Calibration linearity and detection sensitivity were improved in the high acetonitrile buffer, due to decreased background absorbance. It was demonstrated that both buffer systems can be utilized for the visualization of minor components that may be present in bulk pharmaceuticals.