Analysis of spiramycin by capillary electrophoresis

The development and validation of an analytical method for the determinatio n of spiramycin I in the presence of its related substances by capillary el ectrophoresis is shown. The separation, performed in a phosphate buffer (80 mM, pH 7.5) containing 12 mM cetyltrimethylammonium bromide (CTAB) and 20 mM sodium cholate, with a 50 mu m ID and 44 cm long fused-silica capillary (36 cm effective length), applying a voltage of 12 kV (1 similar to 80 mu A ), at 25 degrees C, is achieved in 15 min. Good selectivity among spiramyci n I and its related substances was obtained. The influence of the buffer pH , and of the CTAB and sodium cholate concentrations was investigated. The m ethod robustness, examined by means of a full-fraction factorial design, sh ows that it can be used within the limits set for the three parameters that were investigated. The method is linear(r = 0.9992) and precise (day-to-da y corrected peak area repeatability, n = 18, relative standard deviation = 1.3%). The limits of detection and quantitation are 7 pg (0.025%) and 22 pg (0.08%), respectively, relative to a 2 mg/mL solution.