Validation of a simple method for the determination of oxytetracycline in ointment by non-aqueous capillary electrophoresis

A non-aqueous capillary electrophoresis method for the determination of oxytetracycline in an ointment have been validated. The oxytetracycline (OTC) is separated from related impurities and degradation products as metal chelates with magnesium ions. Thus, the method show high selectivity. The sample preparation is performed as a single extraction step of OTC from the melted ointment. The test for linearity in the range from 0.2-3.0 mg ml(-1) gave a straight line with a coefficient of correlation greater than 0.999. Precision and accuracy were investigated using standard addition at three different concentration levels and six separate determinations at each level. The precision is good and may be expressed as the coefficient of variation which was lesser than 3.6%. The recovery is close to 100%. (C) 1997 Elsevier Science B.V.