ANALYSIS OF DEMECLOCYCLINE BY CAPILLARY ELECTROPHORESIS

The analysis of demeclocycline and its main impurities by capillary el ectrophoresis is described. Demeclocycline is a tetracycline antibioti c. Main impurities are demethyltetracycline, 4-epidemeclocycline and 4 -epidemethyltetracycline, which are formed due to fermentation or degr adation. Method development was undertaken with a mixture consisting o f demeclocycline and its main impurities already mentioned. Using an u ncoated fused-silica capillary, the influence of buffer type, buffer p H and its concentration were systematically investigated. Non-ionic su rfactant Triton X-100 was added to the running buffer which greatly im proved separation selectivity. In all cases 1 mM EDTA was also added t o prevent metal ion complexation, Then capillary temperature and appli ed voltage were also optimized. UV detection was performed at 254 nm. A relative standard deviation of 1.0% was obtained for demeclocycline. The limit of detection was 0.3% (signal-to-noise ratio=3) and the lim it of quantification was 0.4% with respect to the original peak obtain ed with a solution containing 0.5 mg/ml demeclocycline.