Journal of Chromatography A vol:740 issue:1 pages:119-123
The analysis of demeclocycline and its main impurities by capillary electrophoresis is described. Demeclocycline is a tetracycline antibiotic. Main impurities are demethyltetracycline, 4-epidemeclocycline and 4-epidemethyltetracycline, which are formed due to fermentation or degradation. Method development was undertaken with a mixture consisting of demeclocycline and its main impurities already mentioned. Using an uncoated fused-silica capillary, the influence of buffer type, buffer pH and its concentration were systematically investigated. Non-ionic surfactant Triton X-100 was added to the running buffer which greatly improved separation selectivity. In all cases 1 mM EDTA was also added to prevent metal ion complexation, Then capillary temperature and applied 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 limit of quantification was 0.4% with respect to the original peak obtained with a solution containing 0.5 mg/ml demeclocycline.