Journal of Pharmaceutical and Biomedical Analysis vol:58 pages:49-57
A method was validated and optimized to determine tobramycin (TOB) and its related substances. TOB is an aminoglycoside antibiotic which lacks a strong UV absorbing chromophore or fluorophore. Due to the physicochemical properties of TOB, capillary electrophoresis (CE) in combination with Capacitively Coupled Contactless Conductivity Detection (C(4)D) was chosen. The optimized separation method uses a background electrolyte (BGE) composed of 25mM morpholinoethane-sulphonic acid (MES) adjusted to pH 6.4 by l-histidine (l-His). 0.3mM cetyltrimethyl ammonium bromide (CTAB) was added as electroosmotic flow modifier in a concentration below the critical micellar concentration (CMC). Ammonium acetate 50mgL(-1) was used as internal standard (IS). 30kV was applied in reverse polarity (cathode at the injection capillary end) on a fused silica capillary (65/43cm; 75μm id). The optimized separation was obtained in less than 7min with good linearity (R(2)=0.9995) for tobramycin. It shows a good precision expressed as RSD on relative peak areas equal to 0.2% and 0.7% for intraday and interday respectively. The LOD and LOQ are 0.4 and 1.3mgL(-1) corresponding to 9pg and 31pg respectively.