Development and validation of a novel LC/ELSD method for the quantitation of gentamicin sulfate components in pharmaceuticals.

摘要

The equivalent response of evaporative light scattering detector (ELSD) for compounds of similar structure is exploited to develop an LC/ELSD method for the simultaneous quantitation of the four main components of gentamicin sulfate, using as external standard the one main component kanamycin. A C(18) column was used along with a mobile phase consisting of H(2)O (containing 35.4microg/ml of trichloroacetic acid and 0.89microl/ml of trifluoroacetic acid)-methanol-acetonitrile (990:5:5, v/v/v), in an isocratic mode at 1.1ml/min. Parameters of ELSD were 50 degrees C for evaporation temperature and 3.0bar for pressure of carrier gas (N(2)). A logarithmic calibration curve was obtained for sulfate (t(R) = 1.9min) from 4.2 to 150microg/ml (r > 0.994) with a precision of 0.18%R.S.D. Kanamycin and the four gentamicin components (C(1a), C(2), C(2a) and C(1)) were eluted at 3.2, 4.6, 5.9, 7.1 and 8.7min, respectively, with good resolution (Rs > 1.5). Logarithmic calibration curve was obtained for each component (r > 0.99) with statistically equal slopes varying from 2.457 to 2.558. The mass range of total gentamycin was 35-240microg/ml. The proposed method was applied for the determination of gentamicin components and sulfate in raw materials and pharmaceutical formulations (injection, drops and cream) without any pretreatment except cream, for which liquid-liquid extraction was required. Recovery from standard addition experiments in commercial formulations was 99-100% regarding total gentamicin and 89-108% regarding individual components, with a precision (%RSD, n = 4) 0.7-5.8%.