Simultaneous quantitation of tobramycin and colistin sulphate by HPLC with evaporative light scattering detection

A rapid and simple method for the simultaneous determination of tobramycin and colistin sulphate in a pharmaceutical formulation by reversed phase HPLC and evaporative light scattering detection is described. Chromatographic separation was carried out in gradient mode using a Zorbax SB C18 column (150mmx4mm, 3.5microm) with mobile phases of acetonitrile and water containing trifluoroacetic at 1ml/min. The method was validated using methodology described by the International Conference of Harmonization. The method was shown to be specific, precise, accurate and linear. Real samples were analyzed to demonstrate the applicability of the chromatographic method in a routine use.