A VALIDATED STABILITY-INDICATING AND LC-MS COMPATIBLE METHOD FOR THE DETERMINATION OF RELATED SUBSTANCES AND ASSAY OF MONTELUKAST SODIUM AND LEVOCETIRIZINE HCL BY U-HPLC IN TABLET DOSAGE FORM

A novel gradient reverse-phase ultra-high performance liquid chromatography (U-HPLC) method has been developed and validated for determination of related substances and assay of Montelukast sodium and Levocetirizine HCl in 4 mg Montelukast sodium and 2.5 mg Levocetirizine HCl tablet. The separation of both drugs from their related impurities has been successfully achieved using Kinetex, Phenyl-Hexyl (100°A,150x4.6 mm, 5µm) column maintained at 20 oC±2oC. Flow rate was optimized at 1.2 ml/min. The wavelength was fixed at 230 nm with injection volume of 20 µl. Sensitivity, linearity, establishment of relative response factor, limit of quantitation and forced degradation were performed as part of suitability of the method. The gradient programme of this method was checked in mass analysis of all impurities and both drugs as U-HPLC parameter with mass parameters to study the compatibility of the method in mass analysis. Assay method was also developed using same column, flow rate and injection volume. But here, runtime was shorter with higher column oven temperature (30 oC±2oC). Specificity, accuracy, linearity, precision and solution stability of standard, sample and mobile phase were determined as part of validation. Filter variability in assay method was evaluated through determining similarity factor between assay values of unfiltered and PVDF with nylon. Key Words: Reverse-phase U-HPLC, gradient programme, related substances, LC-MS, assay, method development, validation