A new stability-indicating HPLC-UV method for determination of amlodipine besylate and its impurities in drug substance

A new fast stability-indication high performance liquid chromatography method was developed and validated for the determination of amlodipine besylate and its organic impurities in drug substance. The separation of amlodipine and its seven impurities was achieved on a core shell C18 column, 100 mm × 4.6 mm; 2.6 μm, within 15 min. The mobile phase comprised of 0.4% ammonium hydroxide in water and methanol delivered in a gradient mode; the method detection wavelength is 237 nm. The selected column is stable at high pH and provided a good peak shape for basic compounds. Amlodipine besylate was subject to acid, base, oxidative, thermal, and photolytic stress conditions. The degradation products were well resolved from the amlodipine peak and its impurities. Major degradants were analyzed by liquid chromatography coupled with single-quadrupole mass detector. Amlodipine peak was shown to be free of co-elution by mass spectral analysis in all stress conditions. The method was validated in terms of specificity, linearity, accuracy, precision, and robustness. The developed method could be applied for routine quality control analysis of amlodipine besylate drug substance.