Identification of Degradation Products and a Stability-Indicating RP-HPLC Method for the Determination of Flupirtine Maleate in Pharmaceutical Dosage Forms

In this stability-indicating, reversed-phase high-performance liquid chromato-graphic method for flupiritine maleate, forced degradation has been employed and the formed degradants were separated on a C₁₈ column with a 80:20% v/v mixture of methanol-water containing 0.2% (v/v) triethylamine; the pH was adjusted to 3.1. The flow rate was 1 mLmin−1 and the photodiode array detection wavelength was 254 nm. Forced degradation of the drug was carried out under acidic, basic, thermal, photolytic, peroxide, and neutral conditions. Chromatographic peak purity data indicated no co-eluting peaks with the main peaks. This method resulted in the detection of seven degradation products (D1–D7). Among these, three major degradation products from acidic and basic hydrolysis were identified and characterized by ¹H-NMR, ¹³C-NMR, and mass spectral data. The method was validated as per International Conference on Harmonization guidelines (Q2). The linearity of the method was in the concentration range of 20–120 μgmL⁻¹. The relative standard deviations for intra- and interday precision were below 1.5%. The specificity of the method is suitable for the stability-indicating assay.