Validated stability-indicating HPLC method for the separation of pindolol enantiomers and its related substances

A simple, rapid and stability-indicating reverse-phase liquid chromatographic (RP-LC) method was developed for the separation of pindolol (PDL) and its related substances in the presence of its degradation products generated from forced decomposition studies. The chromatographic separation was achieved on a C18 Inertsil ODS-3V column (250 mm x 4.6 mm i.d.), using a mobile phase of 20 mM sodium dihydrogen orthophosphate-acetonitrile containing orthophosphoric acid to maintain pH at 4.0. Gradient elution was used at a flow rate of 1.0 mL/min. The UV detector was operated at 205 nm and the column temperature was maintained at ambient. Separation of PDL enantiomers was achieved on normal phase liquid chromatography (NP-LC) using a chiral pack AD-H (250 mm x 4.6 mm i.d.) column, with mobile phase consisting of n-hexane : ethanol : diethylamine (860 : 140 mL : 0.05%, v/v). A flow rate of 0.9 mL/min and detection wavelength of 215 nm were used. The method was validated for specificity, linearity and range, precision, accuracy, solution stability, robustness, limit of detection (LOD) and limit of quantification (LOQ). Selectivity of the RP-LC method was validated by subjecting the stock solution of PDL to acidic, basic, photolysis oxidative and thermal degradation. The calibration curve was found to be linear in the concentration range of 0.01 - 100 μg/mL (r = 0.9998) and 0.001 - 50 μg/mL (r = 0.9982) of PDL for the RP-LC and NP-LC method, respectively. The peaks of degradation products did not interfere with that of pure PDL. The utility of the developed method was examined for chemical and chiral purity by analyzing the tablets containing PDL and also by determining the related substances of PDL. The results of analysis were supported by statistical parameters.