Optimization and validation of a new HPLC method using monolithic column for simultaneous determination of pentoxifylline and related compounds

A new high performance liquid chromatography (HPLC) method for the simultaneous determination of pentoxifylline and its main related substances – theophylline, theobromine and caffeine – in pharmaceuticals has been developed. Chromatographic separation was achieved within 5 min on a monolithic column eluted with a mobile phase consisting of methanol – water (35/65 v/v) mixture in an isocratic mode at a flow rate of 1 mL/min. The detection wavelength was set at 272 nm. The proposed method was validated over a concentration range of 0.5 – 14 μg/mL for pentoxifylline and 0.1 – 3.0 μg/mL for the related impurities. Calibration plots were linear for pentoxifylline and all other compounds with a correlation coefficient greater than 0.99. Relative variation coefficients for reproducibility and repeatability were below 2.0%. Recoveries from standard addition assay of an individual component in pharmaceutical formulations varied from 95.0% to 102.9%. The proposed method was successfully applied for the determination of pentoxifylline, theophylline, theobromine, and caffeine in pharmaceutical formulations (tablets and injections). Recoveries with respect to label amount in pharmaceutical formulations varied from 94.0% to 105.9%.