Abstract
Two simple, rapid chromatographic methods were developed for the simultaneous determination of Theophylline (THP), Guaifenesin (GUI) and Guaifenesin impurity namely Guaiacol (GUA). The first method is an isocratic reversed-phase high-performance liquid chromatography (RP-HPLC) method, where separation of THP, GUI and GUA was achieved on C-18 column using methanol: water (containing 0.1% triethylamine): acetonitrile (30:60:10, by volume) as a mobile phase with a flow rate of 0.7 mL/min and UV detection at 275 nm. The separation was achieved at retention times (R-t 3.76, 6.76 and 8.79 for THP, GUI and GUA, respectively). The calibration plots were linear over the concentration range of 2-25, 2-37 and 0.5-10 mu g/mL for THP, GUI and GUA, respectively. The second method is high pressure thin layer liquid chromatography method, which was developed using silica gel plates 60F(254) as a stationary phase with ethyl acetate: hexane: methanol: ammonia (65:35:10:2, by volume) as a developing system. The densitometric measurements were performed at 275 nm with good R-f values (0.13, 0.35 and 0.8) for THP, GUI and GUA, respectively. The calibration plots showed good correlation over the range (0.4-2 mu g/band) for both THP and GUI, and (0.4-1.2 mu g/band) for GUA. The two proposed methods were validated according to ICH guidelines. The results for the two methods were statistically compared to those obtained by a reported high-performance liquid chromatography method and no significant difference was found regarding accuracy and precision.