Thin layer chromatographic analysis of some common over the counter (OTC) cough–cold preparations

In the present study, potential utility of thin layer chromatography to differentiate some common OTC cough–cold preparations was evaluated. Twenty solvent systems were examined from which a solvent systems A comprising methanol:ammonia in the ratio of 100:1.5(v/v) and B comprising chloroform:methanol in the ratio of 90:10(v/v) were found to be most suitable as it showed a high degree of separation of different components of these preparations. It was also found that iodine fuming technique is the best visualizing method for examining the TLC chromatograms of these drug samples prior to subsequent instrumental analysis.