Development and validation of a generic RP‐HPLC PDA method for the simultaneous separation and quantification of active ingredients in cold and cough medicines

A novel generic reverse phase high performance liquid chromatography (RP‐HPLC) method is developed and validated for simultaneous determination of seven pharmaceutically active ingredients, namely, acetaminophen, dextromethorphan, doxylamine, phenylephrine, guaifenesin, caffeine and aspirin. All seven ingredients were quantified in soft gel, syrup and tablet formulations of the over‐the‐counter US‐marketed products, as per the guidelines of the International Conference on Harmonization. The separation was achieved in a 16 min run time on an Agilent Zorbax Phenyl column using a gradient method with two mobile phases. Mobile phase A was 0.15% trifluoro acetic acid in purified water and while mobile phase B was a mixture of acetonitrile and methanol (750:250 v/v) with 0.02% trifluoro acetic acid. The flow rate was 1.0 mL min −1 and injection volume was 10 μL. Detection was performed at 280 nm using a photodiode array detector. As part of the method validation, specificity, linearity, precision and recovery parameters were verified. The concentration and area relationships were linear ( R 2  > 0.999), over the concentration ranges 20–120 μg mL −1 for acetaminophen, 75–450 μg mL −1 for dextromethorphan, 31.25–187.5 μg mL −1 for doxylamine, 25–150 μg mL −1 for phenylephrine, 25–150 μg mL −1 for aspirin, 6.5–39 μg mL −1 for caffeine and 12–72 μg mL −1 for guaifenesin. The relative standard deviations for precision and intermediate precision were <1.5%. The proposed RP‐HPLC generic method is applicable for routine analysis of cold and cough over‐the‐counter products.