ABSTRACT
A mixture of acetaminophen, diphenhydramine hydrochloride and pseudoephedrine hydrochloride is used for the symptomatic treatment of common cold. In this study, a derivative spectrophotometric method based on zero-crossing technique was proposed for simultaneous determination of acetaminophen, diphenhydramine hydrochloride and pseudoephedrine hydrochloride. Determination of these drugs was performed using the [1]D value of acetaminophen at 281.5 nm, [2]D value of diphenhydramine hydrochloride at 226.0 nm and [4]D value of pseudoephedrine hydrochloride at 218.0 nm. The analysis method was linear over the range of 5-50, 0.25-4, and 0.5-5 microg/mL for acetaminophen, diphenhydramine hydrochloride and pseudoephedrine hydrochloride, respectively. The within-day and between-day CV and error values for all three compounds were within an acceptable range [CV<2.2% and error<3%]. The developed method was used for simultaneous determination of these drugs in pharmaceutical dosage forms and no interference from excipients was observed