Simultaneous spectrophotometric determination of aspirin, acetaminophen and ascorbic acid in pharmaceutical preparations

A simple and rapid first derivative spectrophotometric procedure has been d eveloped for the simultaneous determination of a three component mixture co mposed of aspirin, acetaminophen and ascorbic acid, without the necessity f or the previous separation of any component. In this method, the absorbance ratio technique was used in the first derivative spectra of the compounds. The first two components have a characteristic absorbance in their first d erivative spectra (219.3 and 262.5 nm) and they were determined directly by solving the absorbance ratio equation. Ascorbic acid was assayed by subtra cting the concentration of aspirin and acetaminophen from the total concent ration of the mixture which was calculated from the values belonging to the common isoabsorptive point (221.8 nm) in the first derivative spectrum. Th e procedure was applied successfully to the analysis oi commercial tablets and also compared with an HPLC method.