Spectrophotometric determination of p-aminophenol alone or in the presence of acetaminophen.

Small amounts of p-aminophenol were analyzed quantitatively by mixing with 4-nitro- or 2,4-dinitrobenzaldehyde in neutral alcoholic solution and then quantitatively forming the respective Schiff bases, 4'-nitro- and 2',4'-dinitrobenzylidene-4-hydroxyaniline, by evaporating the alcoholic solutions to dryness. The Schiff bases thus formed were examined spectrophotometrically. This procedure was also used for the determination of p-aminophenol in the presence of its degradation products. It was necessary, however, to separate the respective Schiff bases by TLC from the degradation products and the reaction mixture prior to spectrophotometric examination. Small amounts of p-aminophenol present in acetaminophen were quantitatively determined by applying the procedure to a water-ethanol (95:5 v/v) extract of the samples of acetaminophen. TLC was used to separate the respective Schiff bases from the reaction mixture and acetaminophen prior to spectrophotometric examination.