Determination of Acetylsalicylic Acid, Salicylamide, Acetaminophen, and Caffeine in Tablets or Powders by Independent Methods

A method, suitable for automation, has been developed for the determination of four compounds commonly found in analgesic tablets. The tablet is dissolved in 85 percent methanol, filtered to remove the insoluble excipients, and three portions are taken. The first portion is analyzed for aspirin (ASA) by titration; the second portion, for acetaminophen (APAP) and salicylamide (SAL) by UV differential spectrophotometry; and the third portion for caffeine (CAF), either by a unique differential spectrophotometric operation, or by an extraction method, where the caffeine content is determined spectrophotometrically in the UV range. The average relative errors for each of the components are: 0.22% for aspirin, 0.51% for salicylamide, 0.80% for acetaminophen, 2.02% for caffeine by method I, and 1.18% for caffeine by method II.