Separation and spectrophotometric determination of theophylline and hydroxyethyltheophylline in a pharmaceutical syrup

A simple chromatographic procedure was developed for the separation and determination of theophylline and hydroxyethyltheophylline. An aliquot of diluted syrup was pipetted into a chromatographic column containing a strong anion-exchange resin, which retains theophylline and allows the hydroxyethyl derivative to pass through it. Theophylline was subsequently eluted with 1 N HCl and determined by difference spectrophotometry at 284 nm; its derivative was determined at 272 nm.