Fluorometric measurement of theophylline.

We have developed a simple, sensitive procedure in which theophylline in a solution of cerium(IV) acts as an oxidizable compound to produce fluorescent cerium(III) when combined with a microsolvent for extraction at pH 7.9. This method provides excellent sensitivity and specificity because other xanthines and phenobarbital, secobarbital, amobarbital, and phenytoin do not interfere. Day-to-day reproducibility (coefficient of variation, 6%) is attained for theophylline concentrations of 10 and 20 mg/L. Results correlate well with liquid chromatography and enzyme immunoassay procedures. Total analysis time for a single sample is 10 min.