A Micro Method for the Ultraviolet Spectrophotometric Determination of Theophylline1

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Abstract
An ultraviolet spectrophotometric method for the analysis of serum theophylline has been developed for use with samples from pediatric and neonatal populations (1). The method a) avoids interference from caffeine, salicylates, and barbiturates; b) gives excellent recoveries; and c) can be performed with 50 µl of serum. Theophylline in serum is extracted with a chloroform-isopropanol solvent and then back-extracted into dilute sodium hydroxide. The pH is adjusted to 9 with ammonium chloride. Linear curves are observed for theophylline-fortified serum from 5 to 100 mg per liter and recoveries of 87 to 104% were found for the same range of concentrations.