Liquid-chromatographic analysis for serum theophylline in less than 70 seconds

We describe a sensitive, specific, and very fast liquid-chromatographic assay for serum theophylline, involving a commercially available high-speed reversed-phase column and a micro-flow-cell-equipped detector. Each analysis requires only 100 microL of serum (as little as 25 microL may be used when necessary), and chromatography is complete in less than 70 s. Analytical recovery of theophylline added to serum ranged from 97 to 102%. Between-run precision (CV) ranged from 2.1 to 3.5%. The lower limit of detection for theophylline is 0.5 mg/L, and linearity extends to 50 mg/L. Numerous drugs and xanthine metabolites tested do not interfere.