Reliable fifteen-minute assay for theophylline

We describe a reliable, rapid high pressure liquid chromatography assay for serum theophylline which can be performed on 0.5 ml or smaller samples. The procedure involves extraction, centrifugation and sampling all in the same disposable centrifuge tube. In the therapeutic range the coefficients of variation for within-day and day-to-day assays are 1.0% and 2.6%, respectively. The sensitivity of the method is better than 1 microgram/ml in serum. The minimum number of steps, rapid elution and use of only peak heights contribute to the reliability and rapidity of the assay.