Simultaneous microdetermination of theophylline, caffeine and phenobarbital in blood collected on paper

Abstract A sensitive and selective gas chromatographic method has been developed for the simultaneous determination of theophylline, caffeine and phenobarbital. Blood collection is performed by dropping 30 μl of blood onto a disc of a special paper. Vinbarbital is used for quantitation by the internal standard method. The chromatographic separation is performed on a 3% OV-17 column, after pentylation of the methylxanthine and internal standard, and the compounds are detected with a nitrogen-sensitive detector. The sensitivity of the method allows the monitoring of theophylline therapy in premature newborns by the differential determination of caffeine and theophylline. The sampling method does not affect the accuracy and precision and is very suitable for the collection of small blood samples.