Determination of the urinary metabolites of caffeine and theophylline by high-performance liquid chromatography. A comparative study of a direct injection and an ion-pair extraction procedure.
Chromatographic separation of methylxanthine metabolites was achieved using a Hypersil octadecylsilane column with a simple concave gradient elution programme of 0-12.75% acetonitrile in 1% tetrahydrofuran, pH 4.8, and the eluted components were detected by monitoring their absorption at 280 nm. An extraction procedure involving the formation of an ion-pair complex was developed which gave significant improvements over previously described methods including a shorter chromatographic run of 20 min. A thorough comparison of this procedure with a more convenient alternative involving direct injection of diluted urine specimens showed that the latter analysis was adequate for the quantitation of the major urinary metabolites of caffeine and theophylline.
N R
NR
Scott
J
J
Chakraborty
V
V
Marks
D002110:Caffeine / Q000652:urine*; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D006801:Humans; D013806:Theophylline / Q000652:urine*
D002110:Caffeine; D013806:Theophylline