Improved high-performance liquid chromatographic method for the simultaneous determination of caffeine and its N-demethylated metabolites in plasma using solid-phase extraction
Hartley, R.; Smith, I.J.; Cookman, J.R.
Journal of Chromatography 342(1): 105-117
1985
ISSN/ISBN: 0021-9673 PMID: 4044740 DOI: 10.1016/s0378-4347(00)84493-x
Accession: 040380204
An improved high-performance liquid chromatographic method for the simultaneous determination of caffeine and its N-demethylated metabolites in plasma is described. Excellent resolution of all components is provided by reversed-phase chromatography using a mobile phase consisting of 1% acetic acid-methanol (83:17) at a flow-rate of 2.7 ml/min, in conjunction with a Waters Assoc. Nova-Pak C18 column which was protected by a Waters Assoc. Guard-Pak precolumn module containing a Guard-Pak CN cartridge. Rapid extraction of caffeine and the dimethylxanthines from plasma was achieved using reversed-phase octadecylsilane bonded-silica columns (Bond-Elut C18). With only 100 microliters of sample, plasma levels in the region of 50 ng/ml for the dimethylxanthines and 100 ng/ml for caffeine can be determined using ultraviolet detection at 273 nm. The method has been used for measuring umbilical cord plasma samples to provide information regarding foetal exposure to caffeine and its metabolites and is also suitable for therapeutic drug monitoring of caffeine and theophylline levels in the treatment of neonatal apnoea.