Rapid method for the routine determination of caffeine and its metabolites by high-performance liquid chromatography.

Caffeine is a popular compound for phenotyping individuals for CYP4501A2, xanthine oxidase (XO) and N-acetyltransferase (NAT) utilising urinary metabolites. The analysis is complex since at least thirteen metabolites are excreted by man. Past methods have been less than satisfactory in that either not all the metabolites have been resolved and/or extractions selective for particular groups of metabolites are required prior to chromatography. We report a method for the rapid analysis of caffeine and metabolites in urine that negates the requirement for an extraction step, and also a method for plasma analysis.