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

Quantification of theobromine and caffeine in saliva, plasma and urine via liquid chromatography–tandem mass spectrometry: A single analytical protocol applicable to cocoa intervention studies

“…Several techniques for protein removal and biological sample clean-up have been reported for theobromine and caffeine quantitation, with LLE [10,[15][16][17][18][19][20][21][22][23][24]42] and SPE [25][26][27][28][29][30] being the most widely used. Co-extraction of interfering species and incomplete analyte isolation due to the varying heterogeneity of the metabolite class [16] may occur with these techniques.…”

“…Although these procedures isolate and enhance the response of the target analyte, they are often time consuming, difficult to automate, reduce precision and incur sample loss. Several different pre-analytical protocols have been employed to minimize the deleterious effects of complex biofluid matrices, with liquid-liquid extraction (LLE) [15][16][17][18][19][20][21][22][23][24] and solid-phase extraction (SPE) [25][26][27][28][29][30] being the most common for these analytes. Once isolated from the matrix, numerous analytical techniques have been used for multiplex methylxanthine analyses including radioimmunoassay (RIA) [31], thin-layer chromatography (TLC) [26], capillary gas chromatography (GC) [32] and micellar electrokinetic electrophoresis (MEKC) [33,34].…”

Caffeine as a metabolic probe: NAT2 phenotyping

“…Preliminary studies had indicated that the MRs were independent of the dose of caffeine ingested provided subjects adhered to the 2 h xanthine fast. All urine was stored at -20" C prior to analysis of caffeine metabolites using the method of Dobrocky et al [18].…”

An in vitro technique for the rapid determination of drug entry into breast milk.

“…The tube was capped and shaken horizontally in an incubator for defined intervals of up to 4 h at 370 C, when milk and plasma were analysed for drug content either by h.p.l.c. (caffeine [5], warfarin [6]) or scintillation counting (all other drugs). Table 1 lists the drugs studied.…”