Poster Presentation Australian Society for Medical Research Annual Scientific Meeting 2016

Dietary pre-workout supplements usually contain caffeine and other botanical extracts to promote weight-loss and to improve athletic performance [1]. The increase in popularity of these products [2] and reports of adverse effects [3] drives the need to investigate the amount of caffeine and its dimethylxanthine derivatives present. A rapid, sensitive and simple HPLC-UV/MS method was developed for the simultaneous quantitation and detection of caffeine, theobromine, paraxanthine, and theophylline in domestic and overseas pre-workout supplements. Five supplements were prepared and extracted using solid phase extraction. The chromatography involved a gradient elution (A: water and B: acetonitrile, adjusted to pH 4.5 with 0.1% formic acid) on a CSH phenyl-hexyl column, detected with a UV/Vis-detector (272nm) coupled with mass confirmation on a single quadrupole (QDa) mass detector in positive electrospray ionisation (ESI) scan mode. Calibrations were linear with determination coefficients of r²> 0.999, except for theobromine (r²=0.991). The supplement with the highest concentration of caffeine (210 mg/serve) did not state the presence of caffeine on its label. Furthermore, a supplement stating to contain 100mg/serve of caffeine was found to contain 188mg/serve (Figure 1). The intermediate precisions (RSD, %) were less than 10.5%, with overall recoveries (RSD, %) between 81.5-89.5%. This method offers a reliable and fast analysis that is also applicable to biological fluids analysis as it boasts the separation of theophylline and paraxanthine with good resolution.

Table 1: Amount of caffeine reported compared to respective label contents after back-calcuations. Equivalent caffeine content in 1 cup of coffee= 100mg