Certification of caffeine reference material purity by ultraviolet/visible spectrophotometry and high-performance liquid chromatography with diode-array detection as two independent analytical methods

Caffeine reference material certified for purity is produced worldwide, but no research work on the details of the certification process has been published in the literature. In this paper, we report the scientific details of the preparation and certification of pure caffeine reference materials. Caffeine was prepared by extraction from roasted and ground coffee by dichloromethane after heating in deionized water mixed with magnesium oxide. The extract was purified, dried, and bottled in dark glass vials. Stratified random selection was applied to select a number of vials for homogeneity and stability studies, which revealed that the prepared reference material is homogeneous and sufficiently stable. Quantification of caffeine purity % was carried out using a calibrated UV/visible spectrophotometer and a calibrated high-performance liquid chromatography with diode-array detection method. The results obtained from both methods were combined to drive the certified value and its associated uncertainty. The certified value of the reference material purity was found to be 99.86% and its associated uncertainty was ±0.65%, which makes the candidate reference material a very useful calibrant in food and drug chemical analysis.

Scientific details of the certification process of pure caffeine reference material (RM) have been reported for the first time in this paper. Caffeine was extracted from coffee, purified, and then bottled. The homogeneity study revealed that the RM was homogenous and stable. Certification of the caffeine RM purity % was done by high-performance liquid chromatography with photodiode array detection (HPLC-DAD) and UV/visible spectrophotometry as two independent analytical methods. The certified value was found to be 99.86 ± 0.65 %, which indicates that this prepared certified RM (CRM) is a good calibrant in food and drug analysis.146