Abstract
► Validation of a simple and rapid method for caffeine determination in food. ► Caffeine determination on monolithic column is faster, cheaper and more sensitive. ► Greater temperature influence on caffeine extraction from tea than coffee and cocoa. ► Capillary monolithic columns are simple to prepare and fritless with a higher permeability.
Caffeine beverages are widely consumed in the world, so new analytical techniques providing fast and reliable data are essential for a rapid and accurate evaluation of food quality. A capillary hexyl methacrylate monolithic column was designed and prepared for simple, rapid, economical and sensitive high performance liquid chromatography method for the determination of caffeine in food, using a water/acetonitrile (90:10, v/v) mobile phase with ultraviolet (UV) detection. The method was validated over the range 0.16–250μg/mL of caffeine concentration and found to be linear (r>0.995, n=5) with relative standard deviation (RSD) less than 4.0%.
Calibration curves prepared for tea, coffee and cocoa extracts were linear. The limits of detection and quantification were 0.05 and 0.16μg/mL, respectively. Recoveries of caffeine in food samples were found to be ranged from 89.0% to 116.6%, showing a good reliability of this method. Ruggedness and the case of external calibration versus standard addition for the analysis of real samples were also examined. The effect of temperature on the extraction was also investigated. This validated method was compared with the most commonly used conventional octadecylsilica packed column (C18), in terms of analysis time, reagents and solvents consumption, detection and linearity limits, porosity and permeability of each column.