Spectrophotometric Determination of Caffeine in Soft drinks available in Libyan local markets

Abstract

In this study, caffeine contents in soft drinks samples were determined photometrically using UV/Visible spectrometry which is a rapid, precise and accurate method. Calibration solutions were prepared in the concentration range of (1-40 ppm ) from a 100 ppm stock solution, and (0.25 ppm and 0.5 ppm) were prepared from 10 ppm standard solution. Absorbance of all calibration solutions was measured at the absorption maximum at 275 nm. Caffeine was extracted from soft drinks samples by hydrochloric acid due to the difficulty of solubility of caffeine in water due to its organic composition. The estimate was made using hydrochloric acid as a reference. The concentration of unknown samples was read from the calibration graph. Various concentrations of caffeine were present in samples of soft drinks, results showed that in case of samples the highest amount of caffeine (892.448mg/L) was present in Schweppes and the lowest amount (11.163mg/L) in Sprite. The levels of caffeine in eleven samples are well below the maximum allowable limits set by the food regulatory bodies whereas, four brands of soft drinks contained high level of caffeine, consequently, they are harmful for health.