Comparison of Derivative Spectrophotometry and Partial Least Square (PLS-1) Calibration for the Determination of Caffeine in Energy Drinks

Abstract

Caffeine, a xanthine alkaloid, occurs in teaplants, coffee, mate leaves and cola nuts. It is also commonly found beverages, such as cola drinks, tea and energy drinks. In this work, two methods for the determination of caffeine in energy drinks by derivative spectrophotometry and by partial least-squares multivariate spectrophotometric calibration (PLS-1) are described. Proposed methods involve background correction methods that interferences from vitamins, taurin and food colours were minimized by treating the sample with basic lead acetate and NaHCO3 for the analysis of caffeine in energy drinks. In the first method, derivative spectrophotometry, the amplitudes in the first derivative spectra at 287 and 260 nm were selected to determine caffeine. The concentration range of application is 3-15 mu g mL(-1) for caffeine. In the other method, PLS-1, the absorption spectra of caffeine solutions were recorded between 240-320 nm and the absorbance values recorded every 5 nm. The methods were applied to determine caffeine in commercial energy drinks and the results obtained are compared. It was found that these methods don't require expensive solvents and can confidently be used for rapid, precise and sensitive quantitation of caffeine in energy drinks, especially for routine quality control analyses.