SIMULTANEOUS DETERMINATION OF CAFFEINE, THEOBROMINE, THEOPHYLLINE IN TEA USING ULTRAVIOLET - VISIBLE SPECTROSCOPY COMBINED WITH MULTIVARIATE ANALYSIS

Abstract

   An analytical procedure based on the use of ultraviolet – visible spectroscopy combined with multivarite regression was applied for simultaneous determination of caffeine, theobromine and theophylline in 53 Vietnamese tea samples. The 240-310nm spectral window was used for data acquisition.The partial least squares (PLS) and Artificical Neural Network (ANN) method were used to calculate concentration of 3 ananlytes in samples.  The same model of PLS and ANN with standard matrix of 44 tea samples (the contents of 3 analytes were determined by high performance liquid chromatography) were applied for individual and/or simultaneous determination of caffeine, theobromine and theophylline in samples. A matrix of test samples including 9 tea samples was used to assess the accuracy of the models. Compared with PLS, the ANN model was better with lower realtive error. This work demonstrated that ultraviolet – visible spectrophotometry with ANN model could be simply used to analyse xanthine’s contents in tea with simple sample preparation.

Keywords: caffeine, theobromine, theophylline, multivariable calibration, tea, ultraviolet – visible spectrophotometry