Rapid and Sensitive Determination of Methylxanthines in Commercial Brands of Tea Using Ultra-High-Performance Liquid Chromatography-Mass Spectrometry

Abstract

Recently, chromatographic techniques have the potential to be greener in order to reduce the environmental impact. In this work, a new simple, sensitive, efficient, and green analytical method based on UHPLC-MS has been developed for a quick determination of methylxanthines including caffeine, theobromine, and theophylline in tea. Under the optimum conditions, a baseline separation has been achieved within 30 seconds, using isocratic elution consisting of 90% water and only 10% acetonitrile at 0.5 mL/min flow rate (3 mL acetonitrile per hour). The mass spectrometer was operated with the SIR mode in ESI+. The developed method was found to be linear in the range of 0.03–5 μg/mL, with correlation coefficients greater than 0.9995 for the three compounds. The respective values of LOD were found to be 0.025, 0.015, and 0.01 μg/mL for caffeine, theobromine, and theophylline, respectively. The proposed assay was applied to 30 commercial tea samples of different brands. Both caffeine and theobromine were found in all tea samples with maximum concentration in sample no. 15, corresponding to 32.6 and 2.72 mg/g of caffeine and theobromine, respectively. On the contrary, theophylline was not detected at all in most samples. When compared with all previous studies that dealt with the same compounds in different matrices, the developed method was found to be the fastest, allowing high-throughput analyses with more than 100 samples/h. The results prove that the method is suitable for routine analysis of methylxanthines and to distinguish the quality of tea samples of various brands.

Ultra-High Adsorption Capacity of Core–Shell-Derived Magnetic Zeolite Imidazolate Framework-67 as Adsorbent for Selective Extraction of Theophylline

“…The data are shown in Table 1 and Figure S5 . The TP content of jasmine tea, black tea, and green tea are 5.80, 4.31, and 1.53 μg/g, respectively, but oolong tea and rabbit plasma are not detected, which is consistent with the previous reports [ 2 , 3 ]. Furthermore, high levels of theobromine and caffeine that are hundreds and thousands of times higher than TP are found in the four tea samples.…”

“…Theophylline (1,3-dimethyl-7 H -purine-2,6-dione) (TP) is a dimethylxanthine derived from the xanthine purine base of alkaloid, which occurs naturally in most kinds of teas (jasmine tea, black tea, oolong tea, etc.) and cocoa beans in trace amounts [ 1 , 2 , 3 ]. TP is an important bioactive component of tea, which has various bioactivities at low doses [ 4 ].…”

“…High-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) has been employed to determine TP from various tea and biological samples [ 3 ]. However, the direct determination of TP in tea and biological samples is always faced with complicated matrix interferences and trace analytes.…”

Green coffee polyphenols in formulations of functional yoghurt and their quality attributes

“…Likewise, alkaloid estimation was conducted as per the method stated by Aqel et al . (2019) using an isocratic programme. Compounds were identified and quantified by retention time and the linear calibration curves of standard compounds.…”

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“…While caffeine is one of the main components in coffee, several derivatives of caffeine, such as xanthin, have also been reported 31 . Furthermore, different amounts of caffeine compounds have been reported in green and roasted beans for both Arabica and Robusta coffee 32 . Therefore, the literature studies have indicated caffeine's antimicrobial activity as the primary compound and its minor composition.…”