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. 2019 Nov 3:2019:2926580.
doi: 10.1155/2019/2926580. eCollection 2019.

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

Ahmad Aqel  1 , Ahmed Almulla  1 , Asma'a Al-Rifai  2 , Saikh M Wabaidur  1 , Zeid A ALOthman  1 , Ahmed-Yacine Badjah-Hadj-Ahmed  1
Affiliations

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

Ahmad Aqel et al. Int J Anal Chem. .

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.

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Conflict of interest statement

The authors declare that they have no conflicts of interest.

Figures

Figure 1
Figure 1
Chemical structures and chromatogram of the 1.0 μg/mL theobromine, theophylline, and caffeine mixed standard solution at the optimized conditions.
Figure 2
Figure 2
Representative UHPLC-MS chromatograms for some of the studied tea samples: (1) theobromine, (2) theophylline, and (3) caffeine.
See this image and copyright information in PMC

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