Simultaneous Determination of Caffeine, Theobromine, and Theophylline in Tea by Differential Pulse Adsorptive Stripping Voltammetry Combined with Chemometrics

Nguyen, Thuong Thi Kim; Pham, Tuan Annh; Luu, Thu Huyen; Le, Thi Huong Giang; Do, Huy Hoang; Dang, Minh Huong Giang; Ta, Thi Thao

doi:10.22034/abec.2024.719407

Simultaneous Determination of Caffeine, Theobromine, and Theophylline in Tea by Differential Pulse Adsorptive Stripping Voltammetry Combined with Chemometrics

Document Type : Original Article

Authors

Thuong Thi Kim Nguyen

Tuan Annh Pham

Thu Huyen Luu

Thi Huong Giang Le

Huy Hoang Do

Minh Huong Giang Dang

Thi Thao Ta

Department of Analytical Chemistry, Faculty of Chemistry, University of Science, Vietnam National University, Hanoi, Vietnam

10.22034/abec.2024.719407

Abstract

Adsorptive stripping voltammetry (AdSV) using a glassy carbon electrode combined with chemometrics was investigated for simultaneous determination of caffeine, theobromine, and theophylline in tea samples, offering high selectivity, sensitivity, simplicity, and cost-effectiveness. The optimal electrochemical conditions were 0.01 mol.L^-1 H₂SO₄, an adsorption potential of 0.6V vs. Ag/AgCl/KCl, a scan rate of 0.025 V/s, and an adsorption time of 60 s. Linear calibration graphs for each compound were obtained in the concentration ranges from 1.0×10^-6 to 4.0×10^-5 mol.L^-1, 1.0×10^-6 to 3.0×10^-5 mol.L^-1, and 1.0×10^-6 to 1.4×10^-5 mol.
L^-1 for caffeine, theobromine, theophylline, respectively. In this study, a pre-separation step was not required despite the overlapping voltammetric peaks of caffeine, theobromine, and theophylline in the mixtures, as chemometrics techniques, such as partial least squares (PLS), principal component regression (PCR), and classical least squares (CLS) were applied. Among the three multivariate linear regressions, the PLS method was chosen because it has the smallest relative error, all less than ±11.1%. In contrast, the CLS performed poorly with relative reaching up to ±83%. The proposed novel method was applied to simultaneously determine caffeine, theobromine and theophylline in tea samples. The results showed no significant differences compared to those obtained using high-performance liquid chromatography (HPLC).

Keywords

Adsorptive stripping voltammetry

Chemometrics

Caffeine

Theobromine

Theophylline

Tea samples

Subjects