An efficient and low-cost method for the determination of selenium in selenium-enriched tea by high-performance liquid chromatography coupled with 3,3′-Diaminobenzidine derivatization

In this study, a novel analytical method was developed and validated for the quantification of selenium in selenium-enriched tea. The various valence states of selenium present in tea were converted to Se(IV) through oxidation and reduction reactions. To chemically react with Se(IV), 3,3′-Diaminobenzidine (DAB) was employed to produce Se-DAB derivatives. These derivatives were then analyzed and quantified using high-performance liquid chromatography (HPLC) with a NH2 column specifically designed for the target compound. The peak area of Se-DAB exhibited excellent linearity within the concentration range of 0.01–50 μgmL−1 (R2 = 0.9999). The method demonstrated a limit of detection (LOD) of 0.01 mgkg−1 and a limit of quantification (LOQ) of 0.03 mgkg−1. Moreover, the recoveries of Se-DAB spiked at different concentrations ranged from 81.2 % to 96.7 %, with relative deviations (RSDs) of 0.72 %–4.23 % (n = 6). Additionally, the RSDs under different batches varied from 3.42 % to 8.57 % (n = 9). The method exhibits good stability and repeatability. The results obtained by applying the method to 24 samples of selenium-rich tea show high consistency with the AFS method. The difference range between the two methods is 0.017–0.027 mg/kg, with an average difference of 0.005 mg/kg. Furthermore, this method offers the advantage of flexibility in analyzing large quantities of green tea samples, while utilizing lower instrument and reagent costs. Therefore, it can be considered as a new and cost-effective method for detecting selenium content in selenium-rich tea.