Comparison of three digestion methods for determination of selenium in green tea samples using fluorescence spectrometry

Abstract

Abstract Various digestions are available for the determination of selenium (Se) in environmental samples. This study aimed to investigate the most effective digestion method for the determination of Se in green tea samples that effective, eco-friendly, and low cost. Samples were digested with three different acid compositions, the aqua regia method (a mixture of nitric acid-hydrochloric acids HNO3-HCl) in a ratio 1:3, only nitric acid HNO3, and reverse aqua regia method (a mixture of nitric acid-hydrochloric acids HNO3-HCl) in a ratio 3:1. Analysis of Se was conducted using fluorescence spectrometry after derivation by 2,3-diamino naphthalene (DAN). The results show that the aqua regia method was the highest fluorescence intensity. It had given a significant fluorescence intensity of 9.0510 a.u. for 2 mL sample, 26.3689 a.u. for 5 mL sample, 54.4308 a.u. for 10 mL sample, respectively. In addition, the aqua regia digestion resulted in the selenium form in the sample has been converted to tetravalent selenium, and there was a silicone compound as precipitation can be found after digestion. The aqua regia method provides a highly effective digestion method for selenium in green tea samples under fluorescence spectroscopic investigation.