On-line determination of selenium compounds in tea infusion by extractive electrospray ionization mass spectrometry combined with a heating reaction device

Abstract

Selenium is one of the important trace elements in the human body. Its deficiency will directly affect human health. With people's attention to health, the content of selenium in food has gradually attracted attention. However, detecting selenium compounds in complex samples remains a challenge. In this work, we built an online heating-reaction device. This device combines the electrospray extraction ionization mass spectrometry (EESI-MS) with the heating reaction device, which can simultaneously detect various selenium compounds in complex liquid samples. Under acidic conditions, the sample was heated and catalyzed by a heating reaction device, so that the SeO32− and O-phenylenediamine (OPD) could generate 1,3-dihydro-2,1,3-benzoselenadiazole. Based on the above reactions, we can detect organic selenium, inorganic selenium and other compounds in liquid samples by organic mass spectrometry. In this experiment, we determined the content of three forms of selenium: selenomethionine (SeMet), L-selenocystine (SeCys(2)), and sodium selenite. The calibration curves for SeMet, SeCys(2), and sodium selenite showed strong linearity within a range of 0.50-50.00 μg/L. The limits of detection (LOD) for the three compounds were 0.22 μg/L, 0.27 μg/L, and 0.41 μg/L, respectively. The limits of quantification (LOQ) were 0.68 μg/L, 0.81 μg/L, and 1.23 μg/L, respectively. Spiked recoveries at three levels ranged from 98.8% to 106.1%. In addition, this method can simultaneously detect three selenium compounds and three other specific chemical components in tea infusion samples, providing a rapid and efficient method for identifying tea quality.