Integration of biochemical separation and inductively coupled plasma mass spectrometry measurement for selenium species in tea samples

Selenium is a crucial trace element for antioxidant defense and immune function, with its health benefits varying significantly based on its chemical form. Tea, a widely consumed beverage, holds potential as a significant dietary source of selenium. However, the variations in selenium content and speciation in tea, influenced by cultivation and processing methods, have not been thoroughly studied, nor has the effect of brewing conditions on selenium release. This work addresses these gaps by developing a method utilizing inductively coupled plasma mass spectrometry to accurately quantify total selenium content and its speciation in tea samples. We optimized microwave digestion conditions to establish a rapid and efficient protocol for measuring total selenium and evaluated different brewing conditions to determine their impact on selenium extraction, identifying optimal parameters to maximize selenium intake from tea infusions. Additionally, AG1 x 4 ion exchange resin was employed to separate inorganic from organic selenium, and a method to extract and purify selenium bound to key tea components such as polyphenols, polysaccharides, and proteins was developed, with the extraction parameters optimized. Our findings provide a thorough understanding of selenium speciation in tea and highlight the importance of brewing conditions in enhancing selenium bioavailability, offering valuable insights for the development of selenium-enriched teas and advancing healthier dietary practices.