Abstract: An effective method was developed for the speciation analysis of selenium in digests of Se-enriched Cordyceps militaris and selenium-enriched yeast prepared using in vitro biomimetic gastrointestinal tract models by microwave digestion-high resolution-continuum source graphite furnace atomic absorption spectrophotometry (HR-CS GFAAS). The aim was to study the influences of gastric and intestinal digestion on the speciation and bioavailability of Se in selenium-enriched food. The gastric and intestinal digests were separated through a 0.45 μm membrane filter into suspended and soluble Se, and inorganic and organic Se from the soluble fraction were further separated using D101 macroporous resin. Moreover, Se-binding protein and polysaccharide were precipitated by acetone and ethanol, respectively. The partition behaviors of Se from Se-enriched food in the stomach and gut were simulated with n-octyl alcohol and monolayer liposome as cell membrane, respectively. The optimal analysis wavelength for Se was 196.026 7 nm. A mixture of 1 g/L Pd(NO3)2 and 0.5 g/L Mg(NO3)2 (5 μL) was selected as the best matrix modifier, and an ashing temperature of 1 100 ℃ and an atomization temperature of 2 200 ℃ were used. The results showed that Se contents in selenium-enriched Cordyceps militaris and selenium-enriched yeast were determined to be 2.129 and 27.75 μg/g, respectively under these conditions. The contents of all Se forms except suspended Se in the intestinal digest were higher than in the gastric digest. n-Octyl alcohol-soluble Se and monolayer liposome-bound Se were more abundant than water-soluble Se during simulated intestinal digestion.

Key words: in vitro biomimetic gastrointestinal tract models, selenium-enriched, speciation analysis, bioavailability assessment, high resolution-continuum source graphite furnace atomic absorption spectrophotometry (HR-CS GFAAS)