Investigation of free and conjugated seleno-amino acids in wheat bran by hydrophilic interaction liquid chromatography with tandem mass spectrometry.

An analytical method for determining seleno-methionine, methyl-seleno-cysteine, and seleno-cystine in wheat bran was developed and validated. Four different extraction procedures were evaluated to simultaneously extract endogenous free and conjugated seleno-amino acids in wheat bran in order to select the best extraction protocol in terms of seleno amino acid quantitation. The extracted samples were subjected to a clean-up by a reversed phase/strong cation exchange solid-phase extraction and analyzed by chiral hydrophilic interaction liquid chromatography-tandem mass spectrometry. The optimized extraction protocol was employed to validate the methodology. Process efficiency ranged from 58 to 112% and trueness from 73 to 98%. Limit of detection and limit of quantification were lower than 1 ng/g. Four wheat bran samples were analyzed for both total Se and single seleno-amino acids determination. The results showed that Se- seleno-methyl-lselenocysteine was the major seleno-amino acid in wheat bran while seleno-methionine and seleno-cysteine were both minor species.