Selenium speciation studies in Se-enriched chives ( Allium schoenoprasum) by HPLC-ICP–MS

Abstract

In this study, three liquid chromatographic techniques were employed to better understand selenium species distribution in Chives ( Allium schoenoprasum) separately grown in three different supplementation media Se(IV), Se(VI), and SeMet. The highest selenium accumulation up to 700 μg Se g −1 was observed in the case of the Se(VI)-enriched samples on the basis of total selenium measurements. Size-exclusion chromatography (SEC-HPLC) was performed for investigation of selenium containing proteins in chives. For speciation of selenium containing amino acids, reversed-phase ion-pairing chromatography (RP-IP-HPLC) and for enantiomeric separations, a crown ether column was used. In all three cases online detection with inductively coupled plasma mass spectrometry was performed for selenium specific detection. Two extractions (perchloric acid–ethanol and enzymatic) were carried out on chive samples. Speciation analysis on the chives grown in three different media revealed that selenium distribution among different forms of amino acids in the sample strongly depends on the type of enrichment employed. Enrichment with Se(VI) leads to accumulation of selenium in inorganic forms, while in case of Se(IV) and SeMet-enriched samples, methyl-selenocysteine and selenocystine were found to be present. Not surprisingly, chiral speciation revealed the presence of the l-enantiomeric forms of selenoamino acids in the sample. The major enantiomer found in the perchloric acid–ethanol extracts was l-MeSeCys, while in the enzymatic extracts l-SeMet was also detected.