Identification and characterization of selenium species in enriched green onions (Allium fistulosum) by HPLC-ICP-MS and ESI-ITMS

MONICA SHAH,; S KANNKUMARAT, SASI; WUILLOUD, JCA O ALTAMIRANO, JC; G. WUILLOUD, RODOLFO; A CARUSO, JOSEPH

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY

Royal Society of Chemistry

Lugar: London; Año: 2004 vol. 19 p. 381 - 386

0267-9477

In this study speciation of selenium in selenium-enriched green onions (Allium fistulosum) was done with reversed-phase ion-pairing high performance liquid chromatography (RP-IP-HPLC) and size-exclusion chromatography (SEC) coupled on-line to ICP-MS for selenium specific detection. The plant extract obtained using sodium hydroxide (0.1 mol l21) analyzed by SEC (CAPS 10 mmol l21, pH 10.0) with ICP-MS detection showed the incorporation of selenium in both high (y12 kDa) and low molecular weight (0.36–2 kDa) fractions. Presumably protein bound selenoamino acids were released using enzymes (Proteinase K and Protease XIV) and selenoamino acids found in cytosol in their free form were extracted using 0.1 M HCl. Theextracts were analyzed for speciation studies by RP-IP-HPLC [0.1% (v/v) heptafluorobutyric acid, 5% (v/v) methanol, pH 2.5]. Matching the chromatographic retention times with commercially available standards provided evidence for the presence of Se-cystine, methylselenocysteine, Se-methionine, and inorganic selenium. Electrospray ionization ion trap mass spectrometry (ESI-ITMS) confirmed the presence of c-glutamyl-Semethylselenocysteinein green onions as has been reported in other onion types.