Speciation of D,L-selenomethionine enantiomers on a β-cyclodextrin column with fluorimetric and on-line hydride generation inductively coupled plasma mass spectrometric detection

Abstract

O-Phthalaldehyde (OPA) and 2,3-naphthalenedicarbox-aldehyde (NDA) were investigated as pre-column derivatizating reagents in order to achieve the chiral separation of D,L-selenomethionine enantiomers on a β-cyclodextrin column using fluorimetric detection. Good resolution was achieved between the NDA-derivatized enantiomers with a mobile phase of 60% v/v methanol–0.5% triethylammonium acetate (pH 5). The sensitivity and selectivity of the fluorimetric detection of the derivatives were compared with selenium-specific detection by on-line microwave-HG-ICP-MS. Limits of detection of 2.7 and 70 µg l–1, respectively, were obtained. This sensitivity allowed the detection of small amounts (0.1–1%) of D-selenomethionine in commercially pure L-selenomethionine samples using both detectors. The HG-ICP-MS detector proved to be superior in terms of selectivity to selenium, as demonstrated by preliminary results obtained for D,L-selenomethionine determination in complex samples (selenium-enriched yeast). Selenomethionine could not be determined in such samples by fluorimetric detection owing to the presence of many other interfering amino acids at concentrations higher than that of selenomethionine which react with OPA and NDA.