Abstract

The chiral speciation of DL-selenomethionine by capillary electrophoresis (CE) with UV absorbance and inductively coupled plasma mass spectrometry (ICP-MS) is described. Chiral derivatization of DL-selenomethionine with 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide (Marfey's reagent) forms diastereomers that are separated with CE in reversed polarity. Three CE buffer systems were evaluated using UV absorbance detection. A 30 mM ammonium phosphate buffer at pH 3.3 was chosen for good resolution of the D- and L-forms in under 14 min. Limits of detection for D- and L-selenomethionine were 250 ppb (ng mL⁻¹) using CE-UV, and 50 ppb using CE-ICP-MS. The migration time reproducibility of both detection limits was comparable (∼2%). This method was applied to the qualitative chiral identification of selenomethionine in selenized yeast digested with proteinase K (enzymatic hydrolysis).