Separation and determination of Se-compounds by liquid chromatography coupled with electrospray mass spectrometry

A method for Selenocystine and Selenomethionine determination by LC-ES-MS was developed in this work. The mass spectrometer was used in a positive mode and the m/z used for the identification of Selenomethionine and Selenocystine were 198.35 and 337.15, respectively. The selenium species were separated using a LC system. A silica chromatographic column (ZORBAX Eclipse XDB-C(8) of 50 mm length and 2.1 mm internal diameter (particle size 3.5 microm)) was used. The separation was realised in isocratic mode, using methanol:water (1:1) with 1% of acetic acid and a flow rate of 200 microL min(-1). The developed method was precise (RSD of 4.5% and 3.9% for Selenomethionine and Selenocystine, respectively) and sensible (limit of detection (LOD) 0.06 and 0.99 mg L(-1) for selenomethionine and selenocystine, respectively).