Combination of LC-ICP-MS, LC-MS and NMR for investigation of the oxidative degradation of selenomethionine.

Selenomethionine (SeMet) was oxidized by heating an acidic solution with hydrogen peroxide. Samples were taken before and during the oxidation process. The oxidation products were separated by cation exchange chromatography followed by ICP-MS detection to identify the selenium containing compounds as well as electrospray ionization MS detection to determine the masses of the degradation products. Furthermore, the samples were analyzed by (77)Se-NMR. The first appearing degradation product was selenomethionine selenoxide, which was converted via the deaminated selenoxide to methane seleninic acid and selenite.