Determination of Selenium Species in Milk Powder by IC-ICP-MS

IC combined with ICP-MS was applied to the determination of selenium species in milk powder. The milk powder sample was precipitated with acetic acid and extracted with mobile phase. The Hamilton PRP X-100 anion column (250 mm×4.6 mm, 5 μm) along with 5 mmol·L-1 citric acid, 10 mmol·L-1 ammonium acetate and 0.1% (φ) trifluoro acetic acid as mobile phase (pH 5.2) was used for separation. The 4 selenium species, i.e. selenate ［Se(Ⅵ)］, selenite ［Se(Ⅳ)］, selenomethionine (SeMet) and selenocystine ［(SeCys)2］ were completely separated within 8 min. The detection limits of the method found ranged from 0.03, 0.10 μg·L-1. Recovery rates measured by standard addition method were in the range of 25.0%-105%, with RSD (n=6) in the range of 1.8%-7.8%.