Determination of 5 Selenium Species in Seafood Products by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

0.2 g (accurate to 0.000 1 g) of the prepared freeze-dried seafood product sample was hydrolyzed with 30 mg papain (800 U·mg^-1) in an aqueous solution system with pH 8.0 at 50℃ for 12 h with the speed of 180 r·min^-1. After vortex for 3 min and centrifugation for 10 min, the obtained supernatant was passed through 0.22 μm filter membrane, and 5 selenium species in the filtrate could be separated in 11 min, using Agilent ZORBAX SB-AQ column (250 mm×4.6 mm, 5 μm) as the stationary phase and 10 mmol·L^-1 citric acid solution (pH 4.75) as the mobile phase for isocratic elution at 0.6 mL·min^-1. Then selenate (Se⁶⁺), selenite (Se⁴⁺), L-Se-methylselenocysteine (Me-Se-Cys), selenomethionine (Se-Met) and selenoethionine (Se-Et) in seafood product sample solution were determined by inductively coupled plasma mass spectrometry. As shown by the results, the same linear ranges of the standard curves of 5 selenium species were found within 500 μg·L^-1, with detection limits (3S/N) in the range of 1.231-2.423 μg·L^-1. Tests for recovery were made on seafood product samples at three concentration levels by standard addition method, giving results in the range of 81.3%-118%, with intra-day RSDs (n=6) and inter-day RSDs (n=6) of the determined values less than 9.0%. This method was applied for the analysis of commercial seafood product sample, and it was shown that the determination results of selenomethionine in small yellow croaker and hairtail were higher than those of Atlantic salmon and Atlantic cod reported in the literature, indicating that eating small yellow croaker and hairtail in China could provide a higher level of selenomethionine for people. In addition, squilla was also an important source of selenomethionine supplement.