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ZHU Shuai,SHEN Ya-ting,JIA Jing,LAO Chang-ling.Determination of Organic Selenium Compounds in Crops by Liquid Chromatography-Quadrupole/Electrostatic Field Orbitrap High-resolution Mass Spectrometry[J].Rock and Mineral Analysis,2021,(2):262-272
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Determination of Organic Selenium Compounds in Crops by Liquid Chromatography-Quadrupole/Electrostatic Field Orbitrap High-resolution Mass Spectrometry
Received:May 13, 2020  Revised:September 29, 2020
DOI:10.15898/j.cnki.11-2131/td.202005130070
Key words: organic selenium|crop|quadrupole/obitrap high-resolution mass spectrometry|ultrasonic enzyme extraction
Author NameAffiliation
ZHU Shuai Key Laboratory of Eco-Geochemistry, Ministry of Natural Resources, National Research Center for Geoanalysis, Beijing 100037, China 
SHEN Ya-ting Key Laboratory of Eco-Geochemistry, Ministry of Natural Resources, National Research Center for Geoanalysis, Beijing 100037, China 
JIA Jing Key Laboratory of Eco-Geochemistry, Ministry of Natural Resources, National Research Center for Geoanalysis, Beijing 100037, China 
LAO Chang-ling College of Earth Science, Guilin University of Technology, Guilin 541004, China 
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Abstract:
      BACKGROUND: As more attention is paid to selenium-rich products, the research on the determination of selenium content in crops has become more and more significant. However, existing methods for determining organic selenium has interferences of the matrix effect and polyatomic ion, which affect the accuracy of the measurement.
OBJECTIVES: To establish a rapid method to determine selenium species pf organic selenium in agricultural products by liquid chromatography-quadrupole/electrostatic field orbitrap high-resolution mass spectrometry (LC-Q Exactive Orbitrap MS).
METHODS: The selenium species were extracted using an ultrasonic extraction system with a mixture of protease XIV. The separation was carried out on a Waters Symmetry RP18 column by gradient elution with water and acetonitrile as mobile phases. The selenomethionine, selenocystine and methylselenocysteine were simultaneously analyzed in switching positive and negative modes. The quantitative and qualitative analyses were carried out by high-resolution mass spectrometry with electrospray ionization (ESI) source in negative ion acquisition mode under Full MS/dd-MS2 mode.
RESULTS: Under the optimal conditions, good linearity was obtained in the respective concentration ranges. The limits of detection for three compounds were in the range of 1.0-4.7μg/kg. The recoveries ranged from 76.4% to 116.0% with relative standard deviations less than 6.5%.
CONCLUSIONS: Compared with existing methods, this method has a wider linear range and is suitable for the analysis of a variety of grain and vegetable samples. The established method has been applied to the determination of the edible part of a variety of crops in Heilongjiang, which is the main grain production area in China. The results show that selenomethionine is the main ingredient in cereals, and methylselenocysteine is the main ingredient in vegetables, and that the organic selenium content of crops in this area is at a low level. Therefore, selenium supplementation is urgently needed.