Abstract: A dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS) method was proposed for the determination of trace selenium in agricultural products digested in closed vessel microwave with nitric acid. Application of methane as the reactive cell gas in the DRC reduced the argon dimer interferences at selenium masses m/z 80. The effects of the reaction gas species, flow rate and rejection parameter q (RPq) of the DRC system on signal-to-background ratio were studied. It was shown that the interference was eliminated when CH₄ was used as reaction gas with flow rate of 0.9 mL·min^-1, and RPq was 0.7. The proposed method had a wide linear range of 0.01~200 μg·L^-1 and a low limit of detection and quantitation (0.001 μg·g^-1 and 0.004 μg·g^-1, respectively). The relative standard deviation was 3.39% (n=7), and the recoveries were between 97.32%~101.1%. Validation of the method was carried out by determining Se in standard reference citrus leaves GBW10020. Good agreement was obtained between the certified value and the experimental result.

Key words: instrumental analysis, element determination, selenium