Determination of neonicotinoid sulfoxaflor residues and stereoselective degradation in Pu-erh tea and Black tea by liquid chromatography-high-resolution mass spectrometry

The stereoisomer behavior of sulfoxaflor was investigated liquid chromatography-high-resolution mass spectrometry during Pu-erh tea and Black tea processing. Stereoselective separation of the analytes was successfully achieved on Chiral Cel OJ-3R. Individual optically pure stereoisomer was unstable. For 2S, 3S-sulfoxaflor, the conversion resulted in the formation of 2R, 3R-sulfoxaflor, a 1:1 mixture of two enantiomers 2S, 3S/2R, 3R-sulfoxaflor after 12 hr, whereas for 2R, 3R-sulfoxaflor, the conversion led to the production of 2S, 3S-sulfoxaflor, a 1:1 mixture of two enantiomers 2R, 3R/2S, 3S-sulfoxaflor after 30 hr, so the conversion rate of 2S, 3S-sulfoxaflor was 2.5 times faster than that of the 2R, 3R-sulfoxaflor. The degradation result showed no stereoselectivity of sulfoxaflor in Pu-erh tea or Black tea processing. Practical applications Sulfoxaflor is superior to the currently used best sap-feeding insecticides of imidacloprid in tea, which is used as an insecticide to control Empoasca pirsuga Matumura in Yunnan tea plantation. To the best of our knowledge, there is no report about a method for the determination of stereoselectivity of sulfoxaflor in tea. So a new analytical method to determine stereoisomer of sulfoxaflor in Pu-erh tea and Black tea processing using liquid chromatography-high-resolution mass spectrometry was firstly developed and applied to investigate the stereoselective sulfoxaflor degradation during Pu-erh tea and Black tea processing. It is applied to assess the fate and food safety of these enantiomers in tea.