Abstract

In this work, we have studied the synthetic insecticides imidacloprid and chlordimeform on both oxidized and metal- lic tungsten thermoemitters in electric fields of E<10 5 V/cm using surface (thermal) ionization mass spectrometry. Imidacloprid (1-(6-chloro-3-pyridylmethyl)-N-nitroimidazol-2-ylideneamine) is a neurotoxic insecticide of the neonicotinoid family and is one of the most widely used in agriculture. Chlordimeform is a carboxamidine, classified as both a formamidine insecticide and acaricide, as well as a member of monochlorobenzenes. The experiments were conducted using the MI 1201 B magnetic static mass spectrometer, which was specifically modified for the surface ionization method. The studied samples were efficiently ionized on the oxidized thermoemitter, and the mass spectra consisted of M + , [M-H] + , [M-H-2nH] + and [M-R] + ions. On the metallic ther- moemitter, the mass spectra consisted of fewer lines compared to those obtained on the oxidized surface, indicating that no addi- tional ions were generated. The mechanisms of ion formation on both oxide and metallic surfaces were discussed. For the first time, the ionization energies of the major ions of the studied compounds were evaluated using the surface ionization method, as well as the heat of sublimation of the molecules. Unimolecular decays were detected in the mass spectrum of chlordimeform. The surface ionization mass spectrometry data of samples was compared with the gas chromatography-mass spectrometry data.