Field desorption mass spectrometric analysis of organic compound residues in the environment. I--Organochlorine insecticides.

Field desorption mass spectrometry is applied to the positive identification of organochlorine insecticides and their related compounds residing in field soil environment. Additionally, standard field desorption mass spectra of these compounds are presented. Soil samples were collected in lettuce and spinach fields, and insecticides were extracted, cleaned up, and separated with thin-layer chromatography. Residue levels were measured by injecting the extract into a gas chromatography equipped with an electron capture detector. Residues of p,p'-DDT and dieldrin in field soil samples were clearly identified by field desorption mass spectrometry using the emitter dipping method. Moreover, mixed residues of these insecticides were simultaneously confirmed. However, residues of insecticides and their related compounds other than p,p'-DDT and dieldrin could not be characterized. All spectra of standard showed prominent [M].+, [M(35Cl(n-1), 37Cl)].+ and [M(35Cl(n-2, 37Cl2)].+ ions, and the [M(35Cl(n-1), 37Cl)].+ ion was the base peak in all spectra obtained.