Use of a Particle Beam Interface Combined with Mass Spectrometry/Negative Chemical Ionization to Determine Polar Herbicide Residues in Soil by Liquid Chromatography

The use of mass spectrometry/negative chemical ionization (MS/NCI), in combination with selected-ion monitoring, allows sensitive and selective determination of polar and thermally unstable herbicide residues by liquid chromatography coupled to a particle beam interface. The method has been applied to the analysis of soil samples for herbicide residues, using various procedures for their extraction and employing matrix-standard calibration to avoid quantitative errors due to transfer of matter through the interface. Data for the fragment ions found in the MS/NCI procedure and chromatograms from analyses of real samples are also presented.

The investigation of N‒dinitrophenyl derivatives of amino acids by electron/chemical ionization using a particle beam interface1

The EI and CI mass spectra of DNP‒amino acids and oligopeptides give characteristic mass spectra when a particle beam interface is used for introduction. They differ from mass spectra obtained after direct insertion into the ion source: In the particle beam interface the major part of the molecules suffers degradation by contact with metal surfaces such as decarboxylation and reduction of the nitro groups. The final products are benzimidazole derivatives carrying in 2‒position the residue of the respective amino acid. These products show characteristic fragmentation reactions which allow to identify isomeric amino acids. For DNP‒di‒ and oligopeptides an identification of the N‒terminal amino acid is always possible, that of the C‒terminus with restrictions.