| Summary: | When a mass spectrometer is operated at pressures greater than 0.3 Tort, a series of ion-molecule reactions occur. The reversed geometry ZAB-2F instrument used for this study has the unique feature that these complex ionic species formed may be separated and studied by the mass analysed ion kinetic energy (MIKE) technique. Firstly, the processes within the ion chamber were investigated to determine the means by which ions are extracted under high pressure conditions and the expected lifetime of ions before they leave the source. Some special instrumentation was required for the accurate control and measurement of high pressure and the design and construction of a "baratron" automatic pressure regulating and measuring system has been fully described in this thesis. Several classes of ion-molecule reactions have been studied and these include proton transfer, group transfer and charge permutation reactions. New ions formed by ion-molecule reactions of benzene in the source have been investigated by the MIKE and linked scan techniques i.e. the structure of the [2M-1]+ ion. A series of polyfunctional molecules was studied to see whether molecules containing, for example, two nitrogen atoms e.g. indazoles, imidazoles could be used to give information on the site of protonation or ethylation when the [M+l] + and [M+29]+ ions are formed under chemical ionisation conditions. Various isomeric compounds were protonated and ethylated in this way and the structures of the resulting ions cot-pared and contrasted to give structural information. Excited organic ions may be formed by charge exchange reactions and by selecting the rare gas used for ionisation, the internal energy given to the molecule could be varied. This was illustrated for a range of rare gases.
|
|---|
