The development of linked scan techniques in mass spectrometry

• Main Author: Porter, C. J.
• Published: Swansea University 1980
• Subjects: 543.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638554

The technique of simultaneously scanning the magnetic (B) and electric (E) sector fields of a double focusing mass spectrometer such that a particular relationship is maintained between them is the basis of this thesis. This technique is termed linked scanning and the two more important scans, that is, the constant B/E and B2/E linked scans are discussed in detail and compared with the numerous other methods of scanning that can be used to observe products of unimolecular and collision-induced fragmentation in any field-free region of a mass spectrometer. These linked scans, are not limited to any particular instrumental geometry and should be effective on any of the mass spectrometers widely used in university and industrial research, although the work described in this thesis was performed on the prototype Vacuum Generators ZAB-2F mass spectrometer. This type of instrument is referred to as "reversed geometry" where the ions pass through the magnetic sector prior to entering the electric sector. Development of the necessary circuitry for scans in which B/E or B2/E is maintained constant, improvement of the linearity of the Hall probe magnetic field sensing device used, recognition of artefact peaks and improvement of the resolution of peaks at constant B/E are discussed in detail. In addition, methods of improving the amount of dishing of broad metastable peaks arising due to fragmentation processes in the first field-free region have also been included. Precollimation of the ion beam before fragmentation is shown to contribute greatly to the discrimination effect leading to dishing.