Applications of Gas Chromatography-Mass Spectrometry to Organic Chemistry

Middleditch, B. S (1971) Applications of Gas Chromatography-Mass Spectrometry to Organic Chemistry. PhD thesis, University of Glasgow.

Abstract

The work described in this thesis was based on applications of the combined technique of gas chromatography-mass spectrometry (GC-MS) to a variety of topics in organic chemistry and biochemistry. The research included studies of the scope of the technique (based on model compounds) and applications to actual analytical problems. Following the introduction, a section of the thesis is devoted to work on steroids. Results obtained with progesterone and testosterone analogues confirm The value of GC-MS in distinguishing isomers. The use of trimethylsilyl (TMS) ether derivatives in GC-MS is well established, but the advantages of (chloromethyl)dimethylsilyl ethers as derivatives for GC-MS have been little explored. The utility of these derivatives is illustrated and discussed for the example of 1/alpha-alkyl-17beta-hydroxy steroids. The mass spectral fragmentations of TMS ether derivatives of androst-5-en-3beta-ol analogues and of other unsaturated 3beta-hydroxy steroids have been investigated. The results of this survey have been applied to the characterisation of yeast sterols, sterols from a bacterium (Methylococcus capsulatus) grown on methane, steroidal drug metabolites, and a steroidal enzyme-reduction product. Corticosteroids cannot be examined directly by GC-MS because of References cited in this summary are restricted to publications incorporating work described in the thesis. the low thermal stability of the side chain. Earlier work has shown that their boronate derivatives are quite stable. The mass spectra (recorded by GC-MS) of representative corticosteroid boronates are discussed in respect of their use in structural assignments. Similar difficulties are encountered in GC-MS of beta-hydroxy amines because of their relatively high polarity and low thermal stability. The use of boronate derivatives in the characterisation of catecholamines and related beta-hydroxy amines by GC-MS is discussed, and a more detailed investigation of the mass spectral fragmentations of the derived 1,3,2-oxazaborolidines has been carried out. O-methyloxime (MO) derivatives are of value in the analysis by GC-MS of aldehydes and ketones. Salient features of the spectra of MO derivatives of aliphatic aldehydes and ketones are enumerated. Aldehydes from the cuticular leaf waxes of Chenopodium album L. and Lolium perenne L. have been identified by GC-MS of their MO derivatives. Unsaturated aliphatic hydrocarbons from the green form of the freshwater alga Botryococcus braunii have been ozonised and cleaved to form aldehydes which have been identified as their MO derivatives. The structures of the hydrocarbons have thus been inferred. An exploratory study of the use of GC-MS in the analysis of air pollutants has been carried out. The gas chromatographic and mass spectrometric properties of some polycyclic aromatic hydrocarbons have been surveyed and a number of these compounds have been tentatively identified in dust collected from air conditioner filters. Perfluorodecalin has been found to be a convenient mass calibration standard for low resolution mass spectra. The need for, and problems associated with, computer-assisted data handling in GC-MS are discussed. The development of an on-line real-time data acquisition system is described.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Organic chemistry, Analytical chemistry
• Date of Award: 1971
• Depositing User: Enlighten Team
• Unique ID: glathesis:1971-78555
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 28 Feb 2020 12:09
• Last Modified: 28 Feb 2020 12:09
• URI: https://theses.gla.ac.uk/id/eprint/78555