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Title: Studies of supercritical fluid technology for benzodiazepine analysis, LC-MS for ecdysteroid screening and DCT spectroscopy of chloromethanes and bromomethanes
Author: Grant, R. P.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1998
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The aim of the investigations was to evaluate the potential of a number of analytical techniques for studying various compound classes. The techniques employed in this study include supercritical fluid extraction (SFE), supercritical fluid chromatography (SFC), gas chromatography hyphenated to mass spectrometry (GC-MS), liquid chromatography hyphenated to mass spectrometry (LC-MS) and double-charge-transfer (DCT) spectroscopy. Chapter 1 reviews the properties of supercritical fluids and the historical developments of SFE and SFC. The fundamentals of chromatography, mass spectrometry and interfacing systems are also described, in particular, electrospray (ES) and atmospheric pressure chemical ionization (APCI) interfaces. Evaluation of qualitative SF for benzodiazepine screening and off-ine quantitative SFE-SFC-UV for the analysis of benzodiazepines in biological matrices is described in chapter 2. An improvement in the chromatographic efficiency and speed is shown for complex benzodiazepine mixture separation by SFC and a review of current analytical methodologies is reported. The use of GC-MS as a more sensitive detector for quantitative off-line SFE analysis is also shown, allowing comparison with the off-line SFE-SFC-UV assay described. In chapter 3, the utility of LC-MS is investigated in the screening of plant samples for ecdysteroids. Both ES and APCI interfaces are evaluated together with normal and reverse phase LC systems. The enhanced sensitivity and specificity of LC-MS-MS is also shown, along with a comparison with current state-of-the-art analytical methodologies described in the literature for analysis of ecdysteroids. Chapter 4 describes the use of DCT spectroscopy to gain information on ground and excited dication electronic states of chloromethanes and bromomethanes. Application of a semi-empirical computational method is also reported and consistently good agreement is obtained between measured and calculated double-ionization energies to singlet and triplet electronic states of the dications. Chapter 5 describes the instrumentation used in the investigations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available