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This thesis contains details of experiments involving the use of supercritical fluids (SCF) and high pressure liquids acting as antisolvents and transport media. The thesis is divided into six Chapters, each detailing different aspects of SCF technology. Chapter 1: Provides the reader with general information concerning the properties of supercritical fluids. Information is given concerning the use of SCFs as solvents and antisolvents. Reviews of the PCA and GAS processes are also provided. Chapter 2: Describes the initial study of the preparation of C60(gas) intercalation compounds. PCA generates compounds of C₂H₄, C₂H₆, C₃H₆ and C₃H₈, which were characterised by JR. A novel GAS technique is used to allow collection of PXD, SEM and MAS ¹³C NMR data of these compounds. Chapter 3: Details a novel supercritical antisolvent technique which allows the generation of macroscopic crystals of intercalate species C60(C₂H₄) and C60(C₂H₆). Crystallographic data on these compounds is presented. Datasets for the intercalates C60(CO₂), C70(C₂H₆) and C70(CO₂) were also collected. Chapter 4 Contains preliminary information on the formation of ‘nanopeapods', that is, carbon nanotubes filled with C60. A new route to the formation of these materials at room temperature is shown. Chapter 5: Describes the impregnation of mesoporous silica with aluminium containing species using SCF as a solvent. Materials display unprecedented stability to steaming with high retention of structural ordering and surface area. Chapter 6: Describes the extraction of template molecules from mesoporous silica. The possibility of complete removal of surfactant using a SCF is shown. The effect of temperature and pressure effects are also measured. Appendices are available at the back of the thesis to describe the equipment, analytical techniques and some safety principles for use of SCF.

The use and supply of various organic solvents for analytical chemistry is coming under scrutiny due to their environmental impact. International legislation now prevents the supply of "ozone depleting" solvents for laboratory purposes. Consequently alternative analytical methods to those which had previously relied upon the use of a range of organic solvents need to be developed. Supercritical fluids exhibit some properties associated with gases and liquids, and in particular their solvating characteristics are equivalent to a wide range of conventional organic solvents. Environmentally benign carbon dioxide in its supercritical fluid state can be utilised to imitate the solvating power of a range of organic solvents from non polar pentane through to more polar pyridine. There are many reports detailing the use of supercritical fluid extraction for the isolation of target compounds from a very wide range of solid matrices. The objective of these studies was to develop direct liquid supercritical fluid extraction procedures using carbon dioxide to isolate, concentrate and quantify target analytes from aqueous media. These investigations involved using off-line and on-line supercritical fluid extraction procedures with final analytical detection and quantification being accomplished using a range of chromatographic, spectroscopic and mass spectrometric methods. Within chapters 2 and 3, an alternative infrared method for determining the quantity of oil in process and discharge waters is described. The results of quantification studies involving various oils and hydrocarbons indicate that the custom built supercritical fluid extraction system developed for these investigations directly coupled with an infrared spectrometer provide an alternative method to traditional liquid-liquid extraction procedures that involve the use of ozone depleting and/or toxic organic solvents. Chapter 4 describes how direct aqueous supercritical fluid extraction was used to continuously isolate free testosterone as it was liberated during the enzymic digest of a testosterone-/3-D-glucuronide solution incubated with Helix pomatia glucuronidase. Other studies described within this chapter that also involved the use of direct aqueous supercritical fluid extraction with off-line gas chromatography-mass spectrometry describe procedures for determining trace levels of organophosphate pesticides and polyaromatic hydrocarbons in aqueous samples. The development and use of on-line direct aqueous supercritical fluid extraction coupled with supercritical fluid chromatography-mass spectrometry using atmospheric pressure chemical ionisation for the analysis of phenols at the ppb level is described in Chapter 5. Chapter 6 describes the use of direct aqueous supercritical fluid extraction coupled online with liquid chromatography-mass spectrometry using ammonia chemical ionization for the analysis of three veterinary drugs at the ppb level. Results of off-line and on-line studies involving electrospray tandem mass spectrometry with high pressure liquid chromatography for the analysis of a range of ionophores at the low ppb level following their isolation using direct aqueous supercritical fluid extraction are also presented.