This thesis is divided into four parts. In the first part, the history of chromatography is described. Different modes of chromatography are briefly discussed and a survey of stationary phases being used in High Performance Liquid Chromatography (HPLC) is made. The need for a non-polar reversed-phase stationary phase is highlighted. A brief survey of the use of carbon by other workers in liquid chromatography is also made. The second part of the thesis deals with the production and structural study of porous graphitic carbon (PGC). the different stages of production of PGC are discussed. Pore volume and surface area studies on PGC have also been made. A detailed structural study of PGC has been presented. The third part of the thesis deals with the literature survey of the formation of surface complexes on carbon and the gas reactions of carbon, an understanding of which was necessary for the production and control of the final quality of PGC. The fourth part of the thesis deals with the use of PGC in HPLC. A packing method for PGC has been investigated. Different batches of PGC's produced have been tested with standard test solutes. A separation of a wide variety of solutes, including polymethylphenols, polymethylbenzenes, alkylbenzenes, bases, acids, polyaromatic hydrocarbons, pheynl ketones and phthalates on PGC have been achieved. Analgesics can also be separated. Solvent strengths on PGC have been investigated using different solvents and different solutes.

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The history of chromatography is described from Tswett's first experiments at the turn of the century to the sophistication of modern high performance liquid chromatography. The renaissance of liquid chromatography in the late sixties as a result of the development of chromatographic theory is discussed. The thermodynamics of the chromatographic process are outlined. Brief descriptions of the techniques of adsorption chromatography, liquid/liquid partition chromatography, ion-exchange chromatography, gel permeation chromatography and ion-pair chromatography are given. The development of theories of peak dispersion is discussed. The 'random walk' model of peak dispersion, developed by Giddings is outlined with particular emphasis on the isolation of three independently contributing terms to the overall peak dispersion. Studies of the variation in performance of Spherisorb alumina as a function of p^Lcking technique and column geometry are reported. The variation in performance with column geometry is related to the infinite diameter effect introduced by Knox and Parcher. The separation of aromatic sulphonic acids is reported using a novel form of ion-pair chromatography in which the hexadecyl-trimethylammonium ion is employed. Ion-pair chromatography was performed using two chromatographic supports: Partisil, an irregular porous silica and SAS, a chemically bonded stationary phase material produced by the Wolfson Liquid Chromatography Unit. Separations of some commercially important sulphonated food dyes and their intermediates are presented. A new equation is presented which relates the analysis time required for a separation in terms of the available pressure, the resolution required, the quality of the packing and to the properties of the solute and effluent. This equation is used to quantify the advantages of using very small particles in H.P.L.C. and this is illustrated by an experimental study of the effect of particle diameter on the efficiencies of columns packed with 6, 7.5, 10 and 20 micron Spherisorb alumina.

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Silica-based stationary phases have been under investigation since they were first produced, and studies still continue to try to improve their morphology and porosity. A handful of reliable and straightforward synthetic procedures are used routinely for their manufacture. The most widely applied procedures are variations of the modified Stober synthesis route that allow the manufacture of relatively monodisperse particles in the nanometer range, or the sol-gel route that produces larger porous microstructures. However, the controlled manufacture of silica stationary phase with the desired physical properties is still a challenge, and most of their preparation involves multi-step preparation, adding cost and time. This dissertation outlines work that introduces a set of new protocols that were developed for the preparation of silica with controlled morphology and porosity. Herein, silica microspheres with tuneable pore size and particle size distribution were synthesised using a modified Stober method. Hydrophilic polymers were introduced into the reaction system, which acted as stabilising agent. Further altering the reaction parameters resulted in the formation of silica microspheres with controlled surface morphology, beads-on-bead silica particles. The preparation conditions were extensively studied in order to understand the reason for such phenomena. The beads-on-beads particles exhibit chromatographic potential, especially for proteins separation. Moreover, porous silica microspheres were further used for the preparation of hierarchically porous silica monoliths by a controlled freezing approach. The macropore morphologies could be tuned with the addition of surfactants in the silica colloidal suspensions during the freezing process. The engineering of porosity and improvement on mechanical stability of the silica materials were achieved through a further soaking and sol-gel process. It was also possible to enhance the mechanical stability through thermal treatment of the materials. Directional freezing approach was also evaluated to direct the assembly of silica nanoparticles. The presence of water-soluble polymers resulted in better aligned features and acted as a gelling agent in the case of charged polymer. The monolith was successfully prepared inside a fused-silica capillary column and was investigated for chromatographic applications. Preformed emulsion-templated porous polyacrylamide beads and monolith were used as a scaffold for controlled growth of silica spheres on macroporous surface. A hierarchical hybrid structure was formed. The polymer scaffold could be removed to form porous silica spheres and macroporous structures. Further investigation was considered to control the porosity and the size of the forming microspheres. This study was further extended into the preparation of fluorescent silica spheres and composite materials. Furthermore, a simple and generic method was also developed for the preparation of gradient emulsion-templated structures. The gradient could be achieved with the aid of centrifugation mechanism. This method enabled the formation of dual gradient mesoporous and macroporous composites.

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Miniaturisation of chromatographic systems is becoming increasingly desirable. Future developments will demand the analysis of smaller samples, at faster rates, with increasingly complex separations required. These demands are already starting to exceed the capabilities of conventional HPLC systems. Systems will require more column efficiency, operation at higher flow rates and detection of the undiluted eluent in the most sensitive detectors available. CEC offers the opportunity to achieve these goals. The main obstacles to using CEC reliably are the relatively unstable nature of purely electrically driven flows in packed beds, the lack of good quality CEC columns and the lack of dedicated instruments to perform CEC analysis. Also, CEC shares some of the same problems with HPLC of miniaturising the separation system without incurring dispersion related losses. The work detailed in this thesis contributes considerable advancements in most of these areas. Novel methods to produce high quality columns are described. The work demonstrates effective methods for coupling CEC to MS that make allowance for control of dispersion. The thermal limits of operation are discussed and demonstrated. Pressure-assisted CEC, demonstrating the practicality of performing CEC based analysis that is as reliable as current HPLC systems is shown. Proper optimisation of these type of uses will ultimately deliver CEC in a reliable format which will encourage a whole new audience of users to reap the benefits available.

A new hydrophobic support material, Porous Graphitic (or Graphitised) Carbon (PGC) has been studied using both Liquid (LC) and Gas Chromatography (GC). The heat of adsorbtion (AH) of typical LC solvents determined on PGC, using GC, showed that AH increased with the molecular area (Ax) of solvents for well graphitised carbons, but that AH/Ax values were similar for all solvents studied. By definition, AH/Ax is a measure of eluotropic strength. The results reveal that a strong eluotropic series does not exist on carbon. A strong eluotropic series does exist on silica. In this case, AH/Ax values of solvents were dependent upon their eluotropic strengths (Eo), determined by LC. GC work was carried out using alcohols, ketones and aliphatic hydrocarbons on PGC, modified with different amounts of Carbowax 1500. Symmetrical peaks were obtained with coated materials. The column efficiency (N), first increased and then dropped with increasing Carbowax content on the PGC surface. The retention of ketones and hydrocarbons decreased with increasing amount of Carbowax on PGC. In the case of alcohols, the retention decreased with the initial introduction of Carbowax on to PGC. Some alcohols displayed enhanced retention at 0.10% of Carbowax. All alcohols showed increased retention at the monolayer coverage of Carbowax. In the quest for a perfect material for adsorption GC, PGC samples were hydrogen treated at elevated temperatures (230-1030°C). All hydrogen treated samples failed to display signficantly improved chromatographic properties. PGC was then treated with toluene in a stream of either hydrogen (at 630°C) or nitrogen (at 630°C or 300°C) to eliminate any active sites present on the surface. Hexane was used us an alternative to toluene at 630°C in a stream of hydrogen. Such surface treatments yielded improved materials for adsorption GC. On heating the columns (beyond 230"C), containing these materials, with carrier gas running through the columns, the Chromatography deteriorated in the cases of toluene-treated PGC whilst the Chromatography of the hexane-treatcd PGC remained unaffected. LC work on some aromatic compounds using PGC, coated with surfactants such as Tween 80 or Span 80 showed that, analyte retention decreased with increasing surfactant concentration (up to 0.03% of Tween and 0.02% of Span) in the eluent. N dropped with the introduction of Tween to the PGC. Increasing the ratio of water to mcthanol in the eluent, at a constant eluent concentration of surfactant, resulted in diminishing N, increasing eluent polarity and analyte retention values. Ion pairing was carried out on PGC using cetyltrimethylammonium-bromide (CTAB) as the ion pairing agent, at an eluent pH of 12.5. The retention of solutes, that ionise under these conditions, increased whereas the retention of analytes, that do not ionise, decreased with increasing eluent concentration of CTAB. The coated or chemically modified PGC surfaces are useful in GC whilst the dynamically coated PGC surfaces are important in LC. Such surface treatments can alter the following properties of PGC; (a) Retention characteristics, (b) the selectivity and (c) chromatographic efficiency.

Surface modification of porous graphite has been studied in detail by liquid chromatography. The non-polar nature of the graphite provides the basis for adsorptive modification by which the graphite surface is either deactivated or functionized. While the elimination of geometric heterogeneity is achieved by adsorption of trace polyaromatic compounds, the specialist in selectivity is conferred to the graphite by a monolayer coating of modifiers. A number of strategies are used for different purposes. These include dynamic coating, insoluble coating and cross-linked coating. The chromatographic properties of the modified materials are evaluated in terms of efficiency, selectivity and stability. With the exception for cross-linked coating, the modified materials show performances better than those of the original graphite. Applications to adsorption, ion exchange, chiral and exclusion chromatography are demonstrated. These new packings are found particularly useful in the separation of inorganic anions, amino acid and hydroxy acid enantiomers. They give excellent peak symmetry and long term stability. The mechanisms of retention on the graphite based materials are characterised and discussed.