Inhaled particulate matter (PM), containing bioaccessible potentially toxic elements (PTE) has attracted attention due to potential human health risk. This study was to develop and assess the suitability of simplified bioaccessibility extraction test (SBET) and the stomach phase of unified bioaccessibility method (UBMSG) to measure bioaccessible PTE in PM10 collected on filter dynamic measurement system (FDMS) filters used worldwide. Analytes were As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn and measured by ICP-MS.The SBET and UBMSG were miniaturised for application to PM10. Reducing sample mass and reagents volume by a factor of 10 for the SBET and by a factor of 6 for UBMSG, and presence of the FDMS filter did not affect PTE extractabilities. Bioaccessible PTE in blank FDMS filters were generally low, except for Zn. Washing acrodisc® syringe filters immediately before use with 80 mL of glycine reduced the concentration of Cu and Zn in procedural SBET blanks from 119 and 1520 to 0.129 and 14.5 μg L-1, respectively. New closed-loop and single-pass dynamic models for the SBET and UBMSG either coupled or not with ICP-MS were successfully applied to determine bioaccessible PTE in real and simulated PM10 samples. Accuracy of models was ascertained by mass balance, and verified by Z-scores, which were generally acceptable. For single-pass models, rapid mobilization was observed for PTE, except for Cr. Finally, a new artificial mucus fluid was applied sequentially with the SBET and UBMSG (gastric fluid only) to measure bioaccessible PTE in inhaled PM10. Bioaccessible PTE concentrations, which were underestimated for As, Cr, Cu, and Pb, and overestimated for Cd, Fe, Ni and Zn using ingestion route alone, were more accurately determined. Extraction methods that are more similar to real body processes were successfully created to determine bioaccessible PTE in PM10 that are inhaled and subsequently ingested.

One of the current challenges in chromatography is the fast separation of large biomolecules. The demand for this is huge in pharmaceutical and biological research. To meet this challenge a new type of porous, large pore support material is required. A new, unique type of silica support, named spheres on sphere (SOS) silica, has recently been discovered which may meet these demands. SOS particles are produced via a one-pot synthesis and are comprised of a nanoparticle shell surrounding a larger core microsphere. High performance liquid chromatography (HPLC) columns packed with such particles have shown remarkably fast separation of proteins. These new particles show high potential as a revolutionary HPLC technology compared to widely used core-shell silica particles, which are prepared by a tedious layer by layer procedure and suffer with the issue of poor mass transfer for large analytes. This thesis outlines the experimental work undertaken to develop SOS particles which are specifically designed for the separation of proteins and large molecules using HPLC. The synthesis method has been optimised to achieve particles with a complete, densely packed, single-layer shell and a diameter suitable for use in HPLC. Additionally, a narrow particle size distribution is achieved, removing the need for a time-consuming and wasteful classification process. The suitability of microwave irradiation for the surface functionalisation of silica materials has been investigated. This includes the development of a bonding method for SOS particles which is shown to be highly reproducible and capable of providing comparable bonding density to conventional reflux heating methods. The use of microwave heating also results in significantly shorter reaction times and lower power consumption compared to commonly used equipment such as hot plates or heating mantles. Following surface functionalisation, the performance of HPLC columns packed with SOS particles have been assessed in both isocratic and gradient elution mode. Parameters such as column permeability, total porosity and impedance have been determined in isocratic mode, which allows direct comparison with other column packing materials. In gradient elution mode the SOS columns have been used for the analysis and separation of a wide range of peptides and proteins. Excellent performance has been obtained using the SOS material where fast gradient analysis is applied, in some cases outperforming a commercial core-shell column specifically designed for protein analysis.

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No description available.

A review with 133 References of the application of vibrational spectroscopy at high pressures to the study of solids is given, Two new designs of diamond anvil cell (DAC) are described and compared with designs of others. The use of the DAC in combination with various spectroscopic instruments is described and the calibration of the cell, taking into account the pressure gradient present across the anvil faces, is reported. The spectroscopic and physical properties of two anvil materials, diamond and sapphire, are described with particular attention being paid to the fluorescence properties of various types of diamond under laser excitation. Another design of high pressure cell, which applies hydrostatic pressure to samples, is reported for use in Raman spectroscopy. The main area of compounds investigated at high pressures using the DAC were complexes of the type A2IMX6 (A = monatomic cation, X = halogen). A wide range of these materials were studied in the far-i.r. and members of the series A2IPtCl6 were also examined in the Raman. For the latter compounds symmetry species were related to observed pressure sensitivities of vibrations. Unusual behaviour of the v4 bending mode at elevated pressures was found for complexes where M possessed a lone pair of electrons. Possible mechanisms to account for the behaviour of the mode are discussed. Some hexammine salts of cobalt and nickel halides were also examined both at liquid nitrogen temperature and at high pressure respectively. The appearance of an ammonia torsion mode at liquid nitrogen temperature is shown. An attempt to obtain quantitative results from the observed pressure dependencies was not possible owing to the nature of the complexes examined.

The aim of this work has been to design and develop a series of new NMR tools and data analysis techniques to measure diffusion, and in particular, restricted diffusion within heterogeneous systems. This area of research has many different applications in medicine and the pharmaceutical, oil-recovery, food, and chemicals industries. The information about fluid filled structures, be they cells, rock pores, or emulsions, and how these may alter under different conditions, is of great interest. The work covered in this thesis is grouped into three sections, where in all cases constant, static magnetic field gradients are used, either by choice or necessity, for encoding diffusion. The first section covers the design and development of a technique to isolate the signal of restricted diffusing spins from that of freely diffusing spins. This results in a more accurate and robust technique for quantifying restriction parameters relating to the size and structure of the restricting barrier. The second study approaches the problem of measuring diffusion in heterogeneous environments where differences in magnetic susceptibility of the constituent parts gives rise to strong internal magnetic field gradients. Traditional techniques try to overcome these gradients in a manner of different ways. Here, the intrinsic gradients are poacher turned game-keeper, and used themselves as the diffusion encoding gradients. The final study again uses large constant magnetic field gradients. Here, the fringe field of a superconducting magnet is used. Different pulse sequences and techniques are modelled and used experimentally to demonstrate how liquid diffusion coefficients may be measured, and it is shown that simple pulse sequences which do not allow for relaxation lead to inaccuracies.

Laser-induced fluorescence (LIF) spectroscopy has been used to probe the properties of several metal-containing free radicals, prepared in a supersonic jet expansion by either an electrical discharge or by laser ablation/photolysis. The first spectroscopic observation of the zinc monoethyl radical was carried out following an electrical discharge through a mixture of zinc diethyl and helium. The laser excitation spectra recorded contained extensive vibrational structure, and a partial assignment is presented with the aid of ab initio SCF calculations. This was the first time an electrical discharge had been used to prepare a binary organometallic intermediate in a supersonic jet. LIF excitation and dispersed fluorescence spectra of the MgCCH free radical were obtained following laser ablation of magnesium metal in the presence of methane. This was the first observation of the electronic spectrum of MgCCH, and vibrational progressions in the metal-carbon stretching mode were assigned for both the X˜2sum+ and A 2pi electronic states. Other weak vibrational structure attributable to metal-carbon bending and carbon-carbon stretching modes is also tentatively assigned. In addition, the rotational constant was found for the A 2pi state following a simulation of the observed rotational structure. Laser ablation of calcium and strontium in the presence of benzene gave intense LIF spectra of several well-known and one unknown species. Subsequent analysis of the observed vibrational structure led to the conclusion that the CaCCCH3 and SrCCCH3 free radicals were the spectral carriers, respectively. This task was aided by a series of density-functional theory calculations. This is the first spectral observation of both species. Initial attempts at characterising the alkali metal monoxides by LIF spectroscopy are also presented. These intermediates were to be prepared by laser ablation of the corresponding metal in the presence of N2O. Early experiments focused on the monoxides of Li and Na, and currently only Li + N2O has produced an LIF spectrum. The observed structure, which is quite complex and not amenable to any simple assignment, has been tentatively assigned to the C2pi -- X2pi and C2pi -- A2sum+ systems of LiO. These preliminary findings bode well for future studies of the heavier alkali monoxides.

The role of ion insertion into the electrochromic metal oxide WO3 has been studied using a combination of electrochemical, gravimetric and spectroscopic techniques. The electrochemical quartz crystal microbalance (EQCM) was used to investigate the effect of electrolyte composition by studying the identity of the cations and anions involved and the concentration of the electrolyte used. It was found that the effect of electrolyte concentration and choice of anion did not affect film reduction and re-oxidation. The two cations studied, Li- and Na+, however cause marked differences in film redox behaviour. The effect of film history was studied using a combination of EQCM and spectrophotometry. The initial cycle at a slow scan rate (5 mV s-1) showed responses different to those of subsequent cycles. Results indicated that at completion of the first cycle there is both injected charge and mass remaining in the WO3 film. This effect has been termed the "break-in" effect and has been seen for all experiments initially cycled at this slow scan rate, irrespective of anion or cation, or the electrolyte concentration. It is possible to correlate current (or charge), mass change and absorbance data together in a novel way, to give information regarding electrons, ions and solvent and electron and ion distribution (via the extinction coefficient, ). Also, the effect of long term cycling (>10,000 cycles) has been investigated with respect to cation insertion. This shows that Li+ insertion yields stable WO3 films after many cycles, whereas Na+ insertion does not. The effect of experimental time scale also has been studied using cyclic voltammetry and chronoamperometry, together with the EQCM. Again, the "break-in" effect was recorded using chronoamperometry, indicating that the effect is not only seen for cyclic voltammetric experiments. Under all experimental conditions used, there is a second, neutral species being inserted and extracted alongside the cations.

This thesis describes the quantification of biogenic and anthropogenic trace gases using the highly sensitive spectroscopic technique of broadband cavity enhanced absorption spectroscopy (BBCEAS). This technique uses a high finesse optical cavity to make absorption measurements over extended path lengths within a compact instrument and over wavelength ranges that are sufficiently broad to enable several overlapping absorbers to be quantified simultaneously. Here, BBCEAS was applied to measure I₂ emissions in coastal regions, NO₂ in urban ambient air, and VOC oxidation products during experiments in an atmospheric simulation chamber. Much of the work used a novel, mobile, battery-powered BBCEAS system to measure gas concentrations in very close proximity to their emission sources. The dominant emission source of iodine into the atmosphere in coastal regions comes from intertidal macroalgal beds. Gas-phase iodine chemistry perturbs the HOₓ and NOₓ radical cycles, provides additional sink reactions for tropospheric ozone, and initiates nucleation of new aerosol particles. Results are presented from an extensive laboratory study of I₂ emissions from five species of temperate seaweeds. Time- and species-dependent I₂ emission rates were quantified in studies mimicking the progressive exposure of seaweeds to air around low tide. Seasonal differences in I₂ emission rates were investigated. By deploying the BBCEAS instrument from a boat, I₂ concentrations were also measured directly above Laminaria digitata and Ascophyllum nodosum seaweeds growing in their natural habitat. NOₓ emissions affect urban air quality directly and indirectly (the latter via formation of tropospheric ozone and secondary aerosol). BBCEAS was applied to measure NO₂ and the optical extinction from aerosol particles at locations around the Leicester University campus. BBCEAS results were compared with commercial NOₓ (chemiluminescence) and aerosol instrumentation. The mobile BBCEAS instrument was also deployed to investigate the dispersion of NO₂ from the roadside.

Introduction: A biosensor may be described as a sensor incorporating a biological element such as an enzyme, antibody, nucleic acid, microorganism or cell. A biosensor should exhibit both shelf-stability and operation stability. Compatible solutes from hyperthermophilic bacteria, called hypersolutes, are very efficient for the preservation of the performance of a wide variety of biomaterials; ranging from proteins to whole cells and artificial tissues. The overall objectives of this work have been to investigate the application of hypersolutes to enhance the performance of biosensors based on the stabilization properties offered by hypersolutes compounds, particularly with respect to storage and operational lifetime. Materials and Methods: The stabilizing agents considered for this study were firoin, firoin A, ectoine®, hydroxyectoine, diglycerol phosphate (DGP) and potassium mannosyl-lactate (PML), provided either by Bitop AG (Witten, D) or StabVida (Oeiras, P).The following enzymes were selected due to their commercial importance: Glucose oxidase (GOx), alcohol oxidase (AOx), acetylcholinesterase (AchE) and lactate dehydrogenase (LDH). On immunosensors, a model system was first designed using ELISA tests. The influence of hypersolutes was then studied using BIAcore. The antibody test system selected for examination of the effect of stabilizing agents on immunosensor performance was based on an anti-human immunoglobulin G (IgG) primary antibody, grown in goat, and an anti-goat secondary antibody conjugated to horseradish peroxidase enzyme. A model DNA binding system was sought: The poly-A strand was tethered to the sensing surface within the BIAcore system via a biotin-streptavidin linkage whereas the complimentary poly-T strand contained a fluorescent Cy3 label, that offered the possibility to also use more conventional detection techniques to ensure thathybridization between the two complimentary strands had been achieved, as well as add a significant weight to the strand, increasing its visibility on the BIAcore signal.