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Maximum Entropy data processing techniques have been widely available for use by NMR spectroscopisis and mass spectrometrisls since they were first reported as a tool for enhancing damaged images. However, the techniques have been met with a certain amount of scepticism amongst the spectroscopic community; not least their apparent ability to get something for nothing. The aim of the work presented in this thesis is to demonstrate that if these techniques are used carefully and in appropriate situations a great deal of information can be extracted from both NMR and mass spectra. This has been achieved by using the Memsys5 and Massive Inference algorithms to process a range of NMR and mass spectra which suffer from some of the problems which are commonly encountered in spectroscopy, i.e. poor resolution, poor sensitivity, how to process spectra with a wide range of peak widths. The theory underlying the two algorithms is described simply and the techniques for selecting appropriate point spread functions are outlined. Experimental rather than simulated spectra are processed throughout. Throughout this work the Maximum Entropy results are freated with scepticism. A pragmatic approach is employed to demonstrate that the results are valid. It is concluded that the Maximum Entropy methods do have their place amongst the many other data processing strategies used by spectroscopists. If used correctly and in appropriate situations the results can be worth the investment in time needed to obtain a satisfactory result.

No description available.

There are many methods available for a laboratory analyst to measure the amount of a target analyte within an environmental sample containing a wide variety of other species. However the vast majority of these methods require expensive instrnmentation and the analyst to be trained in its operation and safety procedures. The aim of the following work was to produce a method of analysing environmental pollutants within a complex matrix, without, or with minimal sample pretreatment, using standard colorimetric methods. Results of the analysis would be displayed clearly within a short time and with a high degree of accuracy, selectivity and sensitivity. The tests could be used by an untrained operator and would not contain significant amounts of toxic or irritating chemicals. All the reagents required for the determination and removal of interferences would be contained within the test in the order required by the procedure. The tests would be capable of mass production and would have a shelf life of at least 9 months. TI1e following work describes the research carried out to meet the above criteria. The species of environmental interest investigated are aluminium, silver, molybdenum, sulphur dioxide and nitrogen dioxide. These species were chosen for reasons which will be mentioned in greater depth in the introduction. The tests are, however, not developed with a view to replacing existing instrumental methods, but as means for an operator to determine whether their sample requires further analysis using instrumentaion. TI1e aim of the test result is to provide the operator with the answer to questions such as does my tap water contain more than the recommended limit of aluminium? or does the effiuent from my photographic laboratory contain an amount of silver which could lead to my prosecution?. The operator when given a measurement from the tests, by comparing with a colour chart, for example, 0.1ugml-1, may then decide if they need further analysis using for example, ICP MS techniques. The development of both paper dip tests and a novel soluble polymer reagent delivery system are described, as well as capillary fill and dry reagent tube devices.The successful soluble polymer matrix test (SPMT) is also applied to develop a stripping voltammetric sensor for the detennination of lead in whole blood. It is hoped that the SPMT will negate the need for pretreatment of the blood sample before detennination.

Multidimensional ion mobility (IM) and mass spectrometry separations have been applied successfully to the analysis of a wide range of analytes and demonstrate potential as a selective and high throughput analytical technique. The direct analysis of pharmaceutical formulations from non-bonded reversed-phase thin layer chromatography (RP-TLC) plates by desorption electrospray ionisation (DESI) combined with drift tube ion mobility-mass spectrometry (IM-MS) has been investigated. The detection of active pharmaceutical ingredients is demonstrated with, and without, chromatographic separation of the active ingredients and formulation excipients. Varying the solvent composition of the DESI spray using a gradient allows selective desorption of pharmaceutical ingredients from the surface of the RP-TLC plate. The potential of IM-MS in combination with high performance liquid chromatography (LC) for the metabonomic analysis of rat urine is reported. The approach allowed the acquisition of nested data sets, with mass spectra acquired at regular intervals during each IM separation and several IM spectra acquired during the elution of an LC peak. The application of LC combined with field asymmetric waveform ion mobility spectrometry (FAIMS) and ion trap mass spectrometry to a metabonomic study of rat urine, with subsequent data mining by artificial neural networks, allowed discrimination between young and old rats on the basis of LC-FAIMS-MS profiles. The application of IM-MS to real-time reaction monitoring has also been investigated. Real-time reaction monitoring was carried out over a period of several hours, with the reaction mixture sampled and analysed at intervals of several minutes. Results indicate that spectral quality is improved when employing IM-MS, compared to mass spectrometry alone, as the complexity of the reaction mixture increases with time. The combined IM-MS approach has potential as a rapid and selective technique to aid pharmaceutical process control and for the elucidation of reaction mechanism.

Since the inception of analytical supercritical fluid extraction (SFE) in the early 80's, this technique has garnered great attractions in the extractions of variety of analytes from variety of matrices. In this study. supercritical carbon dioxide (SC CO2) has been examined as a sample preparation method for the extraction of eugenol from plant matrix prior to high performance liquid chromatography (HPLC) analysis and for the extraction of organochlorine pesticides (OCPs) from sewerage sludges and chlorpyrifos from formulation and soil samples prior to capillary gas chromatography (GC) analysis. This is an area of considerable interest as many current methods use environmentally hazardous chlorinated solvents and alternative methods are required. Although numerous studies have examined the potential application of SFE to isolate pesticides and plant products, the work has been qualitative rather than quantitative. The present work describes studies which have examined the supercritical conditions needed for complete extraction of the pesticides and plant product eugenol. Initially a complex matrix sludge was chosen. Later a simple matrix soil was chosen and a single pesticide chlorpyrifos was used as the SFE of sludge was unsuccessful. In the extraction of chlorpyrifos problems were encountered in the trapping of the extract on depressurisation of the SC CO2. The effect of collection solvent, CO2 flow rate, solvent depth, and restrictor heating on the trapping efficiency have been investigated. Two methods of trapping were evaluated. Once a quantitative trapping method was established, the effect of different soil matrices on the recovery of chlorpyrifos at different chlorpyrifos spiking level was investigated. The SFE of soil was compared to Soxhlet extraction.

This study has involved the analysis of volatile fingerprints using a hybrid electronic nose (e-nose) to discriminate between and diagnose the microorganisms which cause ventilator–associated pneumonia (VAP), one of the most important infections in the hospital environment. This infection occurs in hospitalised patients with 48-72 hrs of mechanical ventilation. VAP diagnostics still remains a problem due to the lack of a precise diagnostic tool. The current tests are mostly based on quantitative cultures of samples from the lower lung airways with clinical findings, which do not often result in accurate diagnoses of the disease. Cont/d.

This project describes development and problem solving efforts to realise a viable portable sensor for arsenic, applicable to drinking water. The work is the first dedicated effort towards this goal, after the preliminary investigations previously conducted at Cranfield University (Cooper, 2004 and Noh, 2005). Using polymeric gold ink BQ331 (DuPont Microcircuit Materials, Bristol, UK) as working electrode on screen printed strips, the electrochemical procedure was studied. Due to the wealth of research on electrochemical and non electrochemical methods for arsenic determination, this project attempts to capitalise on the unique advantages of the screen-printed gold surface. In particular, the issues surrounding the performance of the sensor were evaluated by electrochemical and spectroscopic means (including infrared, nuclear magnetic resonance and X-ray photoelectron spectroscopy). A number of custom screen printed electrodes were prepared in house comparing sensor performance on compositional factors. An interference coming from silver interaction with chloride in the reference electrode was identified. As such, the design of the sensor needs to change to include either an immobilising layer, such as Nafion, over the silver, or to omit screen-printed silver altogether. The Nafion was presumed to work by excluding (or at least much reducing) the passage of negatively charged chloride ions to the silver surface preventing formation of soluble silver chloride complexes. The design of the sensor was considered in light of performance and sensitivity. The screen-printed electrodes were cut to facilitate a microband design lending favourable diffusive to capacitive current characteristics. With this design, As(III) detection was demonstrated comfortably at 5 ppb (in a copper tolerant 4 M HCl electrolyte) without electrode need for additional preparation procedures. This is below the World Health Organisation (WHO) guideline and United States Environmental Protection Agency (USEPA) regulation level of 10 ppb in drinking water. The electrode materials are already mass manufacturable at an estimated cost less than £ 0.5 per electrode. Themicroband design could, in principle, be applied to mercury and other metal ions. The procedure for As(V) either with chemical or electrochemical reduction and determination still needs to be assessed. However, the presented electrode system offers a viable alternative to the colorimetric test kits presently employed around the world for arsenic in drinking water. Also, the Nicholson Method (Nicholson, 1965a), used for characterising electron transfer kinetics at electrode surfaces, was extended for application to rough surfaces using a fractal parameter introduced by Nyikos and Pajkossy (1988). This work includes mathematical derivation and numerical evaluation and gives a number of predictions for electrochemical behaviour. These predictions could not be tested experimentally, as yet, since the physical conditions must be carefully controlled.

This thesis is based on extensive experimental work over a three year Ph.D. studentship program sponsored by the AWE on laser induced breakdown spectroscopy (LIBS) for elemental analysis in the water environment. An exhaustive up-to-date literature review has revealed widely different results on the dependence of some of the LIBS parameters on both laser and target parameters. In this research, parametric measurements of the laser-water interaction events were undertaken to validate some quoted values and to attempt to resolve discrepancies within the published results. Analysis of dielectric breakdown in water bulk by focussed laser beam has shown that the threshold laser pulse energy for this was approximately 60% lower in tap water than in distilled water due to impurity content of the former. However, the effect of analyte concentration was found to be much less drastic, giving only a 10% reduction for 2 orders of magnitude of concentration increase of dissolved sodium. Parameters of cavitation bubbles, resulting from the laser induced breakdown process in the water bulk, were measured using two different techniques i.e. probe beam deflection (PBD) and high speed imaging (HSI). Values of bubble diameter before collapse (maximum) and the frequency of the oscillation were found to be different, by 27% for the diameter and by 22% for the frequency, in the results obtained using the two different techniques. The values of the parameters obtained in this study and those found in the literature vary widely and do not show any trend on their dependence with laser pulse energy. It is concluded that large uncertainty in the estimation or control of sampled volume defined by the waist of the laser beam focus render large errors on such measurements. The present work includes parametric measurement of signal-to-noise ratio (S/N) for the detection of signals from analytes dissolved in water for different variable experimental parameters. Optimum values for achieving maximum S/N were obtained. In addition to the spectral and temporal filtering for improving S/N, mechanical filtering techniques were also investigated. This has resulted in the improvement of S/N by more than 25%. The thesis concludes with remarks, based on the analysis of the experimental data, on work for further improvement of sensitivity of the LIBS technique and its wider application as a portable device for in situ, real time point monitoring of elemental contaminants in water.

This thesis presents an. investigation of the feasibility of exploiting the pulsed indirect photoacoustic spectroscopy (pIPAS) with respect to the remote detection and identification of hazardous liquid chemical species at ranges up to 10m. 2 / Modelling of the pulsed photoacoustic generation mechanism relevant to the case of its generation by pulsed laser irradiation of liquid samples at locations remote from the laser source and acoustic detection equipment was conducted to provide insight into the efficiency of the photoacoustic mechanism and the principle factors which determine the photoacoustic signal magnitude. The peak-to-peak pressure of the photoacoustic signal has been shown to be l.inearly dependent on the absorption coefficient of the sample and the laser pulse energy, and to vary inversely with the distance from the sampie to the detector. The duration of the photoacoustic signal is also dependent on a temporal characteristic which is defmed in terms of a combination of the laser pulse ,.-/ length and microphone impulse response. To demonstrate the feasibility of this method as a remote technique implemented outside the confmes of a photoacoustic cell, it has been necessary to produce a significant enhancement in the photoacoustic signal magnitude over that demonstrated in preliminary 'short range' laboratory experiments. Modifications to the experimental system design were observed to produce an increase in the photoacoustic signal by a factor of -10 and the detector sensitivity by a factor of -30, which together were sufficient to allow the laser-generated acoustic signal to be measurable over ranges of several metres. Using a pulsed C02 laser, tunable from 9.2 - 1O.9J.lm, the photoacoustic spectrum of simulant hazardous liquid chemicals has been measured at ranges up to 8m in the laboratory. Excellent agreement was obtained between the photoacoustic spectrum obtained using the PIPAS technique and the spectrum measured using a conventional transmission spectrometer. Using these system enhancements, positive identification of simulant liquids and unambiguous discrimination between the spectrum of typical background materials and simulant hazardous liquids has been demonstrated repeatedly and reliably.