Browsing by Author "Setford, S."

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    Analytical methods for assessing paper degradation In transformers
    (Cranfield University, 2006-05) Christofidis, Stavros; Setford, S.; Ritchie, Laurie; Aldred, David
    Power transformers are essential equipments for distributing electricity. However, maintenance of these equipments is necessary to ensure long working life and to avoid catastrophic incidents. Insulation of the instrument is essential, and mainly consists of mineral oil and cellulosic paper. This research work investigates and examines in a series of different experiments the compounds produced from the degradation of the cellulosic paper, known as furanic compounds. Five furanic derivatives (5-HMF, 2-FAL, 2-ACF, 5-MEF and FOL) were examined, and it was established throughout this work that these furanic compounds degradate faster in aqueous solution, under a controlled environment, than in an organic, it is possible to produce from one furanic compound other derivatives, and finally each furanic compound distributes differently in an oil water environment, affecting the recovery of each individual. The knowledge obtained from this research work can be used for the development of the existing method of analysis of furanic compounds, and help to provide a better diagnosis of the insulation state of the transformer.
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    At-line testing of chlorophenol and chloroanisole contaminants in commercial wine production.
    (Cranfield University, 2004-09) Nicholls, C. R.; Saini, S.; Setford, S.
    The research described in this thesis concerns the development of at-line test procedures for the detection of trace levels of chlorophenols and chloroanisoles in wine and related materials. Competitive ELISA assays were developed and optimised for pentachlorophenol and pentachloroanisole to enable the detection of chlorophenols and chloroanisoles in the range 0.1 to 100ng/ml in purified sample extracts, using antibodies supplied by the French consortium partner, Diaclone, together with synthesised conjugate materials, based on the enzyme horseradish peroxidase. The cross reactivity of the assay towards chlorophenol and chloroanisole congeners in wine was investigated and the pentachlorophenol assay was selected as the most efficient antibody to detect and quantify both chlorophenol and chloroanisole congeners. The use of synthetic receptors based on molecularly imprinting technology was also investigated for pentachlorophenol and pentachloroanisole, and a new assay format (Displacement Imprinted Polymer Analysis (DIPRA)) was established to measure chlorophenols in contaminated materials at a concentration range of 0.1 to 50 µg/ml, based on the displacement of a reporter molecule rebound to the synthetic receptor sites. Two alternative reporter molecules were synthesised by linking a pentachlorophenol derivative (2,3,5,6-tetrachloro-4-hydroxy phenoxy acetic acid) to the enzyme horseradish peroxidase or 7-amino-4-methylcoumarin-3-acetyl hydrazide. Alternative hyphenated sample extraction and purification methods based on solid phase extraction, steam distillation and liquid/liquid partition were evaluated to enable the ELISA and DIPRA test methods to be employed using the limited facilities of a local winery laboratory. The application of the procedures to the analysis of sample types such as wine, corks and packaging materials was undertaken to investigate the suitability of the test methods for inclusion in quality control and incident analysis protocols.
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    Data analysis tools for safe drinking water production
    (Cranfield University, Cranfield University at Silsoe, 2006-11-08T17:00:01Z) Cauchi, Michael; Setford, S.; Bessant, Conrad
    Providing safe and high quality drinking water is essential for a high quality of life. However, the water resources in Europe are threatened by various sources of contamination. This has led to the development of concepts and technologies to create a basis for provision of safe and high quality drinking water, which had thus resulted in the formation of the Artificial Recharge Demonstration project (ARTDEMO). The overall aim of this thesis in relation to the ARTDEMO project was to develop a realtime automated water monitoring system, capable of using data from various complementary sources to determine the amounts of inorganic and organic pollutants. The application of multivariate calibration to differential pulse anodic stripping voltammograms and fluorescence spectra (emission and excitation-emission matrix) is presented. The quantitative determination of cadmium, lead and copper acquired on carbon-ink screen-printed electrodes, arsenic and mercury acquired on gold-ink screen-printed electrodes, in addition to the quantitative determination of anthracene, phenanthrene and naphthalene have been realised. The statistically inspired modification of partial least squares (SIMPLS) algorithm has been shown to be the better modelling tool, in terms of the root mean square error of prediction (RMSEP), in conjunction with application of data pre-treatment techniques involving rangescaling, filtering and weighting of variables. The % recoveries of cadmium, lead and copper in a certified reference material by graphite furnace atomic absorption spectrometry (GF-AAS) and multivariate calibration are in good agreement. The development of a prototype application on a personal digital assistant (PDA) device is described. At-line analysis at potential contamination sites in which an instant response is required is thus possible. This provides quantitative screening of target metal ions. The application imports the acquired voltammograms, standardises them against the laboratory-acquired voltammograms (using piecewise direct standardisation), and predicts the concentrations of the target metal ions using previously trained SIMPLS models. This work represents significant progress in the development of analytical techniques for water quality determination, in line with the ARTDEMO project's aim of maintaining a high quality of drinking water.
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    Diagnostic technologies for wound monitoring
    (Cranfield University, 2006-03) Trill, Helen; Setford, S.; Saini, S.
    Chronic wound infections represent a worldwide problem, generating high morbidity and medical expense. Failure to control infections such as MRSA in the reparative process of a wound can cause disruption of normal anatomical structure and function, resulting in a chronic wound. Existing approaches to identifying infection largely involve surveying a range of physical parameters, and a limited use of non-invasive technologies. Evaluation is time consuming, and often results in inconsistencies in patient care. This project researches three possible alternative methodologies/technologies for the monitoring of wounds, by measuring components of wound fluid. Two of the three technologies are designed to be used by physicians and patients, similarly to commercially available home blood glucose test kits, and are based on the measurement of three biomarkers: glucose, ethanol and H2O2 in PBS, and in serum as surrogate wound fluid. The first is a voltammetric technique known as dual pulse staircase voltametry (DPSV), which produces peaks characteristic of particular analytes at an electrode. The second is an amperometric biosensor array, based on screen printed three electrode assembies of carbon, rhodinised carbon (glucose biosensor only) and Ag/AgCl reference. The glucose biosensor uses glucose oxidase enzyme as the biorecognition agent, the H2O2 biosensor is a mediated system using horseradish peroxidase enzyme and dimethylferrocene mediator, and the ethanol biosensor is a bienzyme mediated system utilising alcohol oxidase enzyme horseradish peroxidase enzyme and coupled dimethylferrocene mediator. Wounds are known to produce characteristic odours, therefore the third technology studied is a single sensor odour analyser with advanced data analysis to detect five commonly occuring wound bacteria, S.aureus, K.pneumoniae, S.pyogenes, E.coli and P.aeruginosa in growth media and surrogate wound fluid. This technology would be used as a 'near patient' monitoring system and is based on machine olfaction similar to that of a commercial electronic nose, but uses a single metal oxide sensor in combination with principle components analysis. DPSV scans of the individual analytes demonstrated distinctive peaks, exhibiting nonlinear relationships with concentration. A great deal of useful information was generated using this technique, however, limitations were discovered regarding repeatability and inter-analyte interference in mixtures. Limits of detection in surrogate wound fluid with the glucose biosensor, hydrogen peroxide biosensor, and ethanol biosensor were as follows: 169.5 µM glucose, 8.43 µM hydrogen peroxide, and 7.94 µM ethanol respectively (all at 99.7% confidence). Direct detection of ethanol from metabolically active S.aureus in surrogate wound fluid yielded a limit of detection of 1.23 x 108 CFU/ml at 99.7% confidence, and 19 µM in terms of ethanol specific response. The single sensor odour analyser demonstrated the ability to detect and discriminate between the three biomarkers, between five bacteria individually, and partial discrimination of paired bacteria (in broth and surrogate wound fluid). It was also found that S.aureus could be detected down to a cell density of 5x106CFU/ml in surrogate wound fluid, lower than that found for the biosensor concept.
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    Early detection and monitoring of fuel leaks
    (2005-08) Huntley, Sharon L.; Setford, S.
    A novel integrated detection system· has been developed to protect the environment from hydrocarbon fuels leaking from large-scale storage facilities. Over the last decade, land and subsequent groundwater contamination from hydrocarbon fuels has been identified as the major threat to drinking water resources across Europe and the United States. The integrated system developed within this work has two main components: (1) 'Early warning' free-phase fuel leak detection sensors; (2) A novel immunoassay field test for rapid, in situ follow-up analysis of contaminated sites through determination of the extent of the contamination and early indication of dissolved-phase fuel migration. (1) A prototype optical reflectometric device has been developed, in conjunction with state-of the-art data acquisition and relay technology to provide a simple, low-cost hydrocarbons monitoring solution. In extensive field trials, this system has been evaluated as a multiple-array, sub-surface, remote leak detection and monitoring system for early detection of free-phase hydrocarbon contamination. The sensors respond to all. free phase hydrocarbons and can determine plume movement through soil. Preliminary leak information from these sensors can be combined with subsequent, quantitative site analysis using the immunoassay to provide an integrated, highly sensitive and low-cost solution for long term monitoring and analysis. (2) A novel ELISA has been developed for detection of the most controversial fuel oxygenate - \ methyl tert-butyl ether (MTBE), identified as the most major threat to groundwater (and consequently drinking water) resources above any other hydrocarbon contaminant. The ELISA is a classical competitive immunoassay involving free MTBE and a novel antigen consisting of an MTBE analogue covalently bound to BSA. The ELISA was optimised and transposed into a magnetic bead format, the detection range was 0.5-5000 ppm (IC50 5 ppm, assay time 65 minutes). Also detectable are MTBE degradation products TBA, TBF and alternative fuel oxygenates TAME, DIPE and ETBE. MTBE is highly soluble in water and so is an excellent marker for assessing the extent of site contamination. This integrated detection system potential provides a sensitive, cost-effective solution for early detection, analysis and surveillance of petroleum fuel contamination in a range of applications.
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    Electrochemical method for the determination of arsenic 'in the field' using screen-printed grid electrodes
    (Cranfield University, 2008-02) Dudeney, Richard; Setford, S.; Newman, Jeffrey D.; Tothill, Ibtisam E.
    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.
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    Electrochemical method for the rapid in situ screening of heavy metals in soil and water samples
    (2004-03) Cooper, Joanne; Setford, S.; Bolbot, J. A.; Saini, S.
    The aim of this work has been to develop a field-based electrochemical sensor for the detection of cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), arsenic (As) and mercury (Hg) in soil and water samples. In situ analysis, using rapid sample screening tools, can facilitate monitoring and remediation processes by minimising delays and substantially reducing costs. Disposable screen-printed electrodes (SPEs) have been fabricated using low-cost thick film technology. Carbon SPEs, coupled with anodic stripping voltammetry (ASV), provided a rapid, inexpensive in situ electrochemical screening sensor capable of simultaneously detecting Cd, Pb and Cu in soil and water samples in the microgram per liter range (pg I*1). A simplified soil extraction procedure, using 1 mol I'1 aqua regia and a three minute ultrasonic sample agitation, was developed for use with the sensor, addressing the lack of existing field-based soil extraction protocol. Extraction efficiency was evaluated using a soil certified reference material (CRM). Recoveries of 64%, 52% and 57% for Cd, Pb and Cu respectively were obtained, with a relative standard deviation (RSD) of <8% for all analytes (n=10). 82 soil samples were tested using the combined extraction + ASV sensor and compared against standard ICP-MS analysis. Correlation coefficients of 0.9782, 0.9728 and 0.9869 for Cd, Pb and Cu, respectively, indicated a good linear relationship between the two methods. A novel gold (Au) SPE, fabricated using a curable Au ink, was next evaluated for the detection of As and Hg. This is an improvement in the current state-of the-art as no surface modification or subsequent electrode adulteration to facilitate metal analyte depositioning is required. Furthermore, the Au ink can be cured at a low temperature (130°C), permitting electrode fabrication using disposable, cheap, plastic substrates. A patent has been filed. A limit of detection (LOD) of 2.7 pg I"1 and 1 pg I"1 for As3+ and Hg2+, respectively, was obtained following a 30 s depositioning. Speciation measurements for As were performed by reducing As5+ effectively over a short (10 min) reduction time using cysteine. An LOD of 42 pg f 1 following a 30 s depositioning was obtained. Initial studies also indicated the possibility of using the Au SPEs for measuring Cd, Pb and Cu, providing an alterative Hg-free procedure.
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    Extraction of genetic network from microarray data using Bayesian framework
    (2007-04) Kumuthini, Judit; Bessant, Conrad; Setford, S.
    The aim of the work described in this thesis was to develop novel methods for the extraction of gene regulatory networks (GRN) from gene expression data, and use these methods to capture previously unknown relationships between genes in specific biological applications. This has been accomplished through the application of Bayesian Networks (BN) through minimum description length (MDL) and taboo search for parameter and structure learning respectively to three large scale microarray datasets from Saccharomyeces cerevisae, Escherichia coli and human stem cells. The application of BNs for modelling the well characterised yeast cell cycle demonstrated the efficacy of the techniques employed. Using the cDNA microarray data from the yeast cell cycle project by Spellman et a l (1998), this study succeeded in extracting many biologically plausible genetic relationships, which were supported by evidence from publicly available genome and literature databases. Two novel knowledge extraction techniques were applied; Target Node (TN) analysis and learning through simulation. Further, it was demonstrated how the addition of prior knowledge to the extracted network can improve the network structure extracted purely from experimental data. The second part of this thesis demonstrated how the BN approach could be adapted to a data set of very high dimensionality, specifically data from a 54,634 probe array used to monitor human adipose tissue. Genetic networks extracted included insulin receptor (IR) and Fatty acid binding proteins (FABP) families that play key roles in fatty acid uptake, transport, and metabolism In the final part of this thesis, the genome-wide GRNs of a prokaryotic expression system were extracted from novel oligo cDNA microarray data from E-coli K12 to identify metabolic stress responsive genes during recombinant protein production. Also, detailed analysis of known metabolic stress related genes and the genes that are directly or indirectly associated in the GRN were used to establish possible markers for host system exhaustion. In conclusion, the BN methods developed proved to be a powerful and effective means of extracting GRNs in a variety of applications.
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    Field-based supercritical fluid extraction and immunoassay method for determination of organic contaminants
    (Cranfield University, 2003-05) Rigou, P; Setford, S.
    The contamination of soils, particularly by organic pollutants at industrial sites, has required the development of accurate methods of analysis to determine the nature and concentration of the pollutants, thereby allowing appropriate risk assessments and remedial strategies to be implemented. Conventional methods for site assessment generally entail extensive sampling across the whole site, with subsequent sample despatch to a centralised laboratory, where complex, solvent intensive procedures, such as Soxhlet extraction and GC-MS analyses are performed. Since such processes are laborious, expensive, and time-consuming, there has been an increasing demand for rapid and reliable field-based analytical methods for the low-cost and efficient extraction and analysis of organic pollutants from contaminated sites. This thesis describes the development of a field-compatible supercritical fluid extraction (SFE) device and method for extraction of organic contaminants from soil. SFE was chosen due to its reported high extraction efficiency, selectivity and environmentally friendly nature due to the usage of supercritical fluids as opposed to liquid solvents. A compact 72(W)xS7(D)xSO(H) cm, easily-transportable and user-friendly device was developed, based on the use of a reciprocating pump and back pressure regulator system. The optimised method yielded an average extraction recovery of 80% for total polycyclic aromatic hydrocarbons (PABs) when compared to the well-validated laboratory-based Soxhlet extraction method. Tests were performed on a range of natural samples with varying water content (0- 32% w/w) without any sample pre-treatment. In comparison, the only commercially available competing field method, based on solvent shake extraction, yielded recovery values of 20-70% coupled with poor precision. The thesis then describes the optimisation of a field applicable method for analysis of the SFE extracts, based on enzyme linked immunosorbent assays (ELISAs), a method offering speed, low cost and low solvent consumption. Available as a test kit, it was readily amenable to on-site usage requiring only simple equipment. Assay optimisation using an EPA sanctioned P AH immunoassay test kit demonstrated that the kit could function in methanolic SFE extracts diluted in buffer, hence allowing the direct analysis of total P ABs in SFE extracts with minimum sample preparation. Cross-reactivity from parent compounds was found to be an issue for the generation of quantitative data. Nevertheless, the method served as a reliable semi-quantitative technique for rapid screening of P AH levels in the SFE extracts of natural samples obtained from field-based tests. Poor performance of the solvent-shake extraction method linked to immunoassay further vindicated usage of the newly developed field-based SFEI immunoassay method. The thesis concludes by reporting on the successful field-based trials of the coupled SFE/immunoassay method. The SFE system shows promise as a valid tool for the rapid and efficient on-site monitoring of organic contaminants in soil matrices, providing an innovative and alternative approach to the commonly deployed solvent shake extraction method. The combined field-based SFElimmunoassay method is of benefit for the rapid low cost assessment of site contamination, allowing site owners and consultants alike to make rapid and informed decisions regarding site characterisation, monitoring and remediation without recourse to expensive and time consuming laboratory analyses.
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    Identification and carcinogenicity of polycyclic aromatic hydrocarbons in transformer oil.
    (Cranfield University, 2003-05) Pillai, Ilona G.; Saini, S.; Setford, S.; Heyward, R.
    Insulating oils are rich in polycyclic aromatic hydrocarbons (PAHs) which act as inhibitors of oil breakdown, but are believed to be the main source of oil mutagenicity when converted to their epoxide form by mammalian enzymes. The current industry- recognised measurement of oil risk, the IP 346 method, measures total aromatic content and therefore cannot be directly related to PAH risk. This thesis describes efforts made to establish the contribution of PAH species alone to total oil mutagenicity. Cont/d.