Browsing by Author "Walton, Christopher"
Now showing 1 - 19 of 19
Results Per Page
Sort Options
Item Open Access Aircraft Cabin Air Sampling Study: Part 1 of the Final Report(2011-03) Crump, Derrick; Harrison, Paul; Walton, ChristopherThis report describes the methodology and results of a study of aircraft cabin air quality undertaken by Cranfield University and two contracted analytical laboratories on behalf of the Department for Transport (DfT). The project began in 2007 and was carried out under the leadership of the late Helen Muir OBE (Professor of Aerospace Psychology, Cranfield University) until her illness and untimely death in the first quarter of 2010. The authors and project team are indebted to Helen for her inspiring contribution that made this project and our report possible. She is sadly missed.Item Open Access Aircraft Cabin Air Sampling Study; Part 2 of the Final Report(2011-04) Crump, Derrick; Harrison, Paul; Walton, ChristopherThis is the second part of the report on aircraft cabin air quality prepared by Cranfield University for the Department for Transport. The study was set up in light of concerns about possible adverse impacts on the health and well-being of air crew resulting from exposure to substances in cabin air. Part 1 of the report describes in detail the methodology used in the study, summarises the results obtained and assesses cabin air quality against available exposure limits and the quality of air encountered in domestic settings. This second part comprises principally a record of the data obtained on individual flight sectors.Item Open Access Analysis of volatile organic compounds in breath as a potential diagnostic modality in disease monitoring(Cranfield University, 2011-12) Patel, Mitesh Kantilal; Walton, ChristopherThe use of breath odours in medical diagnosis dates back to classical times, though in its modern form the technique is only a few decades old. There are several breath tests in common clinical use, though all of them involve administration of a known or labelled exogenous compound. More recently, over the last twenty years, interest has focussed on analysis of endogenous metabolites in breath, but despite a large number of published studies reporting a number of disease markers, there has been little or no impact on clinical practice. Nonetheless, breath analysis offers a number of potential advantages over current biochemical methods. One major advantage of breath analysis is its non-invasive nature, which has led to significant interest in its use at point-of care for monitoring chronic diseases such as diabetes and the chronic infections ubiquitous in cystic fibrosis. However, breath analysis classically involves the use of expensive laboratory based analytical equipment which requires extensively-trained personnel and which cannot readily be miniaturised. Systems based on simple gas sensors might offer a way of overcoming these limitations. In recent years, Cranfield University has developed an instrument called the single metal oxide sensor gas analyser (SMOS-GA, more commonly referred to as the “Breathotron”) as a proof of concept for sensor-based breath analysis. In this project the Breathotron has been used in conjunction with selected ion flow tube mass spectrometry (SIFT-MS) and thermal desorption gas chromatography mass spectrometry (TD-GC-MS) to determine the changes in the concentrations of volatile organic compounds (VOCs) in breath in a number of experimental situations which a relevant to the diagnostic monitoring of diabetes mellitus. Studies conducted on clinically healthy volunteers were: an oral glucose tolerance test (OGTT); a six minute treadmill walking test; and a bicycle ergometer test. Additionally Breathotron and analytical data were also obtained during a hypoglycaemic clamp study carried out on hypoglycaemia-unaware Type I diabetics. The principle breath volatiles determined analytically were: acetone, acetaldehyde, ammonia isoprene though data on a number of others was also available. In general, it proved difficult to establish any reproducible relationship between the concentration of any compound measured and blood glucose concentration any of the experimental interventions. It was notable, though, that statistically significant associations were observed occasionally in data from individual volunteers, but even these were not reproduced in those trials which involved repeated measurements. This remained true even where spirometry data were used to derive VOC clearance rates. This may explain previous reports from smaller studies of an association between glucose and breath acetone concentration. It seems probable that any experimentally-induced changes in breath VOC concentration or clearance were of much smaller magnitude than background variability and was consequently not detectable. These observations were mirrored in the sensor-derived results. Multivariate analysis across all trials where Breathotron data were obtained suggested clustering by individual volunteer rather than glycaemic status. This suggests that that there exists a “background” breath volatile composition, dependent perhaps on such factors as long-term diet, which is independent of our experimental intervention. The Breathotron was also used as a platform to assess the performance of three different types of mixed metal oxide sensor in vitro. Calibration curves were generated for acetone, ammonia and propanol covering the physiological range of concentrations and with a similar water content to breath. Close correlations were obtained between concentration and the amplitude of the sensor response. Sensor response reproducibility was also determined using acetone at a concentration of 10ppm with dry and humidified test gas. There were significant differences between sensor types in overall reproducibility and in response to humidity. These results suggest that had there been substantial changes in breath VOC composition as a result of our experimental interventions, any of the types of sensor used would have been capable of responding to them. In summary, these results do not support the efficacy of breath VOC analysis as a means of non-invasive diagnostic monitoring.Item Open Access Analysis of volatile organic compounds of bacterial origin in chronic gastrointestinal diseases(Wiley, 2013-07-17) Walton, Christopher; Fowler, Dawn P.; Turner, Claire; Jia, W.; Whitehead, Rebekah N.; Griffiths, Lesley; Dawson, Claire; Waring, Rosemary H.; Ramsden, David B.; Cole, Jeffrey A.; Cauchi, Michael; Bessant, Conrad M.; Hunter, John O.BACKGROUND: The aim of this study was to determine whether volatile organic compounds (VOCs) present in the headspace of feces could be used to diagnose or distinguish between chronic diseases of the gastrointestinal tract and apparently healthy volunteers. METHODS: A total of 87 people were recruited, divided between 4 categories: healthy volunteers (n = 19), Crohn's disease (n = 22), ulcerative colitis (n = 20), and irritable bowel syndrome (n = 26). They each supplied fecal samples before, and except for the healthy volunteers, after treatment. Fecal samples were incubated in a sample bag with added purified air at 40°C and headspace samples were taken and concentrated on thermal sorption tubes. Gas chromatography-mass spectrometry then desorbed and analyzed these. The concentrations of a selection of high-abundance compounds were determined and assessed for differences in concentration between the groups. RESULTS: Crohn's disease samples showed significant elevations in the concentrations of ester and alcohol derivates of short-chain fatty acids and indole compared with the other groups; indole and phenol were elevated in ulcerative colitis and irritable bowel syndrome but not at a statistically significant level. After treatment, the levels of many of the VOCs were significantly reduced and were more similar to those concentrations in healthy controls. CONCLUSIONS: The abundance of a number of VOCs in feces differs markedly between Crohn's disease and other gastrointestinal conditions. Following treatment, the VOC profile is altered to more closely resemble that of healthy volunteers.Item Open Access Assessment of occupational exposure to gasoline vapour at petrol stations(Cranfield University, 2016-01) Alyami, Ahmed Rashid; Crump, Derrick; Walton, Christopher; Magan, Naresh; Salama, KhaledPetrol station attendants’ exposure to gasoline vapours while refuelling vehicles has raised health concerns, especially in tropical countries like Saudi Arabia. This is due to the increase of gasoline vaporisation by the high temperatures and related weather conditions. This represents an increase risk of inhaling more vapours than its counterpart temperate countries. Furthermore, exposure during extended working hours (12 hrs shifts), with no vapour recovery system and the handling of gasoline containing a high percentage of volumes of toxic substances (e.g. BTEXs) have not been adequately addressed previously in Saudi Arabia. Therefore, this study was designed and carried out to investigate the validity of this concern by assessing and quantifying full shift exposures to gasoline vapours during the petrol filling process. Different exposure assessment methodologies were employed and evaluated for their suitability. The study assessed the exposures of 41 attendants via passive, active, and direct reading methods at twelve petrol stations with both high and low sales in the Eastern Province of Saudi Arabia. The study was conducted during the winter and summer months to test the seasonal variation of the pattern of exposure. The effects of the quantity of gasoline sold, the locations of the stations, weather variations (e.g. wind speed, temperature, and humidity) were tested. A purpose built mini-weather stations and modified thermometres were utilized to accurately monitor the prevailing weather conditions. Forward-looking infrared (FLIR) thermal image cameras were utilised to visualise the size and movement behaviour of the vapour plumes during petrol refuelling. Furthermore, analytical lab trials were carried out to characterise the gasoline vapour component under different temperatures. These were used to propose a new OEL. The geometric means of the personal passive results for BTEX and MTBE (0.18 ppm, 0.24 ppm, 0.09 ppm, 0.18 ppm, 1.57 ppm, respectively) were found to be relatively higher than those reported previously for Europe and North America. These results are discussed in the context of the impact that such exposure will have on people involved in this industry in petrol stations in Saudi Arabia.Item Open Access Breath acetone concentration decreases with blood glucose concentration in type I diabetes mellitus patients during hypoglycaemic clamps(IOP Publishing, 2009-12-02T00:00:00Z) Turner, Claire; Walton, Christopher; Hoashi, Shu; Evans, MarkConventional wisdom is that breath acetone may be markedly elevated in type 1 diabetes, but that this only occurs during poor blood glucose control and/or intercurrent illness. In contrast, little is known about breath acetone at more representative everyday blood glucose levels in diabetes. We used selected ion flow tube mass spectrometry to monitor the breath of eight patients with type 1 diabetes mellitus during 'insulin clamp' studies in which insulin and glucose were infused into patients to lower blood glucose levels in steps from normal values into the low glucose (hypoglycaemic) range. The concentration of acetone in breath and the blood sugar concentration of the patients were monitored at each blood glucose concentration. The blood glucose level at the start of the study was typically about 6 mM L-1, whereas the breath acetone concentration at this blood glucose level was unexpectedly variable, ranging from 1 part-per- million to 21 ppm, in contrast to what was previously believed, i.e. that type 1 diabetes mellitus is characterized by high acetone levels. In all eight patients, the breath acetone declined linearly with blood glucose concentration.Item Open Access Cabin Air Sampling Study Functionality Test.(Cranfield University School of Engineering, 2008-01) Muir, Helen; Walton, Christopher; McKeown, RebeccaThe Department for Transport (DFT), on behalf of the Government’s Aviation Health Working Group (AHWG), commissioned Cranfield University to organise, manage and deliver a functionality test of a variety of air sampling devices capable of detecting a wide range of compounds in a cabin air environment. The functionality test was to be the preliminary stage of a major monitoring study of the cabin air environment, which the Department intends to conduct.Item Open Access Diversity and distribution of sulphate-reducing bacteria in human faeces from healthy subjects and patients with inflammatory bowel disease(2012-06-01T00:00:00Z) Jia, Wenjing; Whitehead, Rebekah N.; Griffiths, Lesley; Dawson, Claire; Bai, Hao; Waring, Rosemary H.; Ramsden, David B.; Hunter, John O.; Cauchi, Michael; Bessant, Conrad M.; Fowler, Dawn P.; Walton, Christopher; Turner, Claire; Cole, Jeffrey A.The relative abundance of different groups of sulphate-reducing bacteria (SRB) in faecal DNA collected before and after therapy from patients suffering from Crohn's disease (CD), irritable bowel syndrome (IBS) or ulcerative colitis (UC) has been compared with that from healthy controls. Growth tests revealed that SRB were not more abundant in samples from patients with CD before treatment than in the healthy control group. For most of the 128 samples available, these preliminary results were confirmed using degenerate PCR primers that amplify the dsrAB gene. However, some samples from patients with CD before treatment contained a growth inhibitor that was absent from IBS or UC samples. In-depth sequencing of PCR-generated dsrB fragments revealed that the diversity detected was surprisingly low, with only eight strains of SRB and the sulphite-reducing bacterium, Bilophila wadsworthia, detected above the 0.1% threshold. The proportion of the two major species detected, B.wadsworthia and Desulfovibrio piger, was as high as 93.5% of the total SRB population in the healthy control group and lower in all patient groups. Four previously undescribed species were found: it is impossible to predict whether they are sulphate or sulphite-reducing bacteria.Item Open Access Enteral feeding reduces metabolic activity of the intestinal microbiome in Crohn’s disease: an observational study(Nature Publishing Group, 2016-05-11) Walton, Christopher; Montoya, M. P. B.; Fowler, Dawn P.; Turner, Claire; Jia, W.; Whitehead, Rebekah N.; Griffiths, Lesley; Waring, Rosemary H.; Ramsden, David B.; Cole, Jeffrey A.; Cauchi, Michael; Bessant, Conrad M.; Naylor, J.; Hunter, John O.BACKGROUND/OBJECTIVES: Enteral feeding will induce remission in as many as 80–90% of compliant patients with active Crohn’s disease (CD), but its method of action remains uncertain. This study was designed to examine its effects on the colonic microbiome. METHODS/SUBJECTS: Healthy volunteers and patients with CD followed a regimen confined to enteral feeds alone for 1 or 2 weeks, respectively. Chemicals excreted on breath or in faeces were characterised at the start and at the end of the feeding period by gas chromatography/mass spectrometry. RESULTS: One week of feeding in healthy volunteers caused significant changes in stool colour and deterioration in breath odour, together with increased excretion of phenol and indoles on the breath. Feeding for 2 weeks in patients with CD produced significant improvements in symptoms and a decrease in the concentration of C-reactive protein. The faecal concentrations of microbial products, including short-chain fatty acids (SCFAs), and potentially toxic substances, including 1-propanol, 1-butanol and the methyl and ethyl esters of SCFAs, showed significant falls. CONCLUSIONS: A significant change occurs in the production of microbial metabolites after enteral feeding in both healthy volunteers and patients with CD. Many of those detected in CD are toxic and may feasibly lead to the immunological attack on the gut microbiota, which is characteristic of inflammatory bowel disease. The reduction in the production of such metabolites after enteral feeding may be the reason for its effectiveness in CD.Item Open Access An exploratory comparative study of volatile compounds in exhaled breath and emitted by skin using selected ion flow tube mass spectrometry(John Wiley & Sons, Ltd, 2008-01-01T00:00:00Z) Turner, Claire; Parekh, Bhavin; Walton, Christopher; Španěl, Patrik; Smith, David; Evans, MarkThis study examined the utilization patterns of key Carbon sources (CS, 24: including key sugars, aminoacids and fatty acids) in maize by strains of Aspergillus flavus and Fusarium verticillioides under different water activity (aw, 0.87-0.98 aw) and temperature (20-35°C) values and compared the niche overlap indices (NOI) that estimate the in vitro carbon source utilization profiles (Wilson and Lindow, 1994). The ability to grow in these key CS in minimal media was studied for 120 hrs in 12 hr steps. The NOI was calculated for inter-species (F. verticillioides – A. flavus) and for intra-species (A. flavus - A. flavus) using CS utilisation patterns over the range of interacting environmental conditions. 30°C, over the whole aw range examined, was found to be optimal for utilization of the maximum number of CS by A. flavus. In contrast, for F. verticillioides this was more so at 20°C; 25°C allowed a suboptimal usage of CS for both species. NOIs confirmed the nutritional dominance of A. flavus at 30°C, especially at lower aw levels and that of F. verticillioides at 20°C, mainly at 0.95 aw. In other conditions of aw, based on CS utilization patterns, the data indicated that A. flavus and F. verticillioides occupied different ecological niches. The variability in nutritional sources utilization between A. flavus strains was not related to their ability to produce aflatoxins (AFs). This type of data helps to explain the nutritional dominance of fungal species and strains under different environmental conditions. This could be useful in trying to find appropriate natural biocontrol microorganisms to compete with these mycotoxigenicItem Open Access Exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) at Nigeria's petrol stations: a review of current status, challenges and future directions(Frontiers, 2024-03-25) Anigilaje, Emmanuel Ademola; Nasir, Zaheer Ahmad; Walton, ChristopherIntroduction: In Nigeria, because of increasing population, urbanization, industrialization, and auto-mobilization, petrol is the most everyday non-edible commodity, and it is the leading petroleum product traded at the proliferating Nigeria's petrol stations (NPSs). However, because of inadequate occupational health and safety (OHS) regulatory measures, working at NPSs exposes petrol station workers (PSWs) to a large amount of hazardous benzene, toluene, ethylbenzene, and xylene (BTEX) compounds. Methods: Studies on BTEX exposures among Nigerian PSWs are scarce. Thus, constraints in quantifying the health risks of BTEX limit stakeholders' ability to design practical risk assessment and risk control strategies. This paper reviews studies on the OHS of Nigerian PSWs at the NPSs. Results: Although knowledge, attitude, and practices on OHS in NPSs vary from one Nigeria's study setting to another, generally, safety practices, awareness about hazards and personal protective equipment (PPE), and the use of PPE among PSWs fell below expectations. Additionally, air quality at NPSs was poor, with a high content of BTEX and levels of carbon monoxide, hydrogen sulfide, particulate matter, and formaldehyde higher than the World Health Organization guideline limits. Discussion: Currently, regulatory bodies' effectiveness and accountability in safeguarding OHS at NPSs leave much to be desired. Understanding the OHS of NPSs would inform future initiatives, policies, and regulations that would promote the health and safety of workers at NPSs. However, further studies need to be conducted to describe the vulnerability of PSWs and other Nigerians who are occupationally exposed to BTEX pollution. More importantly, controlling air pollution from hazardous air pollutants like BTEX is an essential component of OHS and integral to attaining the Sustainable Development Goals (SDG) 3, 7, and 11.Item Open Access Faecal volatile biomarkers of Clostridium difficile infection(PLOS (Public Library of Science), 2019-04-15) Patel, Mitesh; Fowler, Dawn; Sizer, Jeremy; Walton, ChristopherCare of patients with potential CDI can involve isolation and use of antibiotics, often before a definitive diagnosis is available, impacting healthcare resource and contributing to antibiotic resistance. There is anecdotal evidence that the faeces of CDI patients have a distinctive odour, while it is well-established that changes in the gut microbiota are associated with changes in the volatile organic compounds (VOC) produced. A total of twenty-four candidate volatile biomarkers were identified from a review of the literature including in vitro, animal and human studies. Using thermal desorption-gas chromatography-time-of flight mass spectrometry (TD-GC-ToFMS), VOC emission rates were determined on stored frozen stool samples from 53 CDI-positive and 53 CDI-negative patients with unexplained diarrhoea which had previously been diagnosed using enzymatic and nucleic acid amplification tests. Sample preparation was limited to placement of a subsample in an appropriate container. Compounds exhibiting a statistically significant difference (p < 0.05) in emission rate between the CDI-positive and–negative groups and a corresponding area under the receiver-operator characteristic curve (ROC) >0.7 were considered potentially indicative of CDI. Seven compounds were so identified: propan-1-ol (ROC 0.75), 3-methylbutanal (ROC 0.84), ethyl propionate (ROC 0.81), hexanoic acid (ROC 0.73), 4-methylphenol (ROC 0.81), dodecane (ROC 0.80) and indole (ROC 0.85). A number of potential volatile biomarkers of CDI can be sampled rapidly and with little prior preparation from faecal samples of patients with diarrhoea. Of these 4-methylphenol (p-cresol) is of particular interest as it has been anecdotally linked to CDI and is closely related to the biology and virulence of Clostridium difficile. This approach shows promise for the rapid, point-of-care diagnosis of CDI with good sensitivity and specificity.Item Open Access Instrumentation for quantitative analysis of volatile compounds emission at elevated temperatures. Part 1: Design and implementation(Nature Publishing Group, 2020-05-26) Lourenço, Célia; Bergin, Sarah; Hodgkinson, Jane; Francis, Daniel; Staines, Stephen E.; Saffell, John R.; Walton, Christopher; Tatam, Ralph P.A novel suite of instrumentation for the characterisation of materials held inside an air-tight tube furnace operated up to 250 °C has been developed. Real-time detection of released gases (volatile organic compounds (VOCs), CO2, NO, NO2, SO2, CO and O2) was achieved combining commercial off-the-shelf (COTS) gas sensors and sorbent tubes for further qualitative and semi-quantitative analysis by gas chromatography-mass spectrometry coupled to thermal desorption (TD-GC-MS). The test system was designed to provide a controlled flow (1000 cm3 min−1) of hydrocarbon free air through the furnace. The furnace temperature ramp was set at a rate of 5 °C min−1 with 10 min dwell points at 70 °C, 150 °C, 200 °C and 250 °C to allow time for stabilisation and further headspace sampling onto sorbent tubes. Experimental design of the instrumentation is described here and an example data set upon exposure to a gas sample is presented.Item Open Access Instrumentation for quantitative analysis of volatile compounds emission at elevated temperatures. Part 1: Design and implementation(Cranfield University, 2020-05-27 20:00) Lourenco, Celia; Bergin, Sarah; Hodgkinson, Jane; Francis, Daniel; Staines, Stephen E.; Saffell, John R.; Walton, Christopher; Tatam, RalphData to support manuscript Part 1.Item Unknown Instrumentation for quantitative analysis of volatile compounds emission at elevated temperatures. Part 2: Analysis of carbon fibre reinforced epoxy composite(Cranfield University, 2020-05-27 20:01) Lourenco, Celia; Francis, Daniel; Fowler, Dawn; E. Staines, Stephen; Hodgkinson, Jane; Walton, Christopher; Bergin, Sarah; Tatam, RalphData to support manuscript Part 2.Item Unknown Instrumentation for quantitative analysis of volatile compounds emission at elevated temperatures. Part 2: Analysis of carbon fibre reinforced epoxy composite(Nature Publishing Group, 2020-05-26) Lourenço, Cecilia; Bergin, Sarah; Hodgkinson, Jane; Francis, Daniel; Staines, Stephen E.; Saffell, John R.; Walton, Christopher; Tatam, Ralph P.We have investigated the release of gases and volatile organic compounds (VOCs) from a carbon fibre reinforced epoxy composite matrix used in aircraft structural components. Analysis was performed at several temperatures both up to and above the recommended operating temperature (121 °C) for the material, to a maximum of 250 °C. Gas chromatography-mass spectrometry (GC-MS) combined with thermal desorption (TD-GC-MS) was used to identify and quantify VOCs, and in parallel real-time gas detection with commercial off-the-shelf (COTS) gas sensors. Under hydrocarbon free air, CO, SO2, NO, NO2 and VOCs (mainly aldehydes, ketones and a carboxylic acid) were detected as the gaseous products released during the thermal exposure of the material up to 250 °C, accompanied by increased relative humidity (4%). At temperatures up to 150 °C, gas and volatile emission was limited.Item Unknown Mid-IR spectroscopic instrumentation for point-of-care diagnosis using a hollow silica waveguide gas cell(International Society for Optics and Photonics - SPIE, 2017-02-17) Francis, Daniel; Hodgkinson, Jane; Walton, Christopher; Sizer, Jeremy; Black, Paul; Livingstone, Beth; Fowler, Dawn P.; Patel, Mitesh K.; Tatam, Ralph P.Laser spectroscopy provides the basis of instrumentation developed for the diagnosis of infectious disease, via quantification of organic biomarkers that are produced by associated bacteria. The technology is centred on a multichannel pulsed quantum cascade laser system that allows multiple lasers with different wavelengths to be used simultaneously, each selected to monitor a different diagnostic biomarker. The instrument also utilizes a hollow silica waveguide (HSW) gas cell which has a very high ratio of interaction pathlength to internal volume. This allows sensitive detection of low volume gas species from small volume biological samples. The spectroscopic performance of a range of HSW gas cells with different lengths and bore diameters has been assessed using methane as a test gas and a best-case limit of detection of 0.26 ppm was determined. The response time of this cell was measured as a 1,000 sccm flow of methane passed through it and was found to be 0.75 s. These results are compared with those obtained using a multi-pass Herriot cell. A prototype instrument has been built and approved for clinical trials for detection of lung infection in acute-care patients via analysis of ventilator breath. Demonstration of the instrument for headspace gas analysis is made by monitoring the methane emission from bovine faeces. The manufacture of a hospital-ready device for monitoring biomarkers of infection in the exhaled breath of intensive care ventilator patients is also presented.Item Unknown Quantification of liquid phase faecal odourants to evaluate membrane technology for wastewater reuse from decentralised sanitation facilities(Royal Society of Chemistry, 2018-11-29) Mercer, Edwina V.; Davey, Christopher J.; Campo Moreno, Pablo; Fowler, Dawn; Williams, Leon; Kolios, Athanasios; Parker, Alison; Tyrrel, Sean; Walton, Christopher; Cartmell, Elise; Pidou, Marc; McAdam, Ewan J.Public willingness to use decentralised sanitation facilities or arising water products is discouraged due to malodour, preventing improved sanitation practices or water reuse opportunities in low income countries Whilst odour is characterised in the gas phase, it originates in the liquid phase. Consequently, controlling odour at source could prevent gas-phase partitioning and limit produced water contamination. This study therefore developed an analytical method for the quantitation of a range of liquid phase volatile organic compounds (VOCs) classified into eight chemical groups, known to be primary indicators of faecal odour, to provide characterisation of real fluids and to permit evaluation of several potential membrane separation technologies for liquid phase odourant separation. The gas chromatography mass spectrometry method provided quantitation in the range of 0.005 mg L-1 to 100 mg L-1 with instrument detection limits ranging from 0.005 mg L-1 to 0.124 mg L-1. Linear calibration curves were achieved (r2 >0.99) with acceptable accuracy (77-115%) and precision (<15%) for quantitation in the calibration range below 1 mg L 1, and good accuracy (98-104%) and precision (<2%) determined for calibration in the range 1-100 mg L-1. Pre-concentration of real samples was facilitated via solid phase extraction. Subsequent application of the method to the evaluation of two thermally driven membranes based on hydrophilic (polyvinyl alcohol) and hydrophobic (polydimethylsiloxane) polymers evidenced contrasting separation profiles. Importantly, this study demonstrates the methods utility for liquid phase VOC determination which is of use to a range of disciplines, including healthcare professionals, taste and odour specialists and public health engineers.Item Unknown Understanding the fate and transport of petroleum hydrocarbons from coal tar within gasholders(Elsevier Science B.V., Amsterdam., 2009-02-28T00:00:00Z) Coulon, Frederic; Orsi, R.; Turner, Claire; Walton, Christopher; Daly, Paddy; Pollard, Simon J. T.Coal tars have been identified as posing a threat to human health due to their toxic, mutagenic and carcinogenic characteristics. Workers involved in former gasholders decommissioning are potentially exposed to relevant concentrations of volatile and semi-volatile hydrocarbons upon opening up derelict tanks and during tar excavation/removal. While information on contaminated sites air- quality and its implications on medium-long term exposure is available, acute exposure issues associated with the execution of critical tasks are less understood. Calculations indicated that the concentration of a given contaminant in the gasholder vapour phase only depends on the coal tar composition, being only barely affected by the presence of water in the gasholder and the tar volume/void space ratio. Fugacity modelling suggested that risk-critical compounds such as benzene, naphthalene and other monocyclic and polycyclic aromatic hydrocarbons may gather in the gasholder air phase at significant concentrations. Gasholder emissions were measured on-site and compared with the workplace exposure limits (WELs) currently in use in UK. While levels for most of the toxic compounds were far lower than WELs, benzene air-concentrations where found to be above the accepted threshold. In addition due to the long exposure periods involved in gasholder decommissioning and the significant contribution given by naphthalene to the total coal tar vapour concentration, the adoption of a WEL for naphthalene may need to be considered to support operators in preventing human health risk at the workplace. The Level I fugacity approach used in this study demonstrated its suitability for applications to sealed environments such as gasholders and its further refining could provide a useful tool for land remediation risk assessors. (C) 2008 Elsevier Ltd. All rights reserved.