Victor Bocos-Bintintan

The trapped human experiment

This experiment observed the evolution of metabolite plumes from a human trapped in a simulation of a collapsed building. Ten participants took it in turns over five days to lie in a simulation of a collapsed building and eight of them completed the 6 h protocol while their breath, sweat and skin metabolites were passed through a simulation of a collapsed glass-clad reinforced-concrete building. Safety, welfare and environmental parameters were monitored continuously, and active adsorbent sampling for thermal desorption GC-MS, on-line and embedded CO, CO(2) and O(2) monitoring, aspirating ion mobility spectrometry with integrated semiconductor gas sensors, direct injection GC-ion mobility spectrometry, active sampling thermal desorption GC-differential mobility spectrometry and a prototype remote early detection system for survivor location were used to monitor the evolution of the metabolite plumes that were generated. Oxygen levels within the void simulator were allowed to fall no lower than 19.1% (v). Concurrent levels of carbon dioxide built up to an average level of 1.6% (v) in the breathing zone of the participants. Temperature, humidity, carbon dioxide levels and the physiological measurements were consistent with a reproducible methodology that enabled the metabolite plumes to be sampled and characterized from the different parts of the experiment. Welfare and safety data were satisfactory with pulse rates, blood pressures and oxygenation, all within levels consistent with healthy adults. Up to 12 in-test welfare assessments per participant and a six-week follow-up Stanford Acute Stress Response Questionnaire indicated that the researchers and participants did not experience any adverse effects from their involvement in the study. Preliminary observations confirmed that CO(2), NH(3) and acetone were effective markers for trapped humans, although interactions with water absorbed in building debris needed further study. An unexpected observation from the NH(3) channel was the suppression of NH(3) during those periods when the participants slept, and this will be the subject of further study, as will be the detailed analysis of the casualty detection data obtained from the seven instruments used.

The response of a membrane inlet ion mobility spectrometer to chlorine and the effect of water contamination of the drying media on ion mobility spectrometric responses to chlorine

The negative mode response of a membrane inlet ion mobility spectrometer, interfaced to an Extrel-C150 mass spectrometer, to chlorine in dry air over the range of concentrations 0–200 mg m−3 was characterised. Three distinct product ions were observed: an assembly of [Cl2(H2O)n]− and [Cl(H2O)n]− entities with a reduced mobility of 2.19 cm2 V−1 s−1, a carbon dioxide based cluster, [Cl2(CO2)(H2O)3]− with a reduced mobility of 1.93 cm2 V−1 s−1 and a dimer product thought to be [(Cl2)2(H2O)]− with a reduced mobility of 1.70 cm2 V−1 s−1. The response to chlorine was found to be sensitive with a limit of detection significantly less than 1 mg m−3. Further exposures to chlorine were also undertaken with 5 and 10% by mass of water added to the adsorbent traps used to purify the drift and source gases within the instrument. This was done to simulate ageing of the air purification media. No changes in the chemistry of the product ions were observed with increasing levels of water contamination of the adsorbent media. The sensitivity was reduced and the observed drift times increased with increasing levels of water contamination with the reduced mobilities for the three product ion groups above found to vary across the ranges: 2.10–2.19, 1.84–1.93 and 1.66–1.70 cm2 V−1 s−1, respectively.

Characterisation of the phosgene response of a membrane inlet 63Ni ion mobility spectrometer

A membrane inlet 63Ni ion mobility spectrometer interfaced to a quadrupole mass spectrometer with permeation, exponential dilution approaches and syringe-based systems were used to characterise the ion mobility spectrometry (IMS) response to phosgene in dry air (water concentration less than 16.5 mg m(-3)). Phosgene produced a principle product ion in the negative mode with a reduced mobility of 2.16 cm2 V(-1) s(-1), with an unresolved artefact at higher concentrations having a reduced mobility of 2.32 cm2 V(-1) s(-1). The limit of detection of the system with a membrane inlet fitted was estimated to be less than 1 mg m(-3), with an upper limit to the dynamic range of 32 mg m(-3). Mass spectrometric data indicated the existence of [(H2O)nCl]-, [(H2O)nCl2]-; [(H2O)n(O2)Cl]-; [(H2O)n(O)Cl]-; and, [(H2O)n(CO2)Cl]-. The existence of two possible mechanisms for product ion formation is proposed: dissociative electron capture, as well as hydrolysis followed by electron capture. The effect of water contamination of the drying media within the ion mobility spectrometer was also investigated, and the effects were similar to those observed previously with studies on chlorine. Reduced mobility of the product ions was observed to decrease with increasing water contamination of the drying media used within the instrument, while limits of detection increased slightly to less than 2.4 mg m(-3), with no significant effect on dynamic ranges of response or resolution. Preliminary results also indicated a positive mode response for phosgene, albeit at significantly higher concentrations to those observed in the negative mode.

Mass spectrometric techniques for the analysis of volatile organic compounds emitted from bacteria

Bacteria are the main cause of many human diseases. Typical bacterial identification methods, for example culture-based, serological and genetic methods, are time-consuming, delaying the potential for an early and accurate diagnosis and the appropriate subsequent treatment. Nevertheless, there is a stringent need for in situ tests that are rapid, noninvasive and sensitive, which will greatly facilitate timely treatment of the patients. This review article presents volatile organic metabolites emitted from various micro-organism strains responsible for common bacterial infections in humans. Additionally, the manuscript shows the application of different analytical techniques for fast bacterial identification. Details of these techniques are given, which focuses on their advantages and drawbacks in using for volatile organic components analysis.

The effect of growth medium on an Escherichia coli pathway mirrored into GC/MS profiles

Escherichia coli (E. coli) is a Gram-negative coliform bacterium that is commonly found in the lower intestine of warm-blooded organisms. Most of the strains are harmless but some serotypes are pathogenic, meaning they can cause illness, either diarrhea or illness outside the intestinal tract. The aim of this work is to assess which components are generated for the purpose of E. coli target analysis. In this study, we intend to emphasize the importance of cultivability and to prove that growth media plays a crucial role in bacteria growth. To do this, E. coli was cultivated in three different growth mediums: (a) trypcase soy broth (TSB), (b) Mueller Hinton (MH), and (c) minimal salts (M9) enriched with glucose, respectively. Solid phase micro extraction was used as a sampling method, followed by gas chromatography-mass spectrometry for subsequent analysis. The relevant microbial volatile organic compounds (MVOCs) released in the headspace over the cultures of the E. coli bacteria and the afferent metabolic processes that occur in order to generate these compounds are presented in this work. The characteristic volatile compounds found in E. coli strain emissions were indole, phenylethyl alcohol and a series of esters when it was grown in TSB. Different pyrazines were found (pyrazine, 2-ethyl-3,5-dimethyl-, pyrazine, 2,5-dimethyl- and pyrazine, trimethyl-) when it was cultivated in MH. Long-chain alcohols such as 2-pentadecanol, 9-tetradecen-1-ol and 11-hexadecenol occurred in M9. Dimethyl disulfide, dimethyl trisulfide and a consistent number of alcohols and ketones were observed for E. coli cultivated in all three growth mediums. The occurrence and biosynthesis of these MVOCs clearly denote that the growth media used plays a crucial role in bacterial cultivation. The biomarker chemicals documented from this work may ultimately be used to identify bacterial infections by analyzing exhaled breath.