Abstracts of recent publications

Title: An exploratory comparative study of volatile compounds in exhaled breath and emitted by skin using selected ion flow tube mass spectrometry

Authors: Turner, C; Parekh, B; Walton, C; Spanel, P; Smith, D; Evans, M

Reference: RAPID COMMUNICATIONS IN MASS SPECTROMETRY 22526-532 Doi:1002/rcm.3402 ISSN 0951-4198 2008

Abstract: Selected ion flow tube mass spectrometry (SIFT-MS) has been used to carry out a pilot parallel study on five volunteers to determine changes occurring in several trace compounds present in exhaled breath and emitted from skin into a collection bag surrounding part of the arm, before and after ingesting 75 g of glucose in the fasting state. SIFT-MS enabled real-time quantification of ammonia, methanol, ethanol, propanol, formaldehyde, acetaldehyde, isoprene and acetone. Following glucose ingestion, blood glucose and trace compound levels were measured every 30 min for 2 h. All the above compounds, except formaldehyde, were detected at the expected levels in exhaled breath of all volunteers; all the above compounds, except isoprene, were detected in the collection bag. Ammonia, methanol and ethanol were present at lower levels in the bag than in the breath. The aldehydes were present at higher levels in the bag than in breath. The blood glucose increased to a peak about 1 h post-ingestion, but this change was not obviously correlated with temporal changes in any of the compounds in breath or emitted by skin, except for acetone. The decrease in breath acetone was closely mirrored by skin-emitted acetone in three volunteers. Breath and skin acetone also clearly change with blood glucose and further work may ultimately enable inferences to be drawn of the blood glucose concentration from skin or breath measurements in type 1 diabetes. Copyright (C) 2008 John Wiley & Sons, Ltd.

Title: A selected ion flow tube mass spectrometry study of ammonia in mouth- and nose-exhaled breath and in the oral cavity

Authors: Smith, D; Wang, TS; Pysanenko, A; Spanel, P

Reference: RAPID COMMUNICATIONS IN MASS SPECTROMETRY 22 (6):783-789 Doi:1002/rcm.3434 ISSN 0951-4198 2008

Abstract: A study has been carried out, involving three healthy volunteers, of the ammonia levels in breath exhaled via the mouth and via the nose and in the static oral cavity using on-line, selected ion flow tube mass spectrometry (SIFT-MS), obviating the problems associated with sample collection of ammonia. The unequivocal conclusion drawn is that the ammonia appearing in the mouth-exhaled breath of the three volunteers is largely generated in the oral cavity and that the ammonia originating at the alveolar interface in the lungs is typically at levels less than about 100 parts-per-billion, which is a small fraction of the total breath ammonia. This leads to the recommendation that exhaled breath analyses should focus on nose-exhaled breath if the objective is to use breath analysis to investigate systemic, metabolic disease. Copyright (C) 2008 John Wiley & Sons, Ltd.

Title: Experimental and theoretical investigation of electron attachment to SF5Cl

Authors: Van Doren, JM; Miller, TM; Viggiano, AA; Spanel, P; Smith, D; Bopp, JC; Troe, J

Reference: JOURNAL OF CHEMICAL PHYSICS 128 (9): Art  4309 2008

Times Cited: 1

Abstract: Thermal electron attachment to SF5Cl has been studied with the flowing afterglow Langmuir probe technique. The rate coefficient is moderate, 4.8(+/- 1.2)x10(-8) cm(3) s(-1), and invariant with temperature over the temperature range of 300-550 K. The reaction is dissociative, forming mainly SF5-+Cl. Minor yields of Cl- and FCl- were also found. The yields of the minor channels increase slightly with temperature. Statistical unimolecular rate modeling is employed to elucidate the character of the dissociation pathways and to support the assumption that the dissociations involve the formation of metastable anionic SF5Cl-. (C) 2008 American Institute of Physics.

Title: Selected ion flow tube mass spectrometry of 3-hydroxybutyric acid, acetone and other ketones in the headspace of aqueous solution and urine

Authors: Wang, T; Spanel, P; Smith, D

Reference: INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 272 (1):78-85 Doi:1016/j.ijms.2008.01.002 ISSN 1387-3806 2008

Abstract: A study has been carried out of the reactions of three isomers of hydroxybutyric acid, giving special attention to 3-hydroxybutyric acid, 3-HBA, with H3O+ and NO+ ions to acquire the required kinetic data for a selected ion flow tube mass spectrometry, SIFT-MS, search for 3-HBA in the headspace of urine since it is known to be one of the "ketone bodies" important in the diagnosis of ketoacidosis. Thus, the product ions formed in the reactions of the H3O+ and NO+ precursor ions with the three hydroxy acids were established by sampling the headspace above the pure compounds over a range of absolute humidities from 1.5% (ambient air) to 6% (liquid headspace at 37 C and exhaled breath). Then these data, together with the rate coefficients for the reactions estimated by calculation, were used to detect and quantify 3-HBA in the headspace of an aqueous solution of this compound of known concentration and above urine donated by two volunteers. The level of 3-HBA above the urine samples after they were acidified with hydrochloric acid was seen to be typically 40 parts-per-billion, ppb, which is much lower than that for acetone seen to be typically 800ppb. Exploiting the aqueous solution data as a reference, the 3-HBA concentration in the urine samples was estimated to be about 1-2 mmol/L, which is typical of the urine from healthy individuals. (c) 2008 Elsevier B.V. All rights reserved.

Title: The challenge of breath analysis for clinical diagnosis and therapeutic monitoring

Authors: Smith, D; Spanel, P

Reference: ANALYST 132 (5):390-396 Doi:1039/b700542n ISSN 0003-2654 2007

Abstract: The potential of breath analysis for clinical diagnosis and the strengths and weaknesses of the analytical methods used are discussed. Special attention is given to selected ion flow tube mass spectrometry, SIFT-MS, using which on-line real-time analyses of single breath exhalations can be carried out. Illustrative data on the concentration distributions of several breath metabolites amongst the healthy population are presented and their relations to disease when elevated above the normal are alluded to.

Title: Selected ion flow tube mass spectrometry for on-line trace gas analysis in biology and medicine

Authors: Spanel, P; Smith, D

Reference: EUROPEAN JOURNAL OF MASS SPECTROMETRY 13 (1):77-82 Doi:1255/ejms.843 ISSN 1469-0667 2007

Abstract: Selected ion flow tube mass spectrometry, (SIFT-MS), is a technique for simultaneous real-time quantification of several trace gases in air and exhaled breath. It relies on chemical ionization of the trace gas molecules in air/breath samples introduced into helium carrier gas, using H3O+, NO+ and O-2(+) reagent (precursor ions). Reactions between the precursor ions and the trace gas molecules proceed for an accurately defined time, the precursor and product ions being detected and counted by a downstream mass spectrometer. Absolute concentrations of trace gases in single breath exhalation can be determined by SIFT-MS down to parts-per-billion (ppb) levels, obviating sample collection into bags or onto traps. Calibration using chemical standards is not required, as the concentrations are calculated using the known reaction rate constants and measured flow rates and pressures. SIFT-MS has been used for many pilot investigations in several areas of research, especially as a non-invasive breath analysis tool to investigate physiological processes in humans and animals, for clinical diagnosis and for therapeutic monitoring. Examples of the results obtained from several such studies are outlined to demonstrate the potential of SIFT-MS for trace gas analysis of air, exhaled breath and the headspace above liquids.

Title: Microwave plasma ion References for selected ion flow tube mass spectrometry: Optimizing their performance and detection limits for trace gas analysis

Authors: Spanel, P; Dryahina, K; Smith, D

Reference: INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 267117-124 Doi:1016/j.ijms.2007.02.023 ISSN 1387-3806 2007

Abstract: The performance of the ion References used in selected ion flow tube mass spectrometry, SIFT-MS, instruments is paramount in determining their sensitivities and detection limits for trace gas analysis. The microwave discharge plasma ion Reference that is currently used for the production of currents of the precursor H3O+, NO+ and O-2(+) ions for SIFT-MS is described, and the ion chemistry occurring within the plasma and the dissociation of the precursor ions on the helium carrier gas are considered. Thus, it is shown that the most suitable ion Reference gas composition is a mixture comprising maximal water vapour and minimal air at the lowest total pressure at which the discharge is sustained and stable. It is also shown that the injection energies of the precursor ions into the helium carrier gas must be kept low to minimize collisional dissociation of the ions and thus to minimize the fraction of reactive impurity ions in the carrier gas. Under these conditions, count rates greater than 10(6)s(-1) of all three precursor ion species with less than 1% of impurity ions have been achieved, which has moved the detection limit of SIFT-MS analyses of the volatile metabolites present in exhaled breath and ambient air into the 0.1-1 parts-per-billion concentration regime. (C) 2007 Elsevier B.V. All rights reserved.

Title: Increased ratio of extracellular to total body water (ECW/TBW) is related to comorbidity and fluid overload rather loss of lean body mass in haemodialysis (HD) patients

Authors: Chan, C; Davies, SJ; McIntyre, C; Smith, D; Spanel, P

Reference: NEPHROLOGY DIALYSIS TRANSPLANTATION 22314-314 2007

ISSN: 0931-0509

Title: Quantification of breath carbon disulphide and acetone following a single dose of disulfiram (Antabuse) using selected ion flow tube mass spectrometry (SIFT-MS)

Authors: Bloor, RN; Spanel, P; Smith, D

Reference: ADDICTION BIOLOGY 11 (2):163-169 Doi:1111/j.1355-6215.2006.00015.x ISSN 1355-6215 2006

Abstract: Selected ion flow tube mass spectrometry (SIFT-MS) has been used to measure simultaneously the concentrations of both carbon disulphide and acetone in exhaled breath following the ingestion of a single dose of disulfiram (Antabuse). Carbon disulphide is a product of the metabolism of disulfiram and is excreted mainly through the lungs. Acetone is a product of normal metabolism and appears in the breath of all individuals. These breath analyses were performed in single exhalations and the results were available in real time. The levels of breath acetone and carbon disulphide were compared with levels obtained from a control subject who had not ingested disulfiram. Breath carbon disulphide was seen to increase from 15 p.p.b. to 618 p.p.b. over a 28-hour period, in the single individual tested, following ingestion of disulfiram, while acetone levels increased from 300 p.p.b. (normal) to over 4000 p.p.b. (greatly elevated). No such increases were seen in the breath of the control subject over the same period. An obvious positive correlation between breath carbon disulphide and acetone concentrations following disulfiram ingestion is seen and discussed.