1. P. Španěl, D. Smith. "Progress in SIFT-MS; breath analysis and other applications." Mass Spectrometry Reviews 30 (2011) 236-267. http://dx.doi.org/10.1002/mas.20303
The development of selected ion flow tube mass spectrometry, SIFT-MS, is described from its inception as the modified very large SIFT instruments used to demonstrate the feasibility of SIFT-MS as an analytical technique, towards the smaller but bulky transportable instruments and finally to the current smallest Profile 3 instruments that have been located in various places, including hospitals and schools to obtain on-line breath analyses. The essential physics and engineering principles are discussed, which must be appreciated to design and construct a SIFT-MS instrument. The versatility and sensitivity of the Profile 3 instrument is illustrated by typical mass spectra obtained using the three precursor ions H3O+, NO+ and O-2(+center dot), and the need to account for differential ionic diffusion and mass discrimination in the analytical algorithms is emphasized to obtain accurate trace gas analyses. The performance of the Profile 3 instrument is illustrated by the results of several pilot studies, including (i) on-line real time quantification of several breath metabolites for cohorts of healthy adults and children, which have provided representative concentration/population distributions, and the comparative analyses of breath exhaled via the mouth and nose that identify systemic and orally-generated compounds, (ii) the enhancement of breath metabolites by drug ingestion, (iii) the identification of HCN as a marker of Pseudomonas colonization of the airways and (iv) emission of volatile compounds from urine, especially ketone bodies, and from skin. Some very recent developments are discussed, including the quantification of carbon dioxide in breath and the combination of SIFT-MS with GC and ATD, and their significance. Finally, prospects for future SIFT-MS developments are alluded to. (C) 2010 Wiley Periodicals, Inc., Mass Spec Rev 30: 236-267, 2011
2. M. Ferus, P. Kubelik, K. Kawaguchi, K. Dryahina, P. Španěl, S. Civis. "HNC/HCN Ratio in Acetonitrile, Formamide, and BrCN Discharge." Journal of Physical Chemistry A 115 (2011) 1885-1899. http://dx.doi.org/10.1021/jp1107872
Time-resolved Fourier transform (FT) spectrometry was used to study the dynamics of radical reactions forming the HCN and HNC isomers in pulsed glow discharges through vapors of BrCN, acetonitrile (CH3CN), and formamide (HCONH2). Stable gaseous products of discharge chemistry were analyzed by selected ion flow tube mass spectrometry (SIFT-MS). Ratios of concentrations of the HNC/HCN isomers obtained using known transition dipole moments of rovibrational cold bands v(1) were found to be in the range 2.2-3%. A kinetic model was used to assess the roles the radical chemistry and ion chemistry play in the formation of these two isomers. Exclusion of the radical reactions from the model resulted in a value of the HNC/HCN ratio 2 orders of magnitude lower than the experimental results, thus confirming their dominant role. The major process responsible for the formation of the HNC isomer is the reaction of the HCN isomer with the H atoms. The rate constant determined using the kinetic model from the present data for this reaction is 1.13 (+/-0.2) x 10(-13) cm(3) s(-1).
3. A. Olivares, K. Dryahina, J.L. Navarro, D. Smith, P. Španěl, M. Flores. "SPME-GC-MS versus Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) Analyses for the Study of Volatile Compound Generation and Oxidation Status during Dry Fermented Sausage Processing." Journal of Agricultural and Food Chemistry 59 (2011) 1931-1938. http://dx.doi.org/10.1021/jf104281a
The use of selected ion flow tube mass spectrometry (SIFT-MS) and gas chromatography mass spectrometry together with solid phase microextraction (GC-MS-SPME) has been compared in the analysis of volatile compounds during dry fermented sausage processing. Thus, the headspace (HS) of samples of dry fermented sausages with different fat contents was analyzed during their manufacture using both techniques, and significant and positive correlations were found between SIFT-MS and SPME-GC-MS measurements for the compounds pentanal, hexanal, 2-heptenal, octanal, 2-nonenal, 2-butanone, 2-pentanone, ethanol, acetic acid, and hexanoic acid. The oxidative status of fermented sausages during processing was also evaluated, and a significant correlation was obtained between the HS concentration of lipid autoxidation volatile compounds measured by SIFT-MS and SPME-GC-MS and the level of thiobarbituric acid reactive substances (TBARS) in the sausage. The hexanal measured by SIFT-MS resulted in a higher correlation coefficient (r = 0.936) than that obtained using SPME-GC-MS (r = 0.927). SIFT-MS is shown to be a fast, real time analytical technique for monitoring changes in the profile of volatile compounds in dry fermented sausages during processing and a useful tool to evaluate the oxidative status of meat products.
4. P. Španěl, V. Shestivska, T.W.E. Chippendale, D. Smith. "Determination of the Deuterium Abundances in Water from 156 to 10,000 ppm by SIFT-MS." Journal of the American Society for Mass Spectrometry 22 (2011) 179-186. http://dx.doi.org/10.1007/s13361-010-0019-2
In response to a need for the measurement of the deuterium (D) abundance in water and aqueous liquids exceeding those previously recommended when using flowing afterglow mass spectrometry (FA-MS) and selected ion flow tube mass spectrometry (SIFT-MS) (i.e. 1000 parts per million, ppm), we have developed the theory of equilibrium isotopic composition of the product ions on which these analytical methods are based to encompass much higher abundances of D in water up to 10,000 ppm (equivalent to 1%). This has involved an understanding of the number density distributions of the H, D, O-16, O-17 and O-18 isotopes in the isotopologues of H3O+(H2O)(3) hydrated ions (i.e. H9O (4) (+) cluster ions) at mass-to-charge ratios (m/z) of 73, 74 and 75, the relative ion number densities of which represent the basis of FA-MS and SIFT-MS analyses of D abundance. Specifically, an extended theory has been developed that accounts for the inclusion of D atoms in the m/z 75 ions, which increasingly occurs as D abundance in the water is increased, and which is used as a reference signal for the m/z 74 ions in the measurement of D abundance. In order to investigate the efficacy of this theory, experimental measurements of deuterium abundance in standard mixtures were made by the SIFT-MS technique using two similar instruments and the results compared with the theory. It is demonstrated that the parameterization of experimental data can be used to formulate a simple calculation algorithm for real-time SIFT-MS measurements of D abundance to an accuracy of 1% below 1000 ppm and degrades to about 2% at 10,000 ppm.
5. K. Sovova, K. Dryahina, P. Španěl. "Selected ion flow tube (SIFT) studies of the reactions of H3O+, NO+ and O-2(+center dot) with six volatile phytogenic esters." International Journal of Mass Spectrometry 300 (2011) 31-38. http://dx.doi.org/10.1016/j.ijms.2010.11.021
The selected ion flow tube (SIFT) was used to study the reactions of the three SIFT-MS precursor ions H3O+, NO+ and O-2(+center dot) with six phytogenic esters: hexyl acetate, phenethyl acetate, benzyl acetate, methyl salicylate, methyl benzoate and benzyl benzoate. These compounds are emitted into the atmosphere by various species of plants and play a role in communication between individual plants and also amongst different species. Thus, it is necessary to know the rate constants and branching ratios of the different ion products of these reactions for identification and quantification by SIFT-MS. The results of this study show that the reactions of H3O+ with the esters proceed via proton transfer, which is non-dissociative for methyl salicylate, entirely dissociative for benzyl benzoate and partly dissociative for the remaining four esters. All protonated esters readily associate with water molecules with the notable exception of methyl salicylate. All six NO reactions result in formation of adduct ions in parallel with charge transfer or with reactions leading to fragment ions. All six O-2(+center dot) reactions proceed by charge transfer with the production of one or two major fragment ions; the parent molecular radical cation is formed in three reactions only. Kinetic library entries allowing unambiguous quantification of the six esters by SIFT-MS are presented together with their experimental validation. (C) 2010 Elsevier B.V. All rights reserved.
6. M. Civis, S. Civis, K. Sovova, K. Dryahina, P. Španěl, M. Kyncl. "Laser Ablation of FOX-7: Proposed Mechanism of Decomposition." Analytical Chemistry 83 (2011) 1069-1077. http://dx.doi.org/10.1021/ac1028769
A novel high-energy explosive material, FOX-7 (1,1-diamino-2, 2-dinitroethylene), was studied using a combination of laser-induced breakdown spectroscopy (LIBS) and selected ion flow tube mass spectrometry (SIFT-MS). The LIBS technique uses short laser pulses (an ArF excimer laser) as the energy source to convert small quantities of a sample into plasma and to induce the emission of its molecular fragments or atoms. SIFT-MS is a novel method for absolute quantification based on chemical ionization using three reagent ions, with the ability to determine concentrations of trace gases and vapors of volatile organic compounds in real time. SIFT-MS was used to study the release of NO, NO2, HCN, HONO, HCHO, CH3CH2OH, and C2H2 after laser ablation of the explosive compound FOX-7 in solid crystalline form. The radiation emitted after excitation was analyzed using a time resolved UV-vis spectrometer with an ICCD detector. The electronic bands of CN (388 nm), OH (308.4 nm), and NO (237.1 nm) radicals and the atomic lines of C, N, and H were identified.
7. D. Smith, P. Španěl, A.A. Fryer, F. Hanna, G.A.A. Ferns. "Can volatile compounds in exhaled breath be used to monitor glycaemic control in diabetes mellitus?" Jounal of Breath Research 5 (2011) 022001. http://dx.doi.org/10.1088/1752-7155/5/2/022001
Although it has been known for centuries that there are compounds in exhaled breath that are altered in disease, it is only in the last few decades that it has been possible to measure them with sufficient accuracy and precision to make them clinically useful. The clinical utility of breath analysis has also been limited by the practical difficulties of collecting representative breath samples, free from contaminants. More recent methods of breath analysis have allowed real-time analysis of breath, eliminating the need for sample collection, and therefore potentially allowing the rapid feedback of results to patient and clinician. One possible future application of breath analysis may be the monitoring of metabolic control in patients with diabetes mellitus. This perspective article provides an overview of the studies of breath analysis in diabetes, focusing on the breath metabolites; acetone, isoprene and also methyl nitrate that have previously been reported to be altered in diabetes, highlighting the factors that may potentially confound their interpretation. Specific attention is given to selected ion flow tube mass spectrometry (SIFT-MS) and proton transfer reaction mass spectrometry (PTR-MS), because they are techniques that have been developed specifically for the absolute quantification of breath metabolites in real time, although reference is made to some of the alternative techniques, including sensors and optical devices. Whilst breath analysis, using SIFT-MS, PTR-MS and other sensitive techniques, can potentially be used for the non-invasive monitoring of metabolic conditions that may include diabetes mellitus, further work is required in terms of the clinical and analytical validation. Furthermore, it is unclear at present what breath metabolites should be monitored and what factors may confound their interpretation. Although a non-invasive method of monitoring glycaemic control is clearly desirable, it will be important to demonstrate its analytical comparability with the well-established and validated methods for blood glucose measurement.
8. D. Smith, T.W.E. Chippendale, P. Španěl. "Selected ion flow tube, SIFT, studies of the reactions of H3O+, NO+ and O2+ with some biologically active isobaric compounds in preparation for SIFT-MS analyses." International Journal of Mass Spectrometry In Press, doi:10.1016/j.ijms.2011.01.005 (2011). http://dx.doi.org/10.1016/j.ijms.2011.01.005
A study of the reactions of H3O+, NO+ and O2+ ions with two groups of four isobaric, biologically active compounds with molecular weights, MW, of 86u and 88u has been carried out using the selected ion flow tube, SIFT, technique in preparation for the analyses of these compounds in the headspace of bacterial and cell cultures using SIFT-MS. These compounds are: MW 86u: 2,3 butanedione (diacetyl), C4H6O2; allyl ethyl ether, C5H10O, cyclopropane carboxylic acid, C4H6O2: [gamma]-butyrolactone, C4H6O2. MW 88u: 3-hydroxybutanone (acetoin), C4H8O2; n-butyric acid, C4H8O2; ethyl acetate, C4H8O2; pyruvic acid, C3H4O3. All 24 reactions proceed at the gas kinetic rate, the dominant primary product ions of the H3O+ reactions being the protonated reactant molecules, MH+ with a common mass-to-charge ratio, m/z, in each group of isobaric compounds; those of the NO+ reactions being the adduct ions, NO+M, also with a common m/z value; for the O2+ ion reactions, fragmentation ions of the nascent parent ion M+ are produced. SIFT-MS analysis of each compound individually is straightforward, but when more than one isobaric compound is present, SIFT-MS analyses become more challenging. However, hydration of some, but not all, of the primary MH+ and NO+M primary ions occurs, variously generating MH+(H2O)1,2 and NO+MH2O ions, and the occurrence/non-occurrence of these hydrates can assist in distinguishing between some of the isobaric compounds. From the kinetic data obtained in this study, the required SIFT-MS kinetics library entries for each compound can be constructed that allow their quantification. As an example, SIFT-MS spectra are presented relating to the analysis of the headspace of incubated yoghurt, which show the presence of several volatile organic compounds, including acetoin and diacetyl.
9. F.J. Gilchrist, A. Alcock, J. Belcher, M. Brady, A. Jones, D. Smith, P. Španěl, K. Webb, W. Lenney. "Variation in cyanide production between different strains of Pseudomonas aeruginosa." European Respiratory Journal (2011) In press. http://dx.doi.org/10.1183/09031936.00166510
10. D. Smith, P. Španěl. "Ambient analysis of trace compounds in gaseous media by SIFT-MS." Analyst 136 (2011) 2009-2032. http://dx.doi.org/10.1039/C1AN15082K
The topic of ambient gas analysis has been rapidly developed in the last few years with the evolution of the exciting new techniques such as DESI, DART and EESI. The essential feature of all is that analysis of trace gases can be accomplished either in the gas phase or those released from surfaces, crucially avoiding sample collection or modification. In this regard, selected ion flow tube mass spectrometry, SIFT-MS, also performs ambient analyses both accurately and rapidly. In this focused review we describe the underlying ion chemistry underpinning SIFT-MS through a discourse on the reactions of different classes of organic and inorganic molecules with H3O+, NO+ and O2+˙ studied using the SIFT technique. Rate coefficients and ion products of these reactions facilitate absolute SIFT-MS analyses and can also be useful for the interpretation of data obtained by the other ambient analysis methods mentioned above. The essential physics and flow dynamics of SIFT-MS are described that, together with the reaction kinetics, allow SIFT-MS to perform absolute ambient analyses of trace compounds in humid atmospheric air, exhaled breath and the headspace of aqueous liquids. Several areas of research that, through pilot experiments, are seen to benefit from ambient gas analysis using SIFT-MS are briefly reviewed. Special attention is given to exhaled breath and urine headspace analysis directed towards clinical diagnosis and therapeutic monitoring, and some other areas researched using SIFT-MS are summarised. Finally, extensions to current areas of application and indications of other directions in which SIFT-MS can be exploited for ambient analysis are alluded to.
11. K. Dryahina, D. Smith, P. Španěl. "Quantification of methane in humid air and exhaled breath using selected ion flow tube mass spectrometry." Rapid Communications in Mass Spectrometry 24 (2010) 1296-1304. http://dx.doi.org/10.1002/rcm.4513
12. B.K. Tan, D. Smith, P. Španěl, S.J. Davies. "Dispersal kinetics of deuterated water in the lungs and airways following mouth inhalation: real-time breath analysis by flowing afterglow mass spectrometry (FA-MS)." Journal of Breath Research 4 (2010) 017109. http://dx.doi.org/10.1088/1752-7155/4/1/017109
Pulmonary oedema is a medical condition characterized by abnormal accumulation of fluid in the extravascular space in the alveoli. Effective oxygenation is impaired and this leads to significant short-and long-term morbidity and mortality. The detection and monitoring of pulmonary oedema by measuring lung water volume is therefore crucial in the initiation and guidance of therapeutic intervention. The current gold standard bedside measurement of extravascular lung water volume (EVLW) is the dilution method using various indicators, but despite the good correlation of the results with those obtained using the post-mortem gravimetric method, the invasiveness of the dilution technique limits its general application in the wider clinical setting. In the present preliminary experiments, the dispersal kinetics of deuterium (actually HDO) in exhaled breath of three healthy participants following the inhalation of deuterium oxide (D2O) vapour are explored as monitored using flowing afterglow mass spectrometry (FA-MS). Here, we present the basic ideas of lung water estimation using this novel technique, and briefly discuss its limitations and required future work.
13. A. Olivares, K. Dryahina, J.L. Navarro, M. Flores, D. Smith, P. Španěl. "Selected Ion Flow Tube-Mass Spectrometry for Absolute Quantification of Aroma Compounds in the Headspace of Dry Fermented Sausages." Analytical Chemistry 82 (2010) 5819-5829. http://dx.doi.org/10.1021/ac1009723
The meat industry is interested in rapid control of the sensory quality of meat products. Selected ion flow tube mass spectrometry (SIFT-MS) has been applied to the rapid, real-time quantification of 31 volatile aroma compounds present in the headspace (HS) of dry fermented sausages. Three batches of fermented sausages with different fat contents (10, 20, and 30%) were monitored throughout the processing time. SIFT-MS revealed significant changes in the concentration of all the aroma compounds during the processing time. Moreover, among the various batches of the sausages, significant differences were revealed in their HS concentration of butanal, 2-pentenal, hexanal, 2-butanone, 2,3-butanedione, ethanol, ethyl formate, hexanoic acid, and dimethyl disulfide. In addition, highly volatile compounds were detected and quantified using our real-time SIFT-MS technique that are apparently not generally seen by trace gas extraction and GC techniques.
14. J. Zabka, J. Roithova, P. Španěl, Z. Herman. "Dynamics of Formation of Products D2CN+, DCN+, and CD3+ in the Reaction of N+ with CD4: A Crossed-Beam and Theoretical Study." Journal of Physical Chemistry a (2010) 1384-1391. http://dx.doi.org/10.1021/jp9069493
The formation of D2CN+ in the reaction of N+ (P-3) with CD4 was studied using the crossed beam technique at collision energies of 3.66 and 4.86 eV. The experiments were complemented by calculations of stationary points on the triplet hypersurface of the system. The scattering data showed that the reaction proceeds by the formation of two intermediate complexes having different lifetimes: it long-lived statistical intermediate and short-lived complex (mean lifetime about one period of an average rotation) with more energy in translation than the statistical complex. Comparison with theoretical Calculations suggests that the long-lived complex leads the CDND+ isomer of the product ion, whereas the short-lived complex leads prevailingly to the CD2N+ isomer. The product DCN+ results from further decomposition of the primary product D2CN+, whereas CD3+ is formed both by a hydride-ion transfer and it long-lived complex decomposition.
15. B. John, B.K. Tan, S. Dainty, P. Španěl, D. Smith, S.J. Davies. "Plasma volume, albumin, and fluid status in peritoneal dialysis patients." Clinical Journal of the American Society of Nephrology 5 (2010) 1463-1470. http://dx.doi.org/10.2215/cjn.09411209
Background and objectives: Peritoneal dialysis (PD) patients may be overhydrated especially when inflammation is present. We hypothesized that patients with a plasma albumin below the median value would have measurable overhydration without a proportional increase in plasma volume (PV). Design, setting, participants, & measurements: We investigated a cross-sectional sample of 46 prevalent PD patients powered to detect a proportional increase in PV associated with whole body overhydration and hypoalbuminemia. PV was determined from I-125-labeled albumin dilution, absolute total body water from D dilution (TBWD), and relative hydration from multifrequency bioimpedance analysis (BIA; Xitron 4200) expressed as the extracellular water (ECW):TBWBIA ratio. Results: Whereas patients with plasma albumin below the median (31.4 g/dl) were overhydrated as determined both by BIA alone (ECW:TBWBIA 0.49 versus 0.47, P < 0.036) and the difference between estimated TBWBIA and measured TBWD (3.55 versus 0.94 L, P = 0.012), corrected PV was not different (1463 versus 1482 ml/m(2), NS). Mean PV was not different from predicted, and its variance did not correlate with any other clinical measures. Multivariate analysis showed that the only independent predictor of whole body overhydration was reduced plasma albumin. Conclusions: Hypoalbuminemia is an important determinant of tissue overhydration in PD patients. This overhydration is not associated with an increased plasma volume. Attempts to normalize the ECW:TBW ratio in hypoalbuminemic, inflamed PD patients may lead to hypovolemia and loss of residual renal function. Clin J Am Soc Nephrol 5: 1463-1470, 2010. doi: 10.2215/CJN.09411209
16. D. Smith, A. Pysanenko, P. Španěl. "Kinetics of ethanol decay in mouth- and nose-exhaled breath measured on-line by selected ion flow tube mass spectrometry following varying doses of alcohol." Rapid Communications in Mass Spectrometry 24 (2010) 1066-1074. http://dx.doi.org/10.1002/rcm.4481
17. D. Smith, P. Španěl, J. Sule-Suso. "Advantages of breath testing for the early diagnosis of lung cancer." Expert Review of Molecular Diagnostics 10 (2010) 255-257. http://dx.doi.org/10.1586/erm.10.16
18. K. Sovova, K. Dryahina, P. Španěl, M. Kyncl, S. Civis. "A study of the composition of the products of laser-induced breakdown of hexogen, octogen, pentrite and trinitrotoluene using selected ion flow tube mass spectrometry and UV-Vis spectrometry." Analyst (2010) 1106-1114. http://dx.doi.org/DOI 10.1039/b926425f
Four types of explosives were studied using a combination of Laser Induced Breakdown Spectroscopy (LIBS) and Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). The LIBS technique uses short laser pulses (ArF excimer laser) as the energy source to convert small amounts samples into plasma and to produce the emission from their molecular fragments or atoms. SIFT-MS is a novel method for absolute quantification based on chemical ionization using three precursor ions, with the capability to determine concentrations of trace gases and vapours of volatile organic compounds in real time. This is the first time that SIFT-MS has been used to study the release of NO, NO2, HCN, HNO3, HONO, HCHO and C2H2 after a laser-induced breakdown of pure explosive compounds HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclo-octane), RDX (1,3,5-trinitro-2-oxo-1,3,5-triazacyclo-hexane), PETN (pentaerithrityl-tetranitrate) and TNT (2,4,6-trinitrotoluene) in solid form. The radiation emitted after excitation was analysed using a time resolving UV-Vis spectrometer with a ICCD detector. Electronic bands of the CN radical (388 nm), the Swan system of the C-2 radical (512 nm), the NH radical (336 nm), the OH radical (308.4 nm) and atomic lines of oxygen, nitrogen and hydrogen were identified. Vibrational and excitation temperatures were determined from the intensity distributions and a scheme of chemical reactions responsible for the formation of the observed species was proposed.
19. D. Smith, P. Španěl, B. Enderby, W. Lenney, C. Turner, S.J. Davies "Isoprene levels in the exhaled breath of 200 healthy pupils within the age range 7–18 years studied using SIFT-MS." Journal of Breath Research 4 (2010) 017101. http://dx.doi.org/10.1088/1752-7155/4/1/017101
20. K. Dryahina, F. Pehal, D. Smith, P. Španěl. "Quantification of methylamine in the headspace of ethanol of agricultural origin by selected ion flow tube mass spectrometry." International Journal of Mass Spectrometry 286 (2009) 1-6. http://dx.doi.org/10.1016/j.ijms.2009.06.002
Selected ion flow tube mass spectrometry, SIFT-MS. has been used to investigate if absolute levels of trace compounds in the headspace of ethanol/water vapour mixture can be quantified. This case study was directed towards the analysis of methylamine in distilled ethanol of agricultural origin because of its relevance to quality control legislation in the distillery industry. This has required a detailed study of the ion chemistry occurring - initiated by H3O+ precursor ions - when ethanol/water vapour mixtures are introduced into the H3O+/helium carrier gas swarm and has resulted in the construction of a full scheme of the complex ionic reactions that occur. It has been found that under the SIFT-MS flow reactor conditions (He pressure 130 Pa and temperature 299 K) the terminating ions of the several parallel and sequential reactions that occur are the proton bound ethanol clusters ions. C2H5OH2+(C2H5OH)(n). with n = 1,2,3, proton bound trimer (n = 2) being the dominant species. These ethanol cluster ions can be used as precursor (reagent) ions for the chemical ionisation of the methylamine present in the ethanol/water vapour, which produces two characteristic product ions CH3NH2H+(C2H5OH)(1,2) that are used for the methylamine analysis. The ratio of the product ion count rate to the precursor ion count rate is used in an analogous way to the routinely used for SIFT-MS analyses to quantify the methylamine concentration. The results of calibration experiments show that using SIFT-MS it is possible to quantify methylamine in liquid ethanol/water mixtures at levels of 0.1 mg/L or greater. (C) 2009 Elsevier B.V. All rights reserved.
21. C. Chan, C. McIntyre, D. Smith, P. Španěl, S.J. Davies. "Combining near-subject absolute and relative measures of longitudinal hydration in hemodialysis." Clinical Journal of the American Society of Nephrology 4 (2009) 1791-1798. http://dx.doi.org/10.2215/cjn.02510409
Background and objectives: The feasibility and additional value of combining bioimpedance analysis (BIA) with near-subject absolute measurement of total body water using deuterium dilution (TBWD) in determining longitudinal fluid status was investigated. Design, setting, participants, & measurements: Fifty-nine hemodialysis patients (17 female; age 58.4 +/- 16.1 yr; body mass index 27.0 +/- 5.4) were enrolled into a 12-mo, two-center, prospective cohort study. Deuterium concentration was measured in breath by flowing-afterglow mass spectrometry using a validated protocol ensuring full equilibration with the TBW; BIA was measured using a multifrequency, multisegmental device. Comorbidity was quantified by the Stoke score. Clinicians were blinded to body composition data. Results: At baseline and 12 mo, there was an incremental discrepancy between TBWBIA and TBWD volumes such that greater comorbidity was associated with increasing overhydration. Forty-three patients who completed the study had no longitudinal differences in the prescribed or achieved postdialysis weights. In contrast, TBWD increased without a change in TBWBIA (mean difference -0.10 L). Changes in TBW and lean body mass differed according to baseline comorbidity; without comorbidity, BIA also identified an increase in TBW and lean body mass, whereas with increasing comorbid burden, BIA failed to demonstrate increases in tissue hydration identified by TBWD. Conclusions: Combined near-patient measurements of absolute and BIA-estimated TBW are achievable in a dialysis facility by identifying changes in body composition not fully appreciated by routine assessment. BIA underestimates tissue overhydration that is associated with comorbidity, resulting in reduced sensitivity to longitudinal increases during a 12-mo period. Clin J Am Soc Nephrol 4: 1791-1798, 2009. doi: 10.2215/CJN.02510409
22. D. Smith, A. Pysanenko, P. Španěl. "The quantification of carbon dioxide in humid air and exhaled breath by selected ion flow tube mass spectrometry." Rapid Communications in Mass Spectrometry 23 (2009) 1419-1425. http://dx.doi.org/10.1002/rcm.4016
The reactions of carbon dioxide, CO2, with the precursor ions used for selected ion flow tube mass spectrometry, SIFT-MS, analyses, viz. H3O+, NO+ and O-2(+), are so slow that the presence of CO2 in 2 exhaled breath has, until recently, not had to be accounted for in SIFT-MS analyses of breath. This has, however, to be accounted for in the analysis of acetaldehyde in breath, because an overlap occurs of the monohydrate of protonated acetaldehyde and the weakly bound adduct ion, H3O+CO2, formed by the slow association reaction of the precursor ion H3O+ With CO2 molecules. The understanding of the kinetics of formation and the loss rates of the relevant ions gained from experimentation using the new generation of more sensitive SIFT-MS instruments now allows accurate quantification of CO2 in breath using the level of the H3O+CO2 adduct ion. However, this is complicated by the rapid reaction of H3O+CO2 with water vapour molecules, H2O, that are in abundance in exhaled breath. Thus, a study has been carried out of the formation of this adduct ion by the slow three-body association reaction of H3O+ with CO2 and its rapid loss in the two-body reaction with H2O molecules. It is seen that the signal level of the H3O+CO2 adduct ion is sensitively dependent on the humidity (H2O concentration) of the sample to be analysed and a functional form of this dependence has been obtained. This has resulted in an appropriate extension of the SIFT-MS software and kinetics library that allows accurate measurement of CO2 levels in air samples, ranging from very low percentage levels (0.03% typical of tropospheric air) to the 6% level that is about the upper limit in exhaled breath. Thus, the level of CO2 can be traced through single time exhalation cycles along with that of water vapour, also close to the 6% level, and of trace gas metabolites that are present at only a few parts-per-billion. This has added a further dimension to the analysis of major and trace compounds in breath using SIFT-MS. Copyright (C) 2009 John Wiley & Sons, Ltd.
23. D. Smith, A. Pysanenko, P. Španěl. "Ionic diffusion and mass discrimination effects in the new generation of short flow tube SIFT-MS instruments." International Journal of Mass Spectrometry 281 (2009) 15-23. http://dx.doi.org/10.1016/j.ijms.2008.11.007
The major thrust of this paper is to describe how the current selected ion flow tube mass spectrometry (SIFT-MS) Profile 3 instruments can be configured to provide reliable quantification of the trace gases present in air and exhaled breath by accounting for the phenomena of differential diffusion of the analytical precursor and product ions in the flow tube reactor and mass discrimination in the ion sampling/analytical quadrupole mass spectrometer/detection system. If not accounted for these phenomena, especially the latter, can result in serious errors in quantification. Hence, it is described how H3O+ precursor ions are totally converted to a range of product ions within the mass-to-charge ratio, m/z, range from 18 to 201 and, thus, how the ion currents collected by the downstream ion sampling orifice disc and the count rates of these ions as determined by the analytical detection system at the various m/z are used to provide values of both the diffusion enhancement coefficient, De, and the mass discrimination factor, M-r, that are required to allow accurate trace gas analyses. It is indicated how all such SIFT-MS instruments can be properly configured using a similar but abbreviated procedure. Finally, it is shown how the properly configured Profile 3 instrument provides consistent and reliable analyses of acetone using H3O+, NO+ and O-2(+), 2-pentanone and 2-hexanone using H3O+ and NO+, and ammonia using H3O+ and O-2(+) precursor ions in (relatively dry) air samples and in (humid) single breath exhalations. (C) 2008 Elsevier B.V. All rights reserved.
24. P. Španěl, D. Smith. "Influence of weakly bound adduct ions on breath trace gas analysis by selected ion flow tube mass spectrometry (SIFT-MS)." International Journal of Mass Spectrometry 280 (2009) 128-135. http://dx.doi.org/10.1016/j.ijms.2008.07.021
This paper describes how weakly bound adduct ions form when the precursor ions used in selected ion flow mass spectrometry, SIFT-MS, analyses, viz. H3O+, NO+ and O-2(+), associate with the major components of air and exhaled breath, N-2, O-2 and CO2. These adduct ions, which include H3O+N2, H3O+CO2, NO+CO2, O-2+O-2 and O-2+CO2. are clearly seen when dry air containing 5% CO2 (typical of that in exhaled breath) is analysed using SIFT-MS. These adduct ions must not be misinterpreted as characteristic product ions of trace gases; if so, serious analytical errors can result. However, when exhaled breath is analysed these adduct ions are partly removed by ligand switching reactions with the abundant water molecules and the problems they represent are alleviated. But the small fractions of the adduct ions that remain in the SIFT-MS spectra, and especially when they are isobaric with genuine characteristic product ion of breath trace gases, can result in erroneous quantifications; such is the case for H3O+N2 interfering with breath ethanol analysis and H3O+CO2 with breath acetalclehyde analysis. However, these difficulties can be overcome when the isobaric adduct ions are properly recognised and excluded from the analyses; then these two important compounds can be properly quantified in breath. The presence Of O2+CO2 in the product ion spectra interferes with the analysis of CS2 present at low levels in exhaled breath. It is likely that similar problems will occur as other trace compounds are detected in exhaled breath when consideration will have to be given to the possibility of overlapping between their characteristic product ions and ions produced by hitherto unknown reactions. Similar problems are evident in other systems; for example, H3O+CH4 adduct ions are observed in both SIFT-MS analyses of methane rich mixtures like biologically generated waste gases and in model planetary atmospheres. (C) 2008 Elsevier B.V. All rights reserved.
25. S. Civis, M. Civis, R. Rasin, M. Kamas, K. Dryahina, P. Španěl, L. Juha, M. Ferus (2009). Spectroscopic Investigations of High-Power Laser Sparks in Gas Mixtures Containing Methane: A Laboratory Model of Energetic Events in Strongly Reduced Planetary Atmospheres. Origins of Life and Evolution of Biospheres. 39: 217-217.
26. K. Sovova, I. Matulkova, M. Kamas, K. Dryahina, P. Španěl, L. Juha, S. Civis (2009). SIFT-MS Analysis of Molecular Gas Mixtures Exposed to High-Power Laser Plasmas: Laboratory Simulation of High-Energy-Density Events in Early Earth's Atmospheres. Origins of Life and Evolution of Biospheres. 39: 249-250.
27. A. Pysanenko, P. Španěl, D. Smith. "Analysis of the isobaric compounds propanol, acetic acid and methyl formate in humid air and breath by selected ion flow tube mass spectrometry, SIFT-MS." International Journal of Mass Spectrometry 285 (2009) 42-48. http://dx.doi.org/10.1016/j.ijms.2009.04.002
Numerous analyses of exhaled breath using selected ion flow tube mass spectrometry, SIFT-MS, over the last few years have revealed the presence of volatile compounds with molecular weight 60 and the concern has been to identify which of the isobaric compounds from the set of 1-propanol, 2-propanol. aceticacid and methyl formate are present in human breath. The problem is compounded by the formation of hydrates of the characteristic primary product ions of the reactions of the H3O+ and NO+ precursor ions with these compounds, this being particularly efficient for humid samples such as exhaled breath. Thus, the resulting product ion spectra are complex and choices have to be made as to which of the characteristic product ions and their hydrates can best be used for the quantitative analyses. To facilitate this choice for the particular problem of identifying and quantifying the four aforementioned isobaric compounds, a study has been made of the ion chemistry of H3O+ and NO+ with the two propanol isomers, acetic acid and methyl formate for increasing sample humidity up to that of exhaled breath, which is about 6% by volume. The problems involved in the separate analysis of propanol have been met and solved by previous SIFT-MS studies and now the present study has revealed how acetic acid and methyl formate can be separately identified in a humid mixture using NO+ precursor ions only. Following this work, the kinetics database entries for the SIFT-MS analyses of these compounds in breath have been constructed and the analysis of the exhaled breath of five healthy volunteers showed that, in addition to the propanol isomers, acetic acid was present at levels typically within the range from 30 to 60 parts-per-billion by volume and that methyl formate was not present above the limit of detection. (C) 2009 Elsevier B.V. All rights reserved.
28. A. Pysanenko, T. Wang, P. Španěl, D. Smith. "Acetone, butanone, pentanone, hexanone and heptanone in the headspace of aqueous solution and urine studied by selected ion flow tube mass spectrometry." Rapid Communications in Mass Spectrometry 23 (2009) 1097-1104. http://dx.doi.org/10.1002/rcm.3963
Urine is commonly analysed in clinical practice by a variety of liquid-phase techniques to check for excessive ketone bodies, proteins and salts to name just a few compounds. However, little work has been carried out to measure the volatile compounds emitted by urine since these do not yet have an established role in clinical diagnosis. There is, however, a growing body of evidence that these volatile compounds can be indicators of adverse physiological conditions and disease and with the advent of sensitive gas-phase analytical methods they can be quickly quantified in urine headspace and potentially provide valuable support for clinical diagnosis. Thus, we are developing selected ion flow tube mass spectrometry, SIFT-MS, for the real-time analysis of urine headspace, ultimately to support rapid diagnosis in the clinical environment. In this paper we focus on volatile ketones in the headspace of aqueous solutions and urine donated by three healthy volunteers. Using SIFT-MS, we have unambiguously quantified in urine headspace acetone, by far the most abundant ketone, butanone, pentanone, hexanone and heptanone using NO+ precursor ions. Further to this, we have determined the Henry's Law coefficients, HLC, for these ketones in aqueous solution to allow the liquid-phase concentrations in urine to be estimated from headspace levels of their vapours. In addition, the influence of the addition of physiological amounts of dissolved urea, sodium chloride and hydrochloric acid on the partitioning of these ketones between the aqueous phase and gas phase has been investigated and found to be small, which gives greater credence to the use of the HLC obtained using aqueous solutions for the estimation of ketone concentrations in urine. Finally, parallel measurements of the levels of acetone in exhaled breath and urine headspace have been obtained and shown to be very similar, which gives support to the previous deduction from breath analysis that acetone is a truly systemic compound. Copyright (C) 2009 John Wiley & Sons, Ltd.
29. B. Enderby, W. Lenney, M. Brady, C. Emmett, P. Španěl, D. Smith. "Concentrations of some metabolites in the breath of healthy children aged 7-18 years." Journal of Breath Research 3 (2009) 036001. http://dx.doi.org/10.1088/1752-7155/3/3/036001
30. J. Sule-Suso, A. Pysanenko, P. Španěl, D. Smith. "Quantification of acetaldehyde and carbon dioxide in the headspace of malignant and non-malignant lung cells in vitro by SIFT-MS." Analyst 134 (2009) 2419-2425. http://dx.doi.org/10.1039/b916158a
Previous studies using selected ion flow tube mass spectrometry, SIFT-MS, showed that CALU-1 lung cancer cell cultures emit acetaldehyde in proportion to the number of cells in the culture medium. However, studies in another laboratory led to conflicting results, so these SIFT-MS studies have been repeated and extended to include NL20 normal lung epithelial cells and 35FL121 Tel+ telomerase positive lung fibroblast cells. Thus, SIFT-MS has been used to quantify acetaldehyde and, additionally, carbon dioxide, acetone and ethanol in the headspace of the cell culture medium alone and the headspace of the appropriate medium containing 50 x 10(6) or 80 x 10(6) cells following incubation for 16 h at 37 degrees C. Three independent experiments were carried out for each cell type for both cell numbers and for each of the two culture media used. The results showed that acetone and ethanol were only released by the culture medium, specifically from the foetal calf serum contained in the medium, and not by the cells. Acetaldehyde was also released by the medium, but at relatively lower levels than the other three compounds, and was also generated by the CALU-1 and NL20 cell cultures in proportions to the number of cells in the medium. However, following incubation, the acetaldehyde levels in the headspace of the 35FL121 Tel+ cell cultures were much lower than those present in the headspace of the medium alone. Carbon dioxide was clearly generated by the CALU-1 and 35FL121 Tel+ cells indicating that they were respiring normally, but much less was produced by the NL20 cells, presumably indicating that normal metabolism was being inhibited.
31. P. Cap, K. Dryahina, F. Pehal, P. Španěl. "Selected ion flow tube mass spectrometry of exhaled breath condensate headspace." Rapid Communications in Mass Spectrometry 22 (2008) 2844-2850. http://dx.doi.org/10.1002/rcm.3685
Collection of exhaled breath condensate (EBC) is a relatively simple noninvasive method of breath analysis; however, no data have been reported that would relate concentration of volatile compounds in EBC to their gaseous concentrations in exhaled air. The aim of the study was to investigate which volatile compounds are present in EBC and how their concentrations relate to results of direct breath analysis. Thus, samples of EBC were collected in a standard way from several subjects and absolute levels of several common volatile breath metabolites (ammonia, acetone, ethanol, methanol, propanol, isoprene, hydrogen cyanide, formaldehyde and acetaldehyde) were then determined in their headspace using selected ion flow tube mass spectrometry (SIFT-MS). Results are compared with those from on-line breath analyses carried out immediately before collecting the EBC samples. It has been demonstrated that SIFT-MS can be used to quantify the concentrations of volatiles in EBC samples and that, for methanol, ammonia, ethanol and acetone, the EBC concentrations correlate with the direct breath levels. However, the EBC concentrations of isoprene, formaldehyde, acetaldehyde, hydrogen cyanide and propanol do not correlate with direct breath measurements. Copyright (C) 2008 John Wiley & Sons, Ltd.
32. R.N. Bloor, T.S. Wang, P. Španěl, D. Smith. "Ammonia release from heated 'street' cannabis leaf and its potential toxic effects on cannabis users." Addiction 103 (2008) 1671-1677. http://dx.doi.org/10.1111/j.1360-0443.2008.02281.x
Aims To use selected ion flow tube mass spectrometry (SIFT-MS) to analyse the molecular species emitted by heated 'street' cannabis plant material, especially targeting ammonia. Materials and methods Samples of 'street' cannabis leaf, held under a UK Home Office licence, were prepared by finely chopping and mixing the material. The samples were then heated in commercially available devices. The air containing the released gaseous compounds was sampled into the SIFT-MS instrument for analysis. Smoke from standard 3% National Institute on Drug Abuse (NIDA) cannabis cigarettes was also analysed. Findings For 'street' cannabis, ammonia was present in the air samples from the devices at levels approaching 200 parts per million (p.p.m.). This is compared with peak levels of 10 p.p.m. using NIDA samples of known provenance and tetrahydrocannabinol content (3%). Several other compounds were present at lower levels, including acetaldehyde, methanol, acetone, acetic acid and uncharacterized terpenes. Conclusions Awareness of the risks of inhaling the smoke directly from burning cannabis has led to the development of a number of alternative methods of delivery, which are claimed to be safer than direct smoking. Ammonia at toxic levels is produced from heating 'street' cannabis in these commercially available devices. Thus, the use of these devices to deliver 'street' cannabis is now open to question and further research is needed to investigate their safety.
33. J.M. Van Doren, T.M. Miller, A.A. Viggiano, P. Španěl, D. Smith, J.C. Bopp, J. Troe. "Experimental and theoretical investigation of electron attachment to SF5Cl." Journal of Chemical Physics 128 (2008). http://dx.doi.org/10.1063/1.2831767
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.
34. C. Chan, D. Smith, P. Španěl, C.W. McIntyre, S.J. Davies. "A non-invasive, on-line deuterium dilution technique for the measurement of total body water in haemodialysis patients." Nephrology Dialysis Transplantation 23 (2008) 2064-2070. http://dx.doi.org/10.1093/ndt/gfn045
Background. Despite its importance, total body water (TBW) is usually estimated rather than measured due to the complexity of isotope dilution methods. The aim of this study was to demonstrate the applicability in haemodialysis (HD) patients of a recently developed on-line breath test, previously validated in healthy subjects, that uses the gold standard deuterium dilution method to measure TBW. In particular we wished to show that a pre-dialysis estimation was as good as a post-dialysis equilibrated measurement in order to avoid patients needing to remain behind after dialysis treatment. Methods. The dispersal kinetics of breath HDO, measured using a flowing afterglow mass spectrometer (FA-MS) following ingestion of D2O immediately post-dialysis, were determined in 12 haemodialysis patients and used to calculate the absolute TBWPostHD after full equilibration. TBWPreHD was then determined from breath samples taken immediately prior to the next dialysis. This measurement was adjusted for the interdialytic weight change and urine output (TBWPreHD-adjusted) and compared to the TBWPostHD. The accuracy and precision of FA-MS was also assessed using known concentrations of deuterium-enriched water samples. Results. Mean TBWPostHD was 50.0 +/- 9.3 L and TBWPreHD-adjusted was 50.7 +/- 9.0 L. They were highly correlated (R = 0.99, P < 0.001) with a CV of 2.6%. The mean difference was +0.74 L (SEM 0.35, 95% CI -0.03 to 1.51 L, P = 0.059), compatible with a daily insensible loss of 0.37 L. Accuracy and precision of FA-MS were comparable to the previous validation work. Conclusions. This non-invasive adaptation of the D isotope dilution method for determining TBW can be applied to haemodialysis patients who show deuterium equilibration kinetics identical to normal subjects; a pre-dialysis estimation may be used to determine TBW, and so avoiding the necessity to remain behind after dialysis making this suitable for application in the clinical setting.
35. T. Wang, P. Španěl, D. Smith. "Selected ion flow tube mass spectrometry of 3-hydroxybutyric acid, acetone and other ketones in the headspace of aqueous solution and urine." International Journal of Mass Spectrometry 272 (2008) 78-85. http://dx.doi.org/10.1016/j.ijms.2008.01.002
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.
36. I. Kushch, K. Schwarz, L. Schwentner, B. Baumann, A. Dzien, A. Schmid, K. Unterkofler, D. Gastl, P. Španěl, D. Smith, A. Amann. "Compounds enhanced in a mass spectrometric profile of smokers' exhaled breath versus non-smokers as determined in a pilot study using PTR-MS." Journal of Breath Research (2008) 026002. http://dx.doi.org/10.1088/1752-7155/2/2/026002
A pilot study has been carried out to define typical characteristics of the trace gas compounds in exhaled breath of non-smokers and smokers to assist interpretation of breath analysis data from patients who smoke with respiratory diseases and lung cancer. Exhaled breath was analyzed using proton transfer reaction-mass spectrometry (PTR-MS) for 370 volunteers (81 smokers, 210 non-smokers, 79 ex-smokers). Volatile organic compounds corresponding to product ions at seven mass-to-charge ratios (m/z 28, 42, 69, 79, 93, 97, 123) in the PTR-MS spectra differentiated between smokers and non-smokers. The Youden index (= maximum of sensitivity + specificity [?] 1, YI) as a measure for differentiation between smokers and non-smokers was YI = 0.43 for ions at the m/z values 28 (tentatively identified as HCN), YI = 0.75 for m/z = 42 (tentatively identified as acetonitrile) and YI = 0.53 for m/z = 79 (tentatively identified as benzene). No statistically significant difference between smokers and non-smokers was observed for the product ions at m/z = 31 and 33 (compounds tentatively identified as formaldehyde and methanol). When interpreting the exhaled breath of lung cancer or COPD patients, who often smoke, compounds appearing at the above-mentioned seven mass-to-charge ratios should be considered with appropriate care to avoid misdiagnosis. Validation studies in larger numbers of patients with more precise delineation of their smoking behavior and using additional analytical techniques such as GC/MS and SIFT-MS should be carried out.
37. A. Pysanenko, P. Španěl, D. Smith. "A study of sulfur-containing compounds in mouth-and nose-exhaled breath and in the oral cavity." Journal of Breath Research 2 (2008) 046004. http://dx.doi.org/10.1088/1752-7155/2/4/046004
38. D. Smith, T.S. Wang, A. Pysanenko, P. Španěl. "A selected ion flow tube mass spectrometry study of ammonia in mouth- and nose-exhaled breath and in the oral cavity." Rapid Communications in Mass Spectrometry 22 (2008) 783-789. http://dx.doi.org/10.1002/rcm.3434
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.
39. K. Sovova, M. Ferus, I. Matulkova, P. Španěl, K. Dryahina, O. Dvorak, S. Civis. "A study of thermal decomposition and combustion products of disposable polyethylene terephthalate (PET) plastic using high resolution fourier transform infrared spectroscopy, selected ion flow tube mass spectrometry and gas chromatography mass spectrometry." Molecular Physics 106 (2008) 1205-1214. http://dx.doi.org/10.1080/00268970802077876
The industrial production of poly (ethylene terephthalate), PET, continues to increase and thus it is important to understand the composition of fumes resulting from its disposal as a part of incinerated waste. In this study samples of PET material were combusted in a furnace corresponding to the German standard DIN 53,436 at temperatures of 500 degrees C, 800 degrees C (in an air flow) and also uncontrolled combustion in air. The gaseous products were then analysed using three different analytical methods: high resolution Fourier transform infrared spectroscopy (FTIR), selected ion flow tube mass spectrometry (SIFT-MS) and gas chromatography mass spectrometry (GC-MS). Carbon dioxide, methane, ethylene, acetylene, formaldehyde (methanal) and acetaldehyde (ethanal) were detected by FTIR. Water, methane, acetaldehyde, ethylene, formaldehyde, methanol, acetone, benzene, terephthalic acid, styrene (ethenylbenzene), ethanol, toluene (methylbenzene), xylene (dimethylbenzene), ethylbenzene, naphthalene, biphenyl and phenol concentrations were all quantified by both SIFT-MS and GC-MS. Additionally, the fumes resulting from uncontrolled combustion in air were analysed by FTIR which resolves the rotation-vibration structure of the absorption bands of formaldehyde (2779.90 and 2778.48 cm(-1)) and propane, which was identified from characteristic vibrations of CH3 groups at 2977.00 and 2962.00 cm(-1). The spectra were compared with reference standards.
40. P. Španěl, D. Smith. "Quantification of trace levels of the potential cancer biomarkers formaldehyde, acetaldehyde and propanol in breath by SIFT-MS." Journal of Breath Research 2 (2008) 046003. http://dx.doi.org/10.1088/1752-7155/2/4/046003
41. T. Wang, A. Pysanenko, K. Dryahina, P. Španěl, D. Smith. "Analysis of breath, exhaled via the mouth and nose, and the air in the oral cavity." Journal of Breath Research 2 (2008) 037013. http://dx.doi.org/10.1088/1752-7155/2/3/037013
42. C. Turner, B. Parekh, C. Walton, P. Španěl, D. Smith, M. Evans. "An exploratory comparative study of volatile compounds in exhaled breath and emitted by skin using selected ion flow tube mass spectrometry." Rapid Communications in Mass Spectrometry 22 (2008) 526-532. http://dx.doi.org/10.1002/rcm.3402
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.
43. P. Španěl, K. Dryahina, D. Smith. "Microwave plasma ion sources for selected ion flow tube mass spectrometry: Optimizing their performance and detection limits for trace gas analysis." International Journal of Mass Spectrometry 267 (2007) 117-124. http://dx.doi.org/10.1016/j.ijms.2007.02.023
The performance of the ion sources 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 source 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 source 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.
44. C. Chan, S.J. Davies, C. McIntyre, D. Smith, P. Španěl (2007). 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. Nephrology Dialysis Transplantation. 22: 314-314.
45. D. Smith, C. Turner, P. Španěl. "Volatile metabolites in the exhaled breath of healthy volunteers: their levels and distributions." Journal of Breath Research (2007) 014004. http://dx.doi.org/10.1088/1752-7155/1/1/014004
The data obtained for the concentration distributions of the most abundant volatile metabolites in exhaled breath determined in two independent studies are reviewed, the first limited study involving five healthy volunteers providing daily breath samples over a month, and the subsequent study involving 30 healthy volunteers providing breath samples weekly over six months. Both studies were carried out using selected ion flow tube mass spectrometry, SIFT-MS, to obtain on-line, real-time analyses of single breath exhalations, avoiding the complications associated with sample collection. The distributions of the metabolites from the larger more comprehensive study are mostly seen to be log normal with the median values (in parts per billion, ppb) being ammonia (833), acetone (477), methanol (461), ethanol (112), propanol (18), acetaldehyde (22), isoprene (106) with the geometric standard deviation being typically 1.6, except for ethanol which was larger (3.24) due to the obvious increase of breath ethanol following the ingestion of sugar. These were the first well-defined concentration distributions of breath metabolites obtained and they are the essential requirement for recognizing abnormally high levels that are associated with particular diseases. The associations of each metabolite with known diseased states are alluded to. These SIFT-MS studies reveal the promise of breath analysis as a valuable addition to the tools for clinical diagnosis and therapeutic monitoring.
46. P. Španěl, K. Dryahina, D. Smith. "Acetone, ammonia and hydrogen cyanide in exhaled breath of several volunteers aged 4-83 years." Journal of Breath Research 1 (2007) 011001. http://dx.doi.org/10.1088/1752-7155/1/1/011001
Original on-line measurements of acetone, ammonia and hydrogen cyanide in the exhaled breath of several volunteers within the age ranges 4-6 years and 60-83 years are reported and compared with previous data on volunteer cohorts covering ages 17-18 years and 20-60 years. The compiled data show that a significant statistical increase in breath ammonia occurs with increasing age, but that acetone and hydrogen cyanide do not vary greatly with age.
47. P. Španěl, K. Dryahina, D. Smith. "The concentration distributions of some metabolites in the exhaled breath of young adults." Journal of Breath Research 1 (2007) 026001. http://dx.doi.org/10.1088/1752-7155/1/2/026001
The concentrations of ammonia, acetone, methanol, ethanol, propanol and hydrogen cyanide have been measured in the exhaled breath of 26 young adults of age 17/18 years, using selected ion flow tube mass spectrometry (SIFT-MS). Thus the concentration distributions have been constructed and are seen to be essentially log normal with median values in parts per billion (ppb), being ammonia, 317; acetone, 363; methanol, 238; ethanol, 104; propanol, 13; hydrogen cyanide (HCN), 8. There is a clear separation in the median breath ethanol levels between those volunteers who had ingested sugary food/drinks (109 ppb) and those who had not (48 ppb). These data are compared with the results of a study of the same breath compounds, excepting HCN, for a similar sized cohort of healthy volunteers within the age range of 20 to 60 years, which shows that the median levels of these compounds are lower in the young adult volunteer cohort. These HCN measurements are the first to be made in the breath of healthy individuals. The potential implications of these combined results for clinical diagnosis are alluded to.
48. D. Smith, P. Španěl. "The challenge of breath analysis for clinical diagnosis and therapeutic monitoring." Analyst 132 (2007) 390-396. http://dx.doi.org/10.1039/b700542n
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.
49. P. Španěl, D. Smith. "Selected ion flow tube mass spectrometry for on-line trace gas analysis in biology and medicine." European Journal of Mass Spectrometry 13 (2007) 77-82. http://dx.doi.org/10.1255/ejms.843
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.
50. P. Španěl, K. Dryahina, D. Smith. "A general method for the calculation of absolute trace gas concentrations in air and breath from selected ion flow tube mass spectrometry data." International Journal of Mass Spectrometry 249 (2006) 230-239. http://dx.doi.org/10.1016/j.ijms.2005.12.024
A complete description is presented of a numerical method that allows the calculation, in real time, of absolute concentrations of trace gases, including volatile organic compounds and water vapour, from selected ion flow tube mass spectrometry, SIFT-MS, data. No assumptions are made concerning the SIFT-MS instrument size or its configuration and thus the calculation can be applied to the currently available, relatively large instruments and the anticipated new generation of smaller SIFT-MS instruments. This numerical method clearly distinguishes those parameters that are obviously specific to a particular instrument, including flow tube geometry, degree of mass discrimination in the analytical mass spectrometer and flow tube reaction time, from general fundamental processes, in particular the differential diffusive loss of ions along the flow tube that is dependent on the properties of those ions involved in the determination of the concentrations of particular trace gases. The essential reaction and transport kinetics are outlined, which describe the formation and loss of the product ions formed in the chemical ionisation of the trace gases by the precursor ions. A generalised calculation of the required ionic diffusion coefficients is introduced with options either for their accurate determination from the molecular geometry of ions or for less accurate but simpler estimates obtained using just the ionic mass. Based on the above ideas, a straightforward calculation sequence is shown to determine trace gas concentrations by SIFT-MS, and its utility demonstrated by an example of the analysis of acetone in exhaled breath. (c) 2005 Elsevier B.V. All rights reserved.
51. R.N. Bloor, P. Španěl, D. Smith. "Quantification of breath carbon disulphide and acetone following a single dose of disulfiram (Antabuse) using selected ion flow tube mass spectrometry (SIFT-MS)." Addiction Biology 11 (2006) 163-169. http://dx.doi.org/10.1111/j.1355-6215.2006.00015.x
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.
52. D. Smith, T.S. Wang, P. Španěl, R. Bloor. "The increase of breath ammonia induced by niacin ingestion quantified by selected ion flow tube mass spectrometry." Physiological Measurement 27 (2006) 437-444. http://dx.doi.org/10.1088/0967-3334/27/6/001
The ingestion of relatively large doses of the vitamin niacin by healthy volunteers results in a reddening of the skin, a skin 'flush'. Thus, we have carried out a study of the breath metabolites of two healthy volunteers following (i) the ingestion of 200 mg of immediate-release niacin, (ii) as (i) but preceded by the ingestion of 325 mg of aspirin that diminishes the skin 'flush', (iii) ingestion of 500 mg of slow-release niacin. On-line breath analysis was carried out using selected ion flow tube mass spectrometry, SIFT-MS. The interesting new observation is that the breath ammonia levels of both volunteers clearly increased following (i) and (ii), and an obvious skin flush did occur following (i) but not following (ii). The slow-release niacin (iii) did not result in a flush and the breath ammonia levels increased more slowly and did not reach the higher levels produced by (i) and (ii). The results of these experiments demonstrate that breath ammonia levels are dependent on the blood/plasma levels of niacin, but are not directly related to the flushing phenomenon, and that the observed increases in blood/breath ammonia levels are consistent with current knowledge of the metabolic pathways of niacin. The parallel measurements of breath isoprene are presented, which demonstrate the quality of breath analyses that can be achieved using SIFT-MS.
53. C. Chan, D. Smith, P. Španěl, C. McIntyre, S. Davies (2006). Deuterium kinetics in haemodialysis patients and the optimal time schedule for breath sampling in the determination of total body water (TBW) using flowing afterglow mass spectrometry (FAMS). Nephrology Dialysis Transplantation. 21: 422-422.
54. D. Smith, K.M.K. Ismail, A.M. Diskin, G. Chapman, J.L. Magnay, P. Španěl, S. O'Brien. "Increase of acetone emitted by urine in relation to ovulation." Acta Obstetricia Et Gynecologica Scandinavica 85 (2006) 1008-1011. http://dx.doi.org/10.1080/00016340600590535
Background. Selected ion flow tube mass spectrometry allows trace gas quantification in exhaled breath and in the air/vapor above liquids (headspace) down to the 10 parts-per-billion level. During selected ion flow tube mass spectrometry investigation of the volatile compounds emitted by urine, high acetone levels were incidentally identified in the headspace of urine from healthy female volunteers around their mid-cycle. Hence, this study was designed to measure urine headspace acetone levels throughout the menstrual cycle. Methods. Using selected ion flow tube mass spectrometry we measured daily urine headspace acetone concentrations of seven ovulating (group 1) and three postmenopausal volunteers (group 2). Results. A several-fold increase in urine headspace acetone level was detected 2-3 days after the predicted day of ovulation in 5 of the 7 volunteers in group 1. No such rise was detected in group 2. Conclusion. This study provides the basis for future research to understand the reason for and the potential utility of this phenomenon.
55. C. Turner, P. Španěl, D. Smith. "A longitudinal study of methanol in the exhaled breath of 30 healthy volunteers using selected ion flow tube mass spectrometry, SIFT-MS." Physiological Measurement 27 (2006) 637-648. http://dx.doi.org/10.1088/0967-3334/27/7/007
Selected ion flow tube mass spectrometry, SIFT-MS, has been used to monitor the volatile compounds in the exhaled breath of 30 volunteers (19 male, 11 female) over a six-month period. Volunteers provided breath samples each week between 8:45 am and 1 pm (before lunch), and the concentrations of several trace compounds were obtained. In this paper the focus is on methanol in breath. The median methanol level determined using the H3O+ precursor ions for all samples was 461 parts-per-billion (ppb), the concentrations for all the samples ranging from 32 to 1684 ppb. The distribution of breath methanol concentration is seen to be log-normal for this healthy population; the geometric mean was 450 ppb, close to the median value, and the multiplicative (geometric) standard deviation was 1.62. Breath methanol is not correlated with age, breath ethanol or ethanol consumed in the previous 24 h, but there was an inverse correlation with body mass index (BMI) for the cohort of volunteers recruited for this study. Observed breath methanol levels are well compatible with the previously published blood methanol levels. Some tentative suggestions are made concerning the origin of endogenous methanol.
56. C. Turner, P. Španěl, D. Smith. "A longitudinal study of breath isoprene in healthy volunteers using selected ion flow tube mass spectrometry (SIFT-MS)." Physiological Measurement 27 (2006) 13-22. http://dx.doi.org/10.1088/0967-3334/27/1/002
Thirty volunteers (19 males, I I females) were recruited for a 6-month study of the volatile compounds in their exhaled breath using the selected ion flow tube mass spectrometry (SIFT-MS) analytical technique. Volunteers provided weekly breath samples between 8:45 am and I pm (before lunch), and the concentrations of several trace compounds were obtained. In this paper, we focus on the isoprene in alveolar breath, which was monitored by SIFT-MS using NO+ precursor ions. The mean isoprene level for all samples was 118 parts per billion (ppb) with a standard deviation of 68 ppb and the range of values for breath samples given is 0-474 ppb. Variability in isoprene levels was similar in most volunteers. Isoprene levels increased immediately after moderate exercise, but returned to normal within 2-3 min for those few volunteers that were investigated. Cholesterol levels analysed for only three of the subjects were not obviously correlated with isoprene concentration in breath. Differences in isoprene levels were not directly correlated to gender, age or body mass index.
57. P. Španěl, C. Turner, T.S. Wang, R. Bloor, D. Smith. "Generation of volatile compounds on mouth exposure to urea and sucrose: implications for exhaled breath analysis." Physiological Measurement 27 (2006) N7-N17. http://dx.doi.org/10.1088/0967-3334/27/2/n01
The increase in ammonia and ethanol in the exhaled breath stream following mouthwashes by aqueous solutions of urea and sugar (sucrose), respectively, has been investigated by analysing exhaled breath in real time using selected ion flow tube mass spectrometry, SIFT-MS. It is shown that the measured levels of these compounds in the stream of exhaled breath can be much greater than the endogenous levels originating at the alveolar boundary. Thus, it is concluded that without careful preparation, mouth production of these compounds, and other compounds as yet unidentified, can seriously compromise the quantification of truly endogenous trace compounds present in blood and in the alveolar breath, as required for clinical diagnosis, and can probably introduce additional compounds into the breath stream that could seriously mislead breath analysis. The concentrations of both the urea and sucrose solutions used to enhance the ammonia and ethanol levels were larger than normally present in food and drinks and so in most situations such severe enhancements will not occur.
58. J. Julak, E. Stranska, V. Rosova, H. Geppert, P. Španěl, D. Smith. "Bronchoalveolar lavage examined by solid phase microextraction, gas chromatography-mass spectrometry and selected ion flow tube mass spectrometry." Journal of Microbiological Methods 65 (2006) 76-86. http://dx.doi.org/10.1016/j.mimet.2005.06.009
Samples (210 in total) of broncholaveolar lavages (BALs), obtained from patients hospitalized with pneumonia in various departments of two hospitals, were analysed using the method of solid phase microextraction-gas chromatography (SPME-GC) with FID detection. Up to 20% (9% unequivocally, 11% probably) of these samples was found to contain volatile fatty acids (VFAs) in the series from acetic acid to heptanoic acid. Importantly, the presence of these acids indicates the presence of fermenting anaerobic bacteria, which were not detected by the conventional microbiological examination. Other compounds, namely the heptanol and cyclohexanone, were also detected by this method in some samples. Cyclohexanone occurred almost exclusively in samples from patients receiving intensive care with mechanical ventilation, and is suspected to originate from plastic parts of ventilators. Selected representative samples were also analysed using further methods, namely gas chromatography-mass spectrometry (GC-MS) of native and silylated samples, and selected ion flow tube mass spectrometry (SIFT-MS). These methods confirmed the identities of above mentioned compounds, and detected numerous other compounds tentatively identified as various alcohols, aldehydes, ketones, esters and hydrogen cyanide, HCN. Most of these compounds occurred in small amounts and their origin and diagnostic significance remains uncertain, except, that is, for the HCN, which indicates the presence of Pseudomonas aeruginosa. (c) 2005 Elsevier B.V All rights reserved.
59. C. Turner, P. Španěl, D. Smith. "A longitudinal study of ammonia, acetone and propanol in the exhaled breath of 30 subjects using selected ion flow tube mass spectrometry, SIFT-MS." Physiological Measurement 27 (2006) 321-337. http://dx.doi.org/10.1088/0967-3334/27/4/001
60. C. Turner, P. Španěl, D. Smith. "A longitudinal study of ethanol and acetaldehyde in the exhaled breath of healthy volunteers using selected-ion flow-tube mass spectrometry." Rapid Communications in Mass Spectrometry 20 (2006) 61-68. http://dx.doi.org/10.1002/rcm.2275
Selected-ion flow-tube mass spectrometry (SIFT-MS) has been used to monitor the volatile compounds in the exhaled breath of 30 volunteers (19 male, 11 female) over a 6-month period. Volunteers provided breath samples each week between 8:45 and 13:00 (before lunch), and the concentrations of several trace compounds were obtained. In this paper the focus is on ethanol and acetaldehyde, which were simultaneously quantified by SIFT-MS using H3O+ precursor ions. The mean ethanol level for all samples was 196 parts-per-billion (ppb) with a standard deviation of 244ppb, and the range of values for breath samples analysed is 0 to 1663ppb. The mean acetaldehyde level for all samples was 24 ppb with a standard deviation of 17 ppb, and the range of values for breath samples analysed is 0 to 104 ppb. Background (ambient air) levels of ethanol were around 50ppb, whereas any background acetaldehyde was usually undetectable. Increased ethanol levels were observed if sweet drink/food had been consumed within the 2h prior to providing the breath samples, but no increase was apparent when alcohol had been consumed the previous evening. The measured endogenous breath ethanol and acetaldehyde levels were not correlated. These data relating to healthy individuals are a prelude to using breath analysis for clinical diagnosis, for example, the recognition of bacterial overload in the gut (ethanol) or the possibly of detecting tumours in the body (acetaldehyde). Copyright (c) 2005 John Wiley & Sons, Ltd.
61. J. Kubista, P. Španěl, K. Dryahina, C. Workman, D. Smith. "Combined use of gas chromatography and selected ion flow tube mass spectrometry for absolute trace gas quantification." Rapid Communications in Mass Spectrometry 20 (2006) 563-567. http://dx.doi.org/10.1002/rcm.2340
The value of the gas chromatography (GC) and selected ion flow tube mass spectrometry (SIFT-MS) combination for the analysis of trace gases is demonstrated by the quantification of acetone in air samples using the three precursor ions available to SIFT-MS, viz. H3O+, NO+ and O-2(+), and by the separation of the isomers 1-propanol and 2-propanol, and their analysis using H3O+ precursor ions. It is shown that the GC/SIFT-MS combination allows for accurate trace gas quantification obviating the regular, time-consuming calibrations that are usually required for the more commonly used detectors of GC systems, and the positive identification of isomers in mixtures that is often challenging using SIFT-MS alone. Thus, the GC/SIFT-MS combination paves the way to more confident analyses of complex mixtures such as exhaled breath. Copyright (c) 2006 John Wiley & Sons, Ltd.