[Poeschl2001] "High acetone concentrations throughout the 0–12 km altitude range over the tropical rainforest in Surinam",
Journal of atmospheric chemistry
, vol. 38, no. 2: Springer, pp. 115–132, 2001.
[Karl2001] "Human breath isoprene and its relation to blood cholesterol levels: new measurements and modeling",
Journal of Applied Physiology
, vol. 91, no. 2, pp. 762-770, 2001.
Numerous publications have described measurements of breath isoprene in humans, and there has been a hope that breath isoprene analyses could be a noninvasive diagnostic tool to assess blood cholesterol levels or cholesterol synthesis rate. However, significant analytic problems in breath isoprene analysis and variability in isoprene levels with age, exercise, diet, etc., have limited the usefulness of these measurements. Here, we have applied proton transfer reaction-mass spectrometry to this problem, allowing on-line detection of breath isoprene. We show that breath isoprene concentration increases within a few seconds after exercise is started as a result of a rapid increase in heart rate and then reaches a lower steady state when breath rate stabilizes. Additional experiments demonstrated that increases in heart rate associated with standing after reclining or sleeping are associated with increased breath isoprene concentrations. An isoprene gas-exchange model was developed and shows excellent fit to breath isoprene levels measured during exercise. In a preliminary experiment, we demonstrated that atorvastatin therapy leads to a decrease in serum cholesterol and low-density-lipoprotein levels and a parallel decrease in breath isoprene levels. This work suggests that there is constant endogenous production of isoprene during the day and night and reaffirms the possibility that breath isoprene can be a noninvasive marker of cholesterologenesis if care is taken to measure breath isoprene under standard conditions at constant heart rate.
[Lelieveld2001] "The Indian Ocean experiment: widespread air pollution from South and Southeast Asia",
, vol. 291, no. 5506: American Association for the Advancement of Science, pp. 1031–1036, 2001.
The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6°S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere.
[Stroud2001] "Isoprene and its oxidation products, methacrolein and methylvinyl ketone, at an urban forested site during the 1999 Southern Oxidants Study",
Journal of Geophysical Research: Atmospheres (1984–2012)
, vol. 106, no. D8: Wiley Online Library, pp. 8035–8046, 2001.
[Warneke2001a] "Isoprene and its oxidation products methyl vinyl ketone, methacrolein, and isoprene related peroxides measured online over the tropical rain forest of Surinam in March 1998",
Journal of Atmospheric Chemistry
, vol. 38, no. 2: Springer, pp. 167–185, 2001.
[Wisthaler2001] "Measurements of acetone and other gas phase product yields from the OH-initiated oxidation of terpenes by proton-transfer-reaction mass spectrometry (PTR-MS)",
, vol. 35, no. 35: Elsevier, pp. 6181–6191, 2001.
The atmospheric oxidation of several terpenes appears to be a potentially relevant source of acetone in the atmosphere. Proton-transfer-reaction mass spectrometry was used as an on-line analytical method in a chamber study to measure acetone and other gas phase products from the oxidation of α- and β-pinene initiated by OH radicals in air and in the presence of NOx. Acetone may be formed promptly, following attack by the OH radical on the terpene, via a series of highly unstable radical intermediates. It can also be formed by slower processes, via degradation of stable non-radical intermediates such as pinonaldehyde and nopinone. Primary acetone and pinonaldehyde molar yields of 11±2% (one σ) and 34±9% (one σ), respectively, were found from the reaction between α-pinene and the OH radical. After all α-pinene had been consumed, an additional formation of acetone due to the degradation of stable non-radical intermediates was observed. The total amount of acetone formed was 15±2% (one σ) of the reacted α-pinene. An upper limit of 12±3% (one σ) for the acetone molar yield from the oxidation of pinonaldehyde was established. From the reaction between β-pinene and the OH radicals, primary acetone and nopinone molar yields of 13±2% (one σ) and 25±3% (one σ), respectively, were observed. Additional amounts of acetone were formed by the further degradation of the primary product, such as the most abundant product nopinone. The total amount of acetone formed was 16±2% (one σ) of the reacted β-pinene. An upper limit of 12±2% (one σ) for the acetone molar yield from the oxidation of nopinone was established. The observed product yields from α- and β-pinene are in good agreement with other studies using mass-spectrometric and gas chromatographic analytical techniques, but differ significantly from previous studies using spectroscopic methods. Possible reasons for the discrepancies are discussed.
[Warneke2001] "Measurements of benzene and toluene in ambient air using proton-transfer-reaction mass spectrometry: calibration, humidity dependence, and field intercomparison",
International Journal of Mass Spectrometry
, vol. 207, no. 3: Elsevier, pp. 167–182, 2001.
[Holzinger2001] "Methanol measurements in the lower troposphere near Innsbruck (047Â° 16 N; 011Â° 24 E), Austria",
, vol. 35, no. 14: Elsevier, pp. 2525–2532, 2001.
[Laat2001] "Model analysis of trace gas measurements and pollution impact during INDOEX",
Journal of Geophysical Research: Atmospheres (1984–2012)
, vol. 106, no. D22: Wiley Online Library, pp. 28469–28480, 2001.
An analysis of acetone (CH3COCH3) and acetonitrile (CH3CN) measurements, performed during the Indian Ocean Experiment (INDOEX), using a chemistry general circulation model is presented. A comparison with measurements indicates that the model simulates realistic CO and acetone distributions, except toward the Indian west coast near the surface. The latter may be related to a sea breeze circulation at the Indian west coast, which is not resolved by the model. A comparison of the measured and modeled correlation between CO and acetone indicates the presence of a background marine acetone source. A model sensitivity study suggests a global marine emission strength of 15-20 Tg acetone yr-1, which is a significant contribution to the estimated global acetone source of 56 (37-80) Tg acetone yr-1. The comparison of measured and modeled CO-acetonitrile correlation from surface measurements indicates that a model sink of acetonitrile in the marine boundary layer is missing. A model sensitivity study suggests that this could be dry deposition (deposition velocity estimate: 0.01-0.05 cms-1) on the ocean surface. A comparison of measured and modeled tropospheric acetonitrile indicates that the model overestimates the free tropospheric acetonitrile mixing ratios up to a factor of 3, which points to a missing free tropospheric sink of acetonitrile in the model. A possible explanation may be stratospheric loss and subsequent stratosphere-troposphere exchange, which was not included in the model.
[Gasperi2001] "The mozzarella cheese flavour profile: a comparison between judge panel analysis and proton transfer reaction mass spectrometry",
Journal of the Science of Food and Agriculture
, vol. 81, no. 3: Wiley Online Library, pp. 357–363, 2001.
[Fay2001] "Novel mass spectrometry methods in flavour analysis",
CHIMIA International Journal for Chemistry
, vol. 55, no. 5: Swiss Chemical Society, pp. 429–434, 2001.
Flavour research is a demanding domain in terms of analytical methodology as key odorants usually occur in trace amounts, often embedded in extracts containing volatile compounds at much higher concentrations. Since its early days, GC-MS has been a key tool in flavour laboratories enabling characterisation of thousands of volatile components in food products. However, as flavour chemists delve deeper into the understanding of flavour generation and delivery, there is a need for more powerful methodologies adapted to their specific needs. This paper will present two techniques that allow flavour separation and characterisation, namely GC-TOFMS and MS/MS. Moreover, APCI-MS, PTR-MS and REMPI-TOFMS will be discussed as they enable direct investigation of volatile compounds without any chromatographic step, thus studying release of flavour compounds during food processing or food consumption.
[Buettner2001] "Observation of the swallowing process by application of videofluoroscopy and real-time magnetic resonance imaging�consequences for retronasal aroma stimulation",
, vol. 26, no. 9: Oxford Univ Press, pp. 1211–1219, 2001.
The process of eating and drinking was observed in vivo by application of videofluoroscopy, a dynamic X-ray technique, as well as real-time magnetic resonance imaging. The study was aimed at elucidating the timing and performance of the physiological organs involved in mastication and swallowing, mainly the tongue, the pharynx and the soft palate (velum palatinum). It was shown for the first time that effective physiological barriers do exist during food consumption that are capable of retaining volatiles such as helium within the oral cavity. These barriers allow the access of odorants to the nasal cavity only at certain times during the eating process. Their effectiveness is related to the texture of the food as well as the amount of food material present in the oral cavity and, thereby, directly influences retronasal aroma perception.
[Warneke2001b] "Organic trace gas composition of the marine boundary layer over the northwest Indian Ocean in April 2000",
, vol. 35, no. 34: Elsevier, pp. 5923–5933, 2001.
[Andreae2001] "Transport of biomass burning smoke to the upper troposphere by deep convection in the equatorial region",
Geophysical Research Letters
, vol. 28, no. 6: Wiley Online Library, pp. 951–954, 2001.
[Karl2001b] "Variability-lifetime relationship of VOCs observed at the Sonnblick Observatory 1999�Estimation of HO-densities",
, vol. 35, no. 31: Elsevier, pp. 5287–5300, 2001.
An extensive dataset of VOC measurements was collected at the Sonnblick Observatory, Austria (3106 m) in Fall/Winter 1999/2000, showing high mixing ratios of anthropogenic and biogenic VOCs at this high altitude site due to upward mixing of air masses (Geophys. Res. Lett. 2F (2001) 507). Here we give an interpretation of proton-transfer-reaction (PTR-MS) mass scans obtained in November 1999 based on fragmentation data, GC-PTR-MS analysis and the variability-lifetime relationship, described by the power law, σ(ln(x))=Aτ−b. The variability-lifetime plot of anthropogenic VOCs gave a proportionality factor A of 1.40 and a,b exponent (sink term) of 0.44 and allowed an estimate of average HO-densities on the order of (1.5±0.4)×105 molecules cm−3. Additionally we were able to indirectly determine a diurnal HO-profile with peak values of (1.3±0.5)×106 molecules cm−3 around midday. HO-reaction rate coefficients for higher aldehydes (heptanal to nonanal) were estimated due to photochemical losses during a stagnant air episode (27 November) and from the variability-lifetime relationship. Combining long term PTR-MS analysis of VOCs and the variability-lifetime method provides a valuable tool for assessing the dominant cause of the variability in VOC concentrations. This information is essential in understanding the sources and photochemical processing of VOCs detected in ambient air at field measurement sites.
[Holzinger2000] "Emissions of volatile organic compounds from Quercus ilex L. measured by proton transfer reaction mass spectrometry under different environmental conditions",
Journal of Geophysical Research
, vol. 105, no. D16, pp. 20573–20579, 2000.
[Crutzen2000] "High spatial and temporal resolution measurements of primary organics and their oxidation products over the tropical forests of Surinam",
, vol. 34, no. 8: Elsevier, pp. 1161–1165, 2000.
Tropical forests with emissions greater than 1015 g C of reactive hydrocarbons per year strongly affect atmospheric chemistry. Here we report aircraft-borne measurements of organics during March 1998 in Surinam, a largely unpolluted region which is optimally located to study chemical processes induced by tropical forest emissions. Isoprene and its degradation products methylvinyl ketone (MVK) and methacrolein (MACR) and possibly isoprene hydroperoxides (ISOHP), were measured in the nmol mol−1 volume mixing ratio (VMR) range, consistent with estimated emissions and model calculations. In addition, high VMRs of some non-isoprene-derived organics were measured, such as acetone (≈2–4 nmol mol1 up to 12 km altitude), an important source of HO and HO2 in the upper troposphere. Moreover, several masses were measured at significant mixing ratios which could not be identified by reference to previous field measurements or gas-phase isoprene chemistry. High VMRs, almost 0.4 nmol mol−1, were also recorded for a compound which is most likely dimethyl sulphide (DMS). If so, boundary layer loss of HO by reactions with hydrocarbons and their oxidation products strongly prolongs the lifetime of DMS, allowing its transport deep into the Amazon forest south of the intertropical convergence zone (ITCZ). We postulate greater sulphate production and deposition north than south of the (ITCZ) with possible consequences for cloud and ecosystem properties.
[Hansel2000] "A method for real-time detection of PAN, PPN and MPAN in ambient air",
Geophysical research letters
, vol. 27, no. 6: Wiley Online Library, pp. 895–898, 2000.
[Yeretzian2000] "On-line monitoring of coffee roasting by proton-transfer-reaction mass-spectrometry",
ACS Symposium Series
, vol. 763: ACS Publications, pp. 112–125, 2000.
[Boschetti2000] "Proton transfer reaction mass spectrometry: a new technique to assess post harvest quality of strawberries",
IV International Strawberry Symposium 567
, pp. 739–742, 2000.
[DeGouw2000] "Proton-transfer chemical-ionization mass spectrometry allows real-time analysis of volatile organic compounds released from cutting and drying of crops",
Environmental science & technology
, vol. 34, no. 12: ACS Publications, pp. 2640–2648, 2000.
The wounding and drying of plant material during crop harvest could be a significant source of volatile organic compounds (VOCs) that enter the atmosphere. Here, we show that these primarily oxygenated VOCs can be measured using proton-transfer chemical-ionization mass spectrometry (PT-CIMS), a method that allows online and simultaneous monitoring of oxygenated VOC levels. For clover, alfalfa, and corn, leaf wounding and in particular drying were shown to lead to strongly enhanced emissions of a series of C6 aldehydes, alcohols, and esters derived from (Z)-3-hexenal. Additionally, for the forage crops clover and alfalfa, enhanced emissions of methanol, acetaldehyde, acetone, and butanone were observed. The identities of the measured carbonyl compounds were confirmed using high-pressure liquid chromatography. For clover, initial cutting led to a VOC release of about 175 μg of C (g dry wt)-1, while during drying the cut clover released >1000 μg of C (g dry wt)-1; qualitatively, similar amounts of VOCs were released from alfalfa, the major hay crop in the United States. The atmospheric implications of these findings may include effects on the local air quality in agricultural areas, contributions to long-range transport of pollutants, and effects on the formation of HOx (=OH + HO2) radicals in the upper troposphere.
[Yeretzian2000a] "Time-resolved headspace analysis by proton-transfer-reaction mass-spectrometry",
ACS Symposium Series
, vol. 763: ACS Publications, pp. 58–72, 2000.
A recently developed technique, Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS), is reviewed based on applications on coffee. PTR-MS is a sensitive and fast method for on-line trace gas analysis. It consists of a specially designed chemical ionization cell, where headspace gas is continuously introduced and volatile organic compounds ionized by proton-transfer from H3O+. Protonated compounds are then mass analyzed in a quadrupole mass filter. First a description of the method will be given, with emphasis on the ionization mechanism. We then discuss a series of experiments that allow mass spectral intensities to be related to chemical compounds. Finally, two applications on coffee are discussed.
[Warneke1999] "Acetone, methanol, and other partially oxidized volatile organic emissions from dead plant matter by abiological processes: Significance for atmospheric HOx chemistry",
Global Biogeochem. Cycles
, vol. 13, no. 1, pp. 9–17, 1999.
[Prazeller1999] "Acetonitril als Biomarker zur Quantifizierung des Passivrauchens",
Ber. nat-med. Verein Innsbruck
, vol. 86: Ber. nat-.med. Verein Innsbruck, pp. 13-19, 1999.
[Holzinger1999] "Biomass burning as a source of formaldehyde, acetaldehyde, methanol, acetone, acetonitrile, and hydrogen cyanide",
Geophysical Research Letters
, vol. 26, no. 8: Wiley Online Library, pp. 1161–1164, 1999.