A. Jordan

ON-LINE MONITORING OF VOLATILE ORGANIC COMPOUNDS AT PPTV LEVELS BY MEANS OF PROTON-TRANSFER-REACTION MASS SPECTROMETRY (PTR-MS) MEDICAL APPLICATIONS, FOOD CONTROL AND ENVIRONMENTAL RESEARCH

Abstract A proton transfer reaction mass spectrometer (PTR-MS) system has been developed which allows for on-line measurements of trace components with concentrations as low as a few pptv. The method is based on reactions of H 3 O + ions, which perform non-dissociative proton transfer to most of the common volatile organic compounds (VOCs) but do not react with any of the components present in clean air. Medical applications by means of breath analysis allow for monitoring of metabolic processes in the human body, and examples of food research are discussed on the basis of VOC emissions from fruit, coffee and meat. Environmental applications include investigations of VOC emissions from decaying biomatter which have been found to be an important source for tropospheric acetone, methanol and ethanol. On-line monitoring of the diurnal variations of VOCs in the troposphere yield data demonstrating the present sensitivity of PTR-MS to be in the range of a few pptv. Finally, PTR-MS has proven to be an ideal tool to measure Henrys law constants and their dependencies on temperature as well as on the salt content of water.

Proton transfer reaction mass spectrometry: on-line trace gas analysis at the ppb level

Abstract A system for trace gas analysis using proton transfer reaction mass spectrometry (PTR-MS) has been developed which allows for on-line measurements of components with concentrations as low as 1 ppb. The method is based on reactions of H 3 O + ions, which perform non-dissociative proton transfer to most of the common organic trace constituents but do not react with any of the components present in clean air. Examples of analysis of breath taken from smokers and non-smokers as well as from patients suffering from cirrhosis of the liver, and of air in buildings as well as of ambient air taken at a road crossing demonstrate the wide range of applicability of this method. An enhanced level of acetonitrile in the breath is a most suitable indicator that a person is a smoker. Enhanced levels of propanol strongly indicate that a person has a severe liver deficiency.

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

Airborne measurements of volatile organic compounds (VOC) were performed overthe tropical rainforest in Surinam (0–12 km altitude,2°–7° N, 54°–58° W) using the proton transferreaction mass spectrometry (PTR-MS) technique, which allows online monitoringof compounds like isoprene, its oxidation products methyl vinyl ketone,methacrolein, tentatively identified hydroxy-isoprene-hydroperoxides, andseveral other organic compounds. Isoprene volume mixing ratios (VMR) variedfrom below the detection limit at the highest altitudes to about 7 nmol/molin the planetary boundary layer shortly before sunset. Correlations betweenisoprene and its product compounds were made for different times of day andaltitudes, with the isoprene-hydroperoxides showing the highest correlation.Model calculated mixing ratios of the isoprene oxidation products using adetailed hydrocarbon oxidation mechanism, as well as the intercomparisonmeasurement with air samples collected during the flights in canisters andlater analysed with a GC-FID, showed good agreement with the PTR-MSmeasurements, in particular at the higher mixing ratios.Low OH concentrations in the range of 1–3 × 105molecules cm-3 averaged over 24 hours were calculated due to lossof OH and HO2 in the isoprene oxidation chain, thereby stronglyenhancing the lifetime of gases in the forest boundary layer.

Acetonitrile and benzene in the breath of smokers and non-smokers investigated by proton transfer reaction mass spectrometry (PTR-MS)

Abstract Benzene and acetonitrile are both present in greater concentrations in the breath of smokers than in non-smokers. The concentrations of these neutrals can be readily detected in the gas phase by their proton transfer reactions with H3O+. The concentration of benzene in the breath of smokers rapidly decreases with the time since the last cigarette was smoked, declining to values similar to those of non-smokers within an hour. In contrast, the concentration of acetonitrile in the breath of smokers takes nearly a week to decrease to that of non-somokers, once smoking stops. Thus the analysis of acetonitrile in the breath is a most suitable indicator of whether a given subject is or is not a smoker.

PROTON TRANSFER REACTION MASS SPECTROMETRY (PTR-MS) : PROPANOL IN HUMAN BREATH

Abstract Proton transfer reaction mass spectrometry (PTR-MS) based on reactions of H 3 O + ions has been used to measure the concentrations of propanol in 46 healthy persons, yielding an average concentration of about 150 ppb. That the measurements were not obscured by other components of the same mass as propanol was proven by comparison of PTR-MS data with separate selected-ion flow-drift tube (SIFDT) investigations of the energy dependences of reactions of H 3 O + and H 3 O + ·H 2 O with isopropanol, n -propanol, acetic acid and methyl formate.

High acetone concentrations throughout the 0-12 km altitude range over the tropical rainforest in Surinam

Airborne measurements of acetone were performed overthe tropical rainforest in Surinam(2°–7° N, 54°–58° W, 0–12 kmaltitude) during the LBA-CLAIRE campaign in March1998, using a novel proton transfer reaction massspectrometer (PTR-MS) that enables the on-linemonitoring of volatile organic compounds (VOC) with ahigher proton affinity than water. The measuredacetone volume mixing ratios ranged from ∼0.1 nmol/molup to ∼8 nmol/mol with an overall average of 2.6nmol/mol and a standard deviation of 1.0 nmol/mol. Theobserved altitude profile and correlations with CO,acetonitrile, propane and wind direction are discussedwith respect to potential acetone sources. No linearcorrelation between acetone and CO mixing ratios wasobserved, at variance with results of previousmeasurement campaigns. The mean acetone/CO ratio(0.022) was substantially higher than typical valuesfound before. The abundance of acetone appears to beinfluenced, but not dominated, by biomass burning,thus suggesting large emissions of acetone and/oracetone precursors, such as possibly 2-propanol, fromliving plants or decaying litter in the rainforest.

PTR-MS real time monitoring of the emission of volatile organic compounds during postharvest aging of berryfruit

Abstract A novel method, based on proton transfer reaction-mass spectrometry (PTR-MS) was used to monitor the postharvest aging of strawberries, blackberries, raspberries, blueberries, and white and red currants by real time detection of volatile organic compounds (VOCs) in the headspace of the fruits. The observed intensities of emission for the different identified compounds, and their ratios as well as their rate of evolution, showed definite, berry-specific, behaviour. Very high sensitivity (sub-ppb level) combined with real time detection of a large variety of compounds makes PTR-MS very promising for studies dealing with quality assessment and preservation of fruits.

High concentrations of reactive biogenic VOCs at a high altitude site in late autumn

Volatile organic compounds (VOCs) at the Sonnblick Observatory, Austria (3106 m a.s.l.) were measured in autumn 1999 using proton-transfer-reaction mass spectrometry (PTR-MS). Anthropogenic VOCs at this remote site, such as benzene and toluene (50 pptv to 2 ppbv), were primarily traced to air from urban areas. In mid-November, following a hard freeze in the central Alps, a different pattern of VOCs developed similar to that seen with C5 and C6 leaf wound compounds (0.5 to 5 ppbv range). The common origins of these compounds are proposed to be freeze-damaged leaves, inferred from laboratory investigations that identified hexenals, hexanal, methylbutanals, pentenol and pentenone formation in such leaves. We suggest that deciduous forests can release large amounts of reactive VOCs during the autumn, and that these releases may be important for regional tropospheric chemistry.

Proton-transfer-reaction mass spectrometry (PTR-MS): on-line monitoring of volatile organic compounds at volume mixing ratios of a few pptv

A system for on-line measurements of trace compounds in air with concentrations as low as a few pptv has been developed on the basis of proton transfer reactions. The sensitivity of this system is demonstrated by means of calibration data of benzene and data on the diurnal variation of C9-alkylbenzene and its 13C-isotope in ambient air. First on-line data on the concentrations of volatile organic compounds obtained during plane flights are presented.

Quantification of passive smoking using proton-transfer-reaction mass spectrometry

Abstract Using acetonitrile as the lead component, quantitative comparison between passive smoking and direct smoking was achieved by performing measurements using proton-transfer-reaction mass spectrometry. Staying for a working day (8 h) in a smoke laden environment, as is typical for pubs where guests are smoking heavily, is equivalent to smoking one to two cigarettes.