Human breath analysis: methods for sample collection and reduction of localized background effects

Solid-phase microextraction (SPME) was applied, in conjunction with gas chromatography–mass spectrometry, to the analysis of volatile organic compounds (VOCs) in human breath samples without requiring exhaled breath condensate collection. A new procedure, exhaled breath vapor (EBV) collection, involving the active sampling and preconcentration of a breath sample with a SPME fiber fitted inside a modified commercial breath-collection device, the RTube™, is described. Immediately after sample collection, compounds are desorbed from the SPME fiber at 250 °C in the GC-MS injector. Experiments were performed using EBV collected at −80 °C and at room temperature, and the results compared to the traditional method of collecting exhaled breath condensate at −80 °C followed by passive SPME sampling of the collected condensate. Methods are compared in terms of portability, ease-of-use, speed of analysis, and detection limits. The need for a clean air supply for the study subjects is demonstrated using several localized sources of VOC contaminants including nail polish, lemonade, and gasoline. Various simple methods to supply clean inhaled air to a subject are presented. Chemical exposures are used to demonstrate the importance of providing cleaned air (organic vapor respirator) or an external air source (tubing stretched to a separate room). These techniques allow for facile data interpretation by minimizing background contaminants. It is demonstrated herein that this active SPME breath-sampling device provides advantages in the forms of faster sample collection and data analysis, apparatus portability and avoidance of power or cooling requirements, and performance for sample collection in a contaminated environment.      

Sampling and sample-preparation strategies based on solid-phase microextraction for analysis of indoor air

Applications of solid-phase microextraction (SPME) to the sampling and analysis of volatile organic compounds in indoor air are reviewed, including a summary of quantification methods, coatings, compounds, concentrations, sampling locations and times, and detection limits. Strategies for on-site and off-site sampling and analysis, advantages and challenges associated with SPME for air sampling are discussed.     

Direct, rapid quantitative analyses of BVOCs using SIFT-MS and PTR-MS obviating sample collection

The purpose of this short review is to describe the origins and the principles of operation of selected-ion flow-tube mass spectrometry (SIFT-MS) and proton-transfer-reaction mass spectrometry (PTR-MS), and their application to the analysis of biogenic volatile organic compounds (BVOCs) in ambient air, the humid air (headspace) above biological samples, and other samples. We briefly review the ion chemistry that underpins these analytical methods, which allows accurate analyses. We pay attention to the inherently uncomplicated sampling methodologies that allow on-line, real-time analyses, obviating sample collection into bags or onto traps, which can compromise samples.Whilst these techniques have been applied successfully to the analysis of a wide variety of media, we give just a few examples of data, including for the analysis of BVOCs that are present in tropospheric air and those emitted by plants, in exhaled breath and in the headspace above cell and bacterial cultures (which assist clinical diagnosis and therapeutic monitoring), and the products of combustion. The very wide dynamic ranges of real-time analyses of BVOCs in air achieved by SIFT-MS and PTR-MS - from sub-ppbv to tens of ppmv - ensure that these analytical methods will be applied to many other media, especially when combined with gas-chromatography methods, as recently trialed.     

Field air analysis with SPME device

Solid-phase microextraction (SPME) devices were used for a wide scope of air-monitoring including field sampling and analysis of volatile organic compounds (VOCs), formaldehyde, and particulate matter (PM) in air. Grab (instantaneous) and time-weighted average (TWA) sampling were accomplished using exposed and retracted SPME fibers, respectively. Sampling time varied from 1 to 75 min, followed by analysis with a gas chromatograph (GC). A portable GC equipped with unique, in-series detectors: photoionization (PID), flame ionization (FID), and dry electrolytic conductivity (DELCD), provided almost real-time analysis and speciation for common VOCs during an indoor air quality surveys. Indoor air samples collected with SPME devices were compared with those collected using conventional National Institute for Occupational Safety and Health (NIOSH) methods. Air concentrations measured with the SPME device were as low as 700 parts-per-trillion (ppt) for semi-volatile organic compounds. SPME methodology proved to be more sensitive than conventional methods, and provided a simple approach for fast, cost-effective sampling and analysis of common VOCs in indoor air. SPME technology combined with fast portable GC reduced the sampling and analysis time to less than 15 min. The configuration offered the conveniences of immediate on-site monitoring and decision making, that are not possible with conventional methods. In addition, SPME fibers were applied to sampling of particulate matter in diesel engine exhaust. Linear uptake and particulate build-up on the fiber were observed. Preliminary research suggests that SPME fibers could also be applied to sampling of airborne particulate matter.     

Sorbent-based sampling methods for volatile and semi-volatile organic compounds in air. Part 2. Sorbent selection and other aspects of optimizing air monitoring methods

Sorbent tubes/traps are widely used in combination with gas chromatographic (GC) analytical methods to monitor the vapour-phase fraction of organic compounds in air. Applications range from atmospheric research and ambient air monitoring (indoor and outdoor) to occupational hygiene (personal exposure assessment) and measuring chemical emission levels. Part 1 of this paper reviewed the main sorbent-based air sampling strategies including active (pumped) tube monitoring, diffusive (passive) sampling onto sorbent tubes/cartridges plus sorbent trapping/focusing of whole air samples that are either collected in containers (such as canisters or bags) or monitored online. Options for subsequent extraction and transfer to GC(MS) analysis were also summarised and the trend to thermal desorption (TD)-based methods and away from solvent extraction was explained. As a result of this trend, demand for TD-compatible sorbents (alternatives to traditional charcoal) is growing. Part 2 of this paper therefore continues with a summary of TD-compatible sorbents, their respective advantages and limitations and considerations for sorbent selection. Other analytical considerations for optimizing sorbent-based air monitoring methods are also discussed together with recent technical developments and sampling accessories which have extended the application range of sorbent trapping technology generally.     

Determination of complex mixtures of volatile organic compounds in ambient air: an overview

This article reviews developments in the sampling and analysis of volatile organic compounds (VOCs) in ambient air since the 1970s, particularly in the field of environmental monitoring. Global monitoring of biogenic and anthropogenic VOC emissions is briefly described. Approaches used for environmental monitoring of VOCs and industrial hygiene VOC exposure assessments are compared. The historical development of the sampling and analytical methods used is discussed, and the relative advantages and disadvantages of sorbent and canister methods are identified. Overall, there is considerable variability in the reliability of VOC estimates and inventories. In general, canister methods provide superior precision and accuracy and are particulary useful for the analysis of complex mixtures of VOCs. Details of canister methods are reviewed in a companion paper. C. C. Austin is an Invited Scientist of the National Research Council of Canada.     

An improved Sampling Strategy for the Measurement of VOCs in Air,Based on Cooled Sampling and Analysis by Thermodesorption-GC-MS/FID

Abstract

Reliable and comprehensive sampling methods are required to obtain accurate data for VOC concentrations in air samples. The major drawback of the adsorption tube sampling method, widely employed in environmental studies, is the fact that C₂ compounds are usually not trapped quantitatively.

The focus of this work was thus to improve sampling based on adsorption tubes packed with Molsieve and Carbosieve. To improve the sampling efficiency for the C₂ compounds, a cooling device, based on Peltier cooling was constructed, which could be operated at a temperature down to ?30°C.

Experiments under laboratory and field conditions were carried out to study the influence of the sampling temperatuie on the recovery of ethane and ethene as the most volatile VOCs. The results clearly demonstrate the need for a cooled sampling device for the analysis of C₂ compounds in air. Under the investigated conditions, the recoveries with ambient temperature sampling were only in the range of 38–46% for ethane and 33–59% for ethene respectively, in comparison to the cooled sampling device. These findings are only valid for the described conditions and can change significantly with temperature and concentration. A generalisation of the recovery is thus very difficult to give.

The use of the sampling device for a field study is reported, where samples were collected simultaneously at three different altitudes in a diurnal profile on the slope of the Schulterberg mountain in Tyrol (Austria).     

An optimized sampling and GC-MS analysis method for benzene in exhaled breath, as a biomarker for occupational exposure

Benzene is known to be toxic and carcinogenic: therefore, in case of exposure to benzene vapours, a reliable biological monitoring procedure is needed, particularly in the field of occupational hygiene. The determination of the concentration of benzene in the exhaled air 8 h after the exposure has been demonstrated to be a significant biomarker, even for low concentrations of airborne benzene vapours. This work presents a sampling and analysis method that optimizes previously described procedures: in the sampling phase, a double-step sample collection in Tedlar bags is used, in order to remove the breath moisture and to standardise the sample volumes. The analytical phase uses a cryogenic trap for the concentration of the air samples to be injected in the GC-MS, without the need for trapping materials, significantly reducing time and costs of the analysis and improving sensitivity. The presented method has been successfully applied to the biological monitoring of a mixed population (occupationally exposed and not exposed subjects, smokers and non-smokers), with a lower detection limit of 1.5 ng of benzene per litre of exhaled air, that is 1/200 of the biological exposure index recommended by the American Conference of Governmental Hygienists.     

Gas chromatography-mass spectrometry determination of 3-mercaptohexan-1-ol and 3-mercaptohexyl acetate in wine: a comparison of headspace solid phase microextraction and solid phase extraction methods

A gas chromatography-mass spectrometry method was established using headspace solid phase microextraction (HS-SPME) as the sampling procedure to analyse 3-mercaptohexan-1-ol (3-MH) and 3-mercaptohexyl acetate (3-MHA), two molecules with a tropical fruit aroma, in wine at trace level. This method offers important advantages, as it neither requires time-consuming sample preparation nor uses dangerous organic compounds, thus making control of wine aroma easier and suitable for routine analysis. As a comparison, a solid phase extraction (SPE) method, already described elsewhere for aroma analysis, was applied to quantify these analytes, extending this exhaustive enrichment to two important thiols. Detection limits for both the approaches were close to the sensory threshold value, resulting lower for the HS-SPME procedure and suitable for requirements in the oenological field. The application of the two proposed methods to 52 wines of different varieties gave similar results.     

Quantification of hydrogen cyanide in humid air by selected ion flow tube mass spectrometry

Following our recent observation that Pseudomonas bacteria in vitro emit hydrogen cyanide, we have found it necessary to investigate the ion chemistry of this compound and to extend the kinetics database for selected ion flow tube mass spectrometry (SIFT-MS) to allow the accurate quantification of HCN in moist air samples, including exhaled breath. Because of the proximity of the proton affinities of HCN and H2O molecules, the presence of water vapour can significantly distort HCN analysis in the presence of water vapour and a more sophisticated analytical procedure has to be developed. Thus, the reactions of H3O+(H2O)0,1,2,3 ions with HCN molecules have been studied in the presence of varying concentrations of water vapour, reactions on which SIFT-MS analysis of HCN relies. The results of these experiments have allowed an analytical procedure to be developed which has extended the kinetics database of SIFT-MS, such that HCN can now be quantified in humid air and in exhaled breath.     

A procedure for sampling and analysis of air for energetics and related compounds

A procedure for the sampling and analysis of energetics and related compounds in the atmosphere is described. The basic procedure consists of the collection of air samples using sampling cartridges containing XAD-2 resin, extraction of the resin with isoamyl acetate, and an analysis of the extract using gas chromatography with electron capture detection. Modifications and additions to this procedure are discussed, such as the use of a prefilter before the resin sampler to collect particulates and the use of a mass selective detector to analyze for some propellant compounds of interest or for quantitative confirmation purposes. Two differing sizes of samplers are evaluated according to the air volumes required for collection. The procedure is tested through the analysis of spiked resin samples, which had air pulled through them for periods of time corresponding with the required sampling volumes. This procedure has application toward the measurement of energetic residues in atmospheres resulting from weapons testing and operations during training exercises involving munitions.     

Determination of inorganic pollutants in atmospheric aerosols

The main sources of air pollution by inorganic metal compounds, the sampling of aerosol particles, and sample preparation for analysis are considered. The nondestructive and destructive methods of analysis are compared, and their advantages and disadvantages are specified. The development of synthetic reference samples, which are used to determine a calibration function and to verify the accuracy of analytical results for both of the methods, is considered.     

Environmental formaldehyde analysis by active diffusive sampling with a bundle of polypropylene porous capillaries followed by capillary zone electrophoretic separation and contactless conductivity detection

Compared to other volatile carbonylic compounds present in outdoor air, formaldehyde (CH(2)O) is the most toxic, deserving more attention in terms of indoor and outdoor air quality legislation and control. The analytical determination of CH(2)O in air still presents challenges due to the low-level concentration (in the sub-ppb range) and its variation with sampling site and time. Of the many available analytical methods for carbonylic compounds, the most widespread one is the time consuming collection in cartridges impregnated with 2,4-dinitrophenylhydrazine followed by the analysis of the formed hydrazones by HPLC. The present work proposes the use of polypropylene hollow porous capillary fibers to achieve efficient CH(2)O collection. The Oxyphan fiber (designed for blood oxygenation) was chosen for this purpose because it presents good mechanical resistance, high density of very fine pores and high ratio of collection area to volume of the acceptor fluid in the tube, all favorable for the development of air sampling apparatus. The collector device consists of a Teflon pipe inside of which a bundle of polypropylene microporous capillary membranes was introduced. While the acceptor passes at a low flow rate through the capillaries, the sampled air circulates around the fibers, impelled by a low flow membrane pump (of the type used for aquariums ventilation). The coupling of this sampling technique with the selective and quantitative determination of CH(2)O, in the form of hydroxymethanesulfonate (HMS) after derivatization with HSO(3)(-), by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D) enabled the development of a complete analytical protocol for the CH(2)O evaluation in air.     

Calibration of complex mixtures in one sweep

The calibration of extremely complex humid gas-phase mixtures – often required in ion mobility spectrometry applications – is challenging, even when high-performance calibration gas generators such as HovaCAL® are applied. Here, we describe an approach to develop and apply mixtures of VOCs in one channel of such a calibration gas generator for a complex calibration in one sweep. As an example, a mixture of so-called “Signs of Life” – compounds available in the exhaled breath and/or in the sweat of everybody was used. The procedure of developing the appropriate mixture and the results of a successful calibration of a GC-ion mobility spectrometer are presented.     

Potential of solid-phase microextraction fibers for the analysis of volatile organic compounds in air.

This work presents the usefulness of five different solid-phase microextraction fibers in the screening of volatile organic compound (VOC) traces in air samples. The performances of these fibers are compared by studying the sorption kinetics in an equimolar gaseous mixture of eleven VOCs. For each fiber, static and dynamic sampling are compared. It is shown that repeatability is better for the dynamic mode (less than 6% for dynamic sampling and 10% for static sampling). The equilibrium time and the sensitivity vary considerably from one fiber type to another. As an example, the classical polydimethylsiloxane (PDMS) coating presented the shortest equilibration time (5 min) but also the poorest sensitivity, whereas the PDMS-Carboxen showed the longest extraction time but the greatest sensitivity. The estimation of the quantity of VOCs fixed on the target fiber allows for the determination of the different affinities of the compounds with the involved sorbent and relates them with physicochemical properties of the molecules. Competitive sorption is observed for the fibers involved with the adsorption process (i.e., PDMS-divinylbenzene and PDMS-Carboxen fibers). These competitions can lead to SPME calibration problems and thus bad quantitative analysis.     

Development of SPME on-fiber derivatization for the sampling of formaldehyde and other carbonyl compounds in indoor air

Solid-phase microextraction on-fiber derivatization applied to carbonyl compounds is known, but application to indoor air is poorly developed and the methods deserve to be complemented and optimized. In this work, two derivatization reagents, pentafluorophenylhydrazine and o-2,3,4,5,6-(pentaflurobenzyl)hydroxylamine (PFBHA), and three fiber coatings were tested in order to select the best combination. As Carboxen-based coatings were proven to induce the formation of by-products during the thermal desorption step, a polydimethylsiloxane–divinylbenzene fiber in association with PFBHA was finally chosen. The study of the derivatization kinetics showed that the reaction of PFBHA with carbonyl compounds was instantaneous, except for acetone. Analyses were performed by gas chromatography coupled with flame ionization detection and mass spectrometry. For 5 min fiber exposure, the limits of detection are below 0.5 μg m^-3 in selected ion monitoring mode, the reproducibility was 15 % on average, and the linearity of the calibration curves was satisfactory. For on-site application, the influence of air humidity and the conditions in which the impregnated fibers were stored were studied. It is possible to store the fibers for 3 days before and for at least 2 days after sampling. The relative humidity of air was shown to have no influence on solid-phase microextraction sampling in the range from 0 to 70 %. For formaldehyde, the method was compared with sampling on 2,4-dinitrophenylhydrazine cartridges, and the first results showed good agreement. Finally, the method was applied to three different indoor environments to check its feasibility.     

One-year time series of investigations of analytes within human breath using ion mobility spectrometry

Ion mobility Spectrometry is used to detect volatile analytes within human breath directly. Many volatile organic compounds (VOC) show significant day-to-day variation in the signal height related to the concentration of the analyte, although the breath collection had been performed under the same conditions with respect to similar sampling procedure, similar dead volume, similar measurement time, and measurement conditions. Variations of 8 different analytes are investigated over a time period of 11 months in the exhaled breath of the same person in the same room environment. The individual variability is reported for Benzothiazole; D-Limonene; Eucalyptol; Decamethylcyclopentasiloxane; Decanal; 1-Hexanol, 2-ethyl-; Cyclohexanone, 5-methyl-2-(1-methylethyl) and Nonanal. The paper shows, that the individual variability must be taken into consideration to relate the findings to medical questions. Therefore, the room air concentration of VOCs must be taken into account, so that the difference between exhaled and inhaled air has to be used as indicator. Finally, starting with individual variabilities, the normal variation related to the specific analyte should be considered in addition.     

Passive sampling application to control air quality in interior of new vehicles

The investigation of air pollution is a highly important field of research. Air quality in a vehicle’s interior has attracted growing attention since people spend much of their time in vehicles and those frequently travelling in new cars are exposed to harmful compounds. The main air pollutants inside new vehicles are volatile organic compounds (VOCs), present as a result of interior materials’ de-gassing. Among the sampling methods used in indoor air quality research, active sampling for VOCs collection is one method that has been extensively described and applied. The present study sought to implement passive sampling with Radiello® samplers to collect air samples directly in the car factory. The results from passive sampling were compared with results derived from active sampling using Carbograph 1TD and silicagel coated with 2,4-dinitrophenylhydrazine cartridges, based on previously validated methods. The identification and quantification of organic compounds was performed using gas chromatography with flame ionisation coupled with a mass spectrometer after thermal desorption. Aldehydes were determined by means of high-performance liquid chromatography. In the present study, the results obtained with the use of active and passive methods of air sampling were compared, correlations between the two sampling methods were designated and the repeatability of passive sampling was detailed.     

A multi-residue method for characterization and determination of atmospheric pesticides measured at two French urban and rural sampling sites

The extensive use of pesticides to protect agricultural crops can result in the transfer of these compounds into the atmosphere and their diffusion towards urban areas. Precise evaluation of the geographic impact of this type of pollution is important environmentally. In this paper, analytical methods for the sampling, characterization, and determination of agricultural pesticides in air were developed; the methods were then applied in the Paris and Champagne regions. Sixteen pesticides belonging to nine chemical families were monitored. Sampling was carried out in urban (Paris) and rural (Aube district) sites, utilizing either a high-volume pump (12.5 m³ h^–1) (urban site) or a low-volume pump (2.3 m³ h^–1) for the rural site. Quartz filters and polyurethane foams (PUF) were used for sampling in all cases. After extracting the samples and concentrating the recovered solutions, high-performance liquid chromatography (HPLC) analysis with UV detection was performed. Identification of the pesticides was confirmed by applying to the HPLC measurements a novel UV-detection procedure based on the normalized absorbance variation with wavelength (Noravawa procedure). The presence of metsulfuron methyl, isoproturon, linuron, deltamethrin (and/or malathion), and chlorophenoxy acids (2,4-D and MCPP) was found at the urban sampling site at levels ranging from about 1 to 1130 ng m^–3 of air, depending on the compound and sampling period. On the rural sampling site residues of isoproturon, deltamethrin (and/or malathion), MCPP, and 2,4-D were generally detected at higher levels (19–5130 ng m^–3) than on the urban site, as expected. The effects of the weather conditions and agricultural activity on the atmospheric concentrations of pesticides are discussed, as are long-range atmospheric transfer processes for these pesticides.     

Eavaluation of automatic thermal desorption–capillary GC for determination of semivolatile organic compounds (SVOCS) in indoor air

Some data on a newly developed filter/sorbent indoor air SVOC sampling device for thermal desorption analyiss are described. Thermal desorption of SVOCs spiked on Tenax had reponse factors identical to on-column injection except for highly polar compounds like fatty acids. SVOCs spiked on quartz fiber filters had response factors that on an average were 80% of the on-column response factors (66% for oxygen containing compounds and 87% for non-oxygen compounds) Low nanogram on-tube amounts of SVOCs were found generally to have lower recoveries than larger amounts from both Tenax and quart fiber filters. This appeared to be explained in part by a relatively larger “memory” effect and lower desorption efficiency. In addition, it was indicated that the “memory” effect was an important source of background contaminations that might impair analysis of low nanogram on-tube amounts of some SVOCs. Polar SVOCs. Polar SVOCs in the gas phase appear to adsorbto the quartz fiber filters. This functions as a precleaning of the sample and thus minimizes the problem with coeluting peaks. The relative standard from nine duplicate samples appeared to be sufficiently low to distinguish a day variation.