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.     

Flow-through system for the generation of standard aqueous solution of polycyclic aromatic hydrocarbons

Standard aqueous solution of organic pollutants is used for the development of analysis methods and novel water sampling devices. The use of solid-phase microextraction (SPME) and other novel technologies for research in water sampling and analysis requires systems for the reliable generation of standard aqueous solution. In this communication, a new flow-through system based on permeation is introduced for the generation of standard aqueous solution of polycyclic aromatic hydrocarbons (PAHs). The main difference between the new developed system and typical system is that the syringe pump was changed with a permeation generator. The generator-based permeation offers many advantages, including convenient, inexpensive, solvent-free, long lifetime and production of high concentrations of the target analytes. The observed change in the concentration of the six PAH compounds was less than 20% over 3 months.     

Air sampling of aromatic hydrocarbons in the presence of ozone by solid-phase microextraction

Effects of ozone on air sampling of standard gas mixtures of aromatic hydrocarbons were tested using solid-phase microextraction (SPME). Standard concentrations of ozone ranging from 10 ppb (v/v) to 6400 ppm (v/v) were generated using an in-house built ozone generator based on corona discharge. Effects of temperature, discharge voltage, and oxygen flow on the ozone generation were tested. The working dc voltage had the greatest effect on generated ozone concentration and was proportional to the ozone concentration. Generation temperature and oxygen flow rate were inversely proportional to ozone concentrations. Produced ozone was mixed with standard benzene, toluene, ethylbenzene, and xylenes (BTEX) gas at less than 100 ppb (v/v). Air samples were collected with poly(dimethylsiloxane) (PDMS) 100 microm SPME fibers and analyzed by gas chromatography (GC)-flame ionization detection (FID) and GC-MS. Significant reductions of BTEX concentrations were observed. In addition, some products of BTEX-ozone-oxygen reactions were identified. SPME worked well as a rapid sampler for BTEX and BTEX-ozone-oxygen reaction products. No significant deterioration of the PDMS coating and no significant reduction of absorption capacity were observed after repeated exposure to ozone.     

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.     

Solid-phase microextraction as a novel air sampling technology for improved, GC-olfactometry-based assessment of livestock odors

Air sampling and characterization of odorous livestock gases is one of the most challenging analytical tasks. This is because of low concentrations, physicochemical properties, and problems with sample recoveries for typical odorants. Livestock operations emit a very complex mixture of volatile organic compounds (VOCs) and other gases. Many of these gases are odorous. Relatively little is known about the link between characteristic VOCs/gases and, specifically, about the impact of characteristic odorants downwind from sources. In this research, solid-phase microextraction (SPME) is used for field air sampling of odors downwind from swine and beef cattle operations. Sampling time ranges from 20 min to 1 h. Samples are analyzed using a commercial gas chromatography-mass spectrometry-olfactometry system. Odor profiling efforts are directed at odorant prioritization, with respect to distance from the source. The results indicate the odor downwind is increasingly defined by a smaller number of high-priority odorants. These "character defining" odorants appear to be dominated by compounds of relatively low volatility, high molecular weight, and high polarity. In particular, p-cresol alone appears to carry much of the overall odor impact for swine and beef cattle operations. Of particular interest is the character-defining odor impact of p-cresol as far as 16 km downwind of the nearest beef cattle feedlot. The findings are highly relevant to scientists and engineers working on improved air sampling and analysis protocols and on improved technologies for odor abatement. More research evaluating the use of p-cresol and a few other key odorants as a surrogate for overall odor dispersion modeling is warranted.     

Sampling and analysis of volatile organic compounds in bovine breath by solid-phase microextraction and gas chromatography-mass spectrometry

A relatively noninvasive method consisting of a face mask sampling device, solid-phase microextraction (SPME) fibers, and a gas chromatography-mass spectrometry (GC-MS) for the identification of volatile organic compounds (VOCs) in bovine breath was developed. Breath of three morbid steers with respiratory tract infections and three healthy steers were sampled seven times in 19 days for 15 min at each sampling. The breath VOCs adsorbed on the divinylbenzene (DVB)-Carboxen-polydimethyl siloxane (PDMS) 50/30 microm SPME fibers were transported to a laboratory GC-MS system for separation and identification with an in-house spectral library of standard chemicals. A total of 21 VOCs were detected, many of them for the first time in cattle breath. Statistical analyses using Chi-square test on the frequency of detection of each VOC in each group was performed. The presence of acetaldehyde (P < or = 0.05) and decanal (P < or = 0.10) were associated more with clinically morbid steers while methyl acetate, heptane, octanal, 2,3-butadione, hexanoic acid, and phenol were associated with healthy steers at P < or = 0.10. The results suggest that noninvasive heath screening using breath analyses could become a useful diagnostic tool for animals and humans.     

Sorbent-based sampling methods for volatile and semi-volatile organic compounds in air: Part 1: Sorbent-based air monitoring options

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. Target compounds range in volatility from acetylene and freons to phthalates and PCBs and include apolar, polar and reactive species. Airborne vapour concentrations will vary depending on the nature of the location, nearby pollution sources, weather conditions, etc. Levels can range from low percent concentrations in stack and vent emissions to low part per trillion (ppt) levels in ultra-clean outdoor locations. Hundreds, even thousands of different compounds may be present in any given atmosphere. GC is commonly used in combination with mass spectrometry (MS) detection especially for environmental monitoring or for screening uncharacterised workplace atmospheres. Given the complexity and variability of organic vapours in air, no one sampling approach suits every monitoring scenario. A variety of different sampling strategies and sorbent media have been developed to address specific applications. Key sorbent-based examples include: active (pumped) sampling onto tubes packed with one or more sorbents held at ambient temperature; diffusive (passive) sampling onto sorbent tubes/cartridges; on-line sampling of air/gas streams into cooled sorbent traps; and transfer of air samples from containers (canisters, Tedlar^® bags, etc.) into cooled sorbent focusing traps. Whichever sampling approach is selected, subsequent analysis almost always involves either solvent extraction or thermal desorption (TD) prior to GC(/MS) analysis. The overall performance of the air monitoring method will depend heavily on appropriate selection of key sampling and analytical parameters. This comprehensive review of air monitoring using sorbent tubes/traps is divided into 2 parts. (1) Sorbent-based air sampling option. (2) Sorbent selection and other aspects of optimizing sorbent-based air monitoring methods. The paper presents current state-of-the-art and recent developments in relevant areas such as sorbent research, sampler design, enhanced approaches to analytical quality assurance and on-tube derivatisation.     

Application of solid-phase microextraction for determination of organic vapours in gaseous matrices

This paper reviews the practical applications of solid-phase microextraction (SPME) in the analysis of organic vapours which are pollutants of atmospheric air, indoor air and workplace air. Applications to headspace of solids and liquids such as different waters, soils, food, etc., are also included. Problems related to calibration in SPME analysis of gaseous matrices are also dealt with. Calibration procedures and apparatus for generation of standard gaseous mixtures are described. Advantages and limitations of SPME based gas chromatographic methods of air organic pollutants are discussed.     

Simultaneous sampling and analysis of indoor air infested with Cimex lectularius L. (Hemiptera: Cimicidae) by solid phase microextraction,thin film microextraction and needle trap device

Air in a room infested by Cimex lectularius L. (Hemiptera: Cimicidae) was sampled simultaneously by three different sampling devices including solid phase microextraction (SPME) fiber coatings, thin film microextraction (TFME) devices, and needle trap devices (NTDs) and then analyzed by gas chromatography–mass spectrometry (GC–MS). The main focus of this study was to fully characterize indoor air by identifying compounds extracted by three different microextraction formats and, therefore, perform both the device comparison and more complete characterization of C. lectularius pheromone. The NTD technique was capable of extracting both (E)-2-hexenal and (E)-2-octenal, which were previously identified as alarm pheromones of bedbugs, and superior NTD recoveries for these two components allowed reliable identification based on mass spectral library searching and linear temperature programmed retention index (LTPRI) technique. While the use of DVB/CAR/PDMS SPME fiber coatings provided complementary sample fingerprinting and profiling results, TFME sampling devices provided discriminative extraction coverage toward highly volatile analytes. In addition to two alarm pheromones, relative abundances of all other analytes were recorded for all three devices and aligned across all examined samples, namely, highly infested area, less infested area, and control samples which were characterized by different bedbug populations. The results presented in the current study illustrate comprehensive characterization of infested indoor air samples through the use of three different non-invasive SPME formats and identification of novel components comprising C. lectularius pheromone, therefore, promising future alternatives for use of potential synthetic pheromones for detection of infestations.     

Optimization of a novel headspace–solid‐phase microextraction–gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devices

Medical devices sterilized by ethylene oxide (EtO) retain trace quantities of EtO residuals, which may irritate patients' tissue. Reliably quantifying trace level EtO residuals in small medical devices requires an extremely sensitive analytical method. In this research, a Doehlert uniform shell design was utilized in obtaining a response surface to optimize a novel headspace–solid‐phase microextraction–gas chromatographic (HS‐SPME‐GC) method developed for analyzing trace levels of EtO residuals in sterilized medical devices, by evaluating sterilized, polymer‐coated, drug‐eluting cardiovascular stents. The effects of four independent experimental variables (HS‐SPME desorption time, extraction temperature, GC inlet temperature and extraction time) on GC peak area response of EtO were investigated simultaneously and the most influential experimental variables determined were extraction temperature and GC inlet temperature, with the fitted model showing no evidence of lack‐of‐fit. The optimized HS‐SPME‐GC method demonstrated overall good linearity/linear range, accuracy, repeatability, reproducibility, absolute recovery and high sensitivity. This novel method was successfully applied to analysis of trace levels of EtO residuals in sterilized/aerated cardiovascular stents of various lengths and internal diameter, where, upon heating, trace EtO residuals fully volatilized into HS for extraction, thereby nullifying matrix effects. As an alternative, this novel HS‐SPME‐GC method can offer higher sensitivity compared with conventional headspace analyzer‐based sampling. Copyright © 2009 John Wiley & Sons, Ltd.     

A portable automated system for trace gas sampling in the field and stable isotope analysis in the laboratory

A computer-controllable mobile system is presented which enables the automatic collection of 33 air samples in the field and the subsequent analysis for delta13C and delta18O stable isotope ratios of a carbon-containing trace gas in the laboratory, e.g. CO2, CO or CH4. The system includes a manifold gas source input for profile sampling and an infrared gas analyzer for in situ CO2 concentration measurements. Measurements of delta13C and delta18O of all 33 samples can run unattended and take less than six hours for CO2. Laboratory tests with three gases (compressed air with different pCO2 and stable isotope compositions) showed a measurement precision of 0.03 per thousand for delta13C and 0.02 per thousand for delta18O of CO2 (standard error (SE), n = 11). A field test of our system, in which 66 air samples were collected within a 24-hour period above grassland, showed a correlation of 0.99 (r2) between the inverse of pCO2 and delta13C of CO2. Storage of samples until analysis is possible for about 1 week; this can be an important factor for sampling in remote areas. A wider range of applications in the field is open with our system, since sampling and analysis of CO and CH4 for stable isotope composition is also possible. Samples of compressed air had a measurement precision (SE, n = 33) of 0.03 per thousand for delta13C and of 0.04 per thousand for delta18O on CO and of 0.07 per thousand for delta13C on CH4. Our system should therefore further facilitate research of trace gases in the context of the carbon cycle in the field, and opens many other possible applications with carbon- and possibly non-carbon-containing trace gases.     

SPME sampling of BTEX before GC/MS analysis: examples of outdoor and indoor air quality measurements in public and private sites

This article presents the results of an exploratory application of the Solid Phase MicroExtraction (SPME) technique to the analysis of BTEX (benzene, toluene, ethylbenzene and xylenes) at the microg/m3 level in outdoor and indoor air. The salient features of the method validation are reported. As shown by the various examples of field sampling described, SPME technique appears as a method of choice for fast qualitative analysis and quantitative determination of Volatile Organic Compounds (VOC). The small dimensions of the SPME sampling system and the short sampling time let envisage its utilisation for the rapid diagnostic of outdoor and indoor air quality.     

Determination of benzene, toluene, ethylbenzene and xylenes in air by solid phase micro-extraction/gas chromatography/mass spectrometry

The aim of the study was to analyse BTEX compounds (benzene, toluene, ethylbenzene, xylenes) in air by solid phase micro-extraction/gas chromatography/mass spectrometry (SPME/GC/MS), and this article presents the features of the calibration method proposed. Examples of real-world air analysis are given. Standard gaseous mixtures of BTEX in air were generated by dynamic dilution. SPME sampling was carried out under non-equilibrium conditions using a Carboxen/PDMS fibre exposed for 30 min to standard gas mixtures or to ambient air. The behaviour of the analytical response was studied from 0 to 65 g/m³ by adding increasing amounts of BTEX to the air matrix. Detection limits range from 0.05 to 0.1 g/m³ for benzene, depending on the fibre. Inter-fibre relative standard deviations (reproducibility) are larger than 18%, although the repeatability for an individual fibre is better than 10%. Therefore, each fibre should be considered to be a particular sampling device, and characterised individually depending on the required accuracy. Sampling indoor and outdoor air by SPME appears to be a suitable short-delay diagnostic method for volatile organic compounds, taking advantage of short sampling time and simplicity.     

Graphene based chemiresistor sensors for the detection of toxic air pollutants: A theoretical overview

The advancements in present world like industrial revolution, transport system, agriculture, food industry, pharmaceutical industry and electricity generation have made our life easy and comfortable in many aspects but they also have deleterious effects on our life. The pollution from industries, household waste, combustion of fossils etc. has introduced many harmful chemicals in air and water which have badly affected the life on our planet. The presence of undesirable gases in air has serious adverse effects on health and quality of life. Therefore, monitoring of these substances becomes important.Graphene based chemiresistor sensor are proved to be promising materials for the detection of toxic air pollutants. This article summarizes the recent progress of Density functional theory (DFT) based studies in the field of graphene based gas sensors. This article discusses the working mechanism of graphene based chemiresistor and also provides the information that how the sensing ability can be enhanced. The information given in the article will help the young researchers in the selection of suitable dopant and nano-clusters for graphene based surfaces to make them more selective and sensitive towards the analytes.     

Passive sampling of airborne furan indoors by solid-phase microextraction

Furan may be formed in food under heat treatment and is highly suspected to appear in indoor air. The possible exposure to indoor furan raises concerns because it has been found to cause carcinogenicity and cytotoxicity in animals. To determine airborne furan, solid-phase microextraction (SPME) technique was utilised as a diffusive sampler. The Carboxen/Polydimethylsiloxane (CAR/PDMS, 75 μm) fibre was used, and the SPME fibre assembly was inserted into a polytetrafluoroethene tubing. Furan of known concentrations was generated in Tedlar gas bags for the evaluation of SPME diffusive samplers. After sampling, the sampler was inserted into the injection port of a gas chromatograph coupled with a mass spectrometer (GC/MS) for thermal desorption and analysis. Validation of the SPME device with active sampling by charcoal tube was performed side by side as well. The charcoal tube was desorbed by acetone before analysis with GC/MS. The experimental sampling constant of the sampler was found equal to (9.93 ± 1.28) × 10^?3 (cm³ min^?1) at 25°C. Furthermore, side-by-side validations between SPME device and charcoal tube showed linear relationship with r = 0.9927. The designed passive sampling device for furan has the advantages of both passive sampling and SPME technique and looks suitable for assessing indoor air quality.     

Characterization of volatile organic compounds and odorants associated with swine barn particulate matter using solid-phase microextraction and gas chromatography-mass spectrometry-olfactometry

Swine operations can affect air quality by emissions of odor, volatile organic compounds (VOCs) and other gases, and particulate matter (PM). Particulate matter has been proposed to be an important pathway for carrying odor. However, little is known about the odor-VOCs-PM interactions. In this research, continuous PM sampling was conducted simultaneously with three collocated TEOM 1400a analyzers inside a 1000-head swine finish barn located in central Iowa. Each TEOM was fitted with total suspended particulate (TSP), PM-10, PM-2.5 and PM-1 preseparators. Used filters were stored in 40 mL vials and transported to the laboratory. VOCs adsorbed/absorbed to dust were allowed to equilibrate with vial headspace. Solid-phase microextraction (SPME) Carboxen/polydimethylsiloxane (PDMS) 85 microm fibers were used to extract VOCs. Simultaneous chemical and olfactometry analyses of VOCs and odor associated with swine PM were completed using a gas chromatography-mass spectrometry-olfactometry (GC-MS-O) system. Fifty VOCs categorized into nine chemical function groups were identified and confirmed with standards. Five of them are classified as hazardous air pollutants. VOCs were characterized with a wide range of molecular weight, boiling points, vapor pressures, water solubilities, odor detection thresholds, and atmospheric reactivities. All characteristic swine VOCs and odorants were present in PM and their abundance was proportional to PM size. However, the majority of VOCs and characteristic swine odorants were preferentially bound to smaller-size PM. The findings indicate that a significant fraction of swine odor can be carried by PM. Research of the effects of PM control on swine odor mitigation is warranted.     

Use of solid-phase microextraction for the detection of acetic acid by ion-trap gas chromatography-mass spectrometry and application to indoor levels in museums

A simple and efficient method using solid-phase microextraction (SPME) and gas chromatography-ion trap mass spectrometry (GC-ITMS) was developed for the analysis of acetic acid in air. The choice of the SPME fibre revealed to be critical as well as the sampling and desorption time. A dilution vessel was used for calibration. The precision of the method was found to be 4.7% relative standard deviation (RSD) and the detection limit 5.7 microg m(-3). The SPME-GC-MS technique was applied to the analysis of acetic acid in museum atmospheres.     

Analysis of Wine Bouquet Components Using Headspace Solid-Phase Microextraction-Capillary Gas Chromatography

Headspace solid-phase microextraction (HS/SPME) was studied and optimized for the capillary gas chromatographic (CGC) analysis of wine aroma compounds. The results were compared with those obtained using the direct sampling mode (DI/SPME) and using liquid/liquid extraction with Kaltron. The aromatic patterns obtained by HS/SPME-CGC were applied to the chemometric classification of wine varieties. The HS/SPME-CGC standard additional method is an appropriate technique for the quantitative analysis of volatile wine aroma compounds.     

An isotopic dilution approach for 1,3-butadiene tailpipe emissions and ambient air monitoring

An isotopic dilution approach for 1,3-butadiene analysis in gaseous samples is presented. The methodology is based on active sampling on sorbent tubes and subsequent analysis by thermal desorption into a gas chromatography/mass spectrometry system. By adding a perdeuterated internal standard onto the sorbent tubes before sampling, and using mass spectrometric detection, the methodology gives high accuracy for this unstable analyte. The method has been used to monitor 1,3-butadiene ambient air concentrations in a residential area in proximity to a heavy-traffic roadway over a one-week period, for comparison with other traffic-related pollutants analysed by standard procedures. It has also been used to determine tailpipe emissions of two vehicles by standard emission testing procedures in a dynamometer. These vehicles were chosen as examples of low- and high-end emission rate vehicles, i.e., an old no-catalytic converter Otto engine and a new direct-injection diesel engine with catalytic converter. Exhaust gas emissions were 0.052 and 35.85 mg/km, reflecting differences in fuel, engine design, age, and presence (or not) of a catalytic abatement system. The ambient air results showed a weekly average concentration of 1,3-butadiene of 0.53 microg/m(3).     

A Comparison of SnifProbe and SPME for Aroma Sampling

The popular solid phase micro extraction (SPME) device and method is compared with SnifProbe (Gordin and Amirav in J Chromatogr A 903:155–172, 2000) in their application for coffee aroma sampling for its analysis. The main difference between SPME and SnifProbe is in the relative motion of the sampled air. While SPME is based on static air sampling and the achievement of equilibrium, SnifProbe is based on active air pumping through the adsorption trap. A second important difference concerns the sample introduction into the GC injector for its intra injector thermal desorption. SPME is based on the use of a special syringe for sample introduction without any change to the injector, while SnifProbe requires a ChromatoProbe for sample introduction. We found that as a result of these differences, while SnifProbe provides a more faithful (representative) headspace and aroma sample collection, SPME is characterized by major compound dependent sample bias. In addition, SnifProbe enabled much faster sample collection than SPME. Since SnifProbe uses the ChromatoProbe for sample introduction into the GC, bigger sample collection/trapping devices such as silicone tubing can be used, and as a result, over ten times superior SnifProbe sensitivity (versus SPME) was demonstrated. Additional SnifProbe and SPME features are compared and discussed.