Evaluation of a passive sampler for airborne formaldehyde

Summary A diffusive sampler for the large scale routine determination of airborne formaldehyde was developed. Formaldehyde is sampled in a badge-type passive sampler containing a 2,4-dinitrophenylhydrazine-coated filter paper as sampling layer. Formaldehyde is immediately converted to the corresponding hydrazone, which, after desorption with acetonitrile, is separated and quantified by gradient HPLC using UV detection at 345 nm. Calibration was done via an active sampling method and showed an excellent, time- and concentration-independent linear performance of the diffusive samplers. A detection limit of about 0.05 ml/m³·h (ppm·h) and a relative standard deviation of about 10% ensured a good analytical reliability. By testing the influence of air movements at the sampler surface, a minimum air velocity of 10 cm/s was found necessary to ensure representative sampling.     

Workplace monitoring of isocyanates using ion trap liquid chromatography/tandem mass spectrometry

A sensitive liquid chromatography/ion trap tandem mass spectrometry method was developed for the qualitative and quantitative detection of isocyanates in air. The method is based on derivatization of isocyanates with 1-(2-methoxyphenyl)piperazine during air sampling. The extracts are analyzed using an ion trap LC/MS system equipped with an electrospray (ESI) ion source. The method shows high linearity, specificity, accuracy and precision. The limits of detection are 40x to 55x lower than with UV-based methods.     

Application of tryptamine as a derivatising agent for airborne isocyanate determination. Part 3. Evaluation of total isocyanates analysis by high-performance liquid chromatography with fluorescence and amperometric detection

Determination of total airborne isocyanates using tryptamine as the derivatising agent was investigated. Tryptamine derivatised isocyanates were analysed by reversed-phase high-performance liquid chromatography (HPLC). The column was equipped with dual detectors of fluorescence emission and amperometric oxidation. The characteristics of fluorescence emission and amperometric oxidation of tryptamine were retained even after its reaction with isocyanates. With this unique behaviour, all tryptamine derivatised isocyanates can be quantified using HPLC by employing a single, pure derivative, such as tryptamine derivatised hexamethylene diisocyanate as the calibration standard. This is especially important for analysing polymeric isocyanates when identical calibration standards are not always available. The applicability of this method for air sampling was evaluated by comparison with the established method of Bagon et al. involving 1-(2-methoxyphenyl)piperazine. Simulation of air sampling was performed in a Test Atmosphere Generation System by the vaporisation of toluene diisocyanate. Satisfactory results were obtained, indicating the applicability of this technique for the determination of total airborne isocyanates.     

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.     

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.     

Development of a personal isocyanate sampler based on DBA derivatization on solid-phase microextraction fibers

The design and evaluation of a portable diffusive sampler for isocyanates is described. The sampler employs dibutylamine (DBA) loaded onto 60-microm polydimethylsiloxane-divinylbenzene (PDMS-DVB) solid-phase microextraction (SPME) fibers. The DBA-isocyanate derivative is then desorbed by sonication and analyzed by LC-MS using atmospheric pressure chemical ionization (APCI). The samplers are calibrated (i.e. the uptake rate is calculated) by exposing them to a known concentration of hexamethylene diisocyanate (HDI) in a standard gas-generation chamber. The uptake rate for the proposed method, at room temperature (25 degrees C), is 1.13 pg (min ppb(v))(-1) and the method detection limit is 3.2 microg m(-3), equivalent to less than 10% of the airborne time-weighted average (TWA) exposure limits recommended by both the National Institute for Occupational Safety and Health (NIOSH) and the American Conference of Governmental Industrial Hygienists (ACGIH). Practical points that should be considered when using the SPME device as a diffusive sampler are discussed.     

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.     

Comparison of passive and active sampling methods for the determination of nitrogen dioxide in urban air

Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NO_x-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent. For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the concentration range 15–30 μg NO₂/m³. The detection limit for the passive sampler is 1 μg NO₂/m³ (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NO_x-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO₂/m³, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the breakthrough is below 1%. Received: 3 December 1996 / Revised: 11 March 1997 / Accepted: 15 March 1997     

Measurement techniques for mercury species in ambient air

This review critically evaluates the measurement methodologies most commonly employed for the analysis of the various forms of mercury (Hg) in air. Emphasis is given to the three most common forms of mercury in air [i.e. gaseous elemental mercury (GEM, Hg⁰), reactive gaseous mercury (RGM), and particle-bound mercury (Hg_p)]. Moreover, we also briefly describe methods dealing with gas-phase analysis of organic mercury species (e.g., mostly methyl mercury), as they are also reported to be present in air on rare occasions. To begin with, we describe the approaches to sampling airborne mercury species and associated sample-treatment strategies. We evaluate both conventional and emerging alternative detection techniques for different mercury forms with respect to their applicability in airborne mercury analysis. We also discuss the artifacts and the biases associated with analysis of different mercury species. Finally, the review summarizes current methodological developments for the determination of mercury in air and highlights future prospects for improvements.     

程序升温汽化大体积进样气相色谱法同时测定空气中的甲醛及其他10种羰基污染物（英文）

Long-term indoor-air limit for formaldehyde stipulated by the European Commission is 1 μg/m3,while the World Health Organization has set a threshold of 100 μg/m3 that should not be exceeded for more than 30 min. To date,however,only a few analytical techniques have been developed that can be used to detect formaldehyde at these very restrictive limits. Thus,there is a need to develop for comprehensive methods for analyzing airborne formaldehyde and other carbonyl pollutants in the ambient environment. The aim of this study is to develop a highly sensitive online automated preconcentration gas chromatographic method using large-volume injection with a programmed temperature vaporization injector for the analysis of airborne formaldehyde and ten other carbonyl compounds. The influence of several parameters,such as the maximum volume injected,programmed temperature vaporization transfer time and temperature,carrier gas flow rate,and type of packing material was investigated. After optimization,highly satisfactory results in terms of the absolute and methodological detection limits were achieved,i. e. as low as the μg/m3 level for all the carbonyl pollutants studied. A commercially available sampler,originally designed for active sampling,was evaluated as a passive sampling device;this optimized technique was applied to monitor the concentrations of carbonyl pollutants in the indoor air of ten public buildings in Florence. The strength of this methodology lies both in the low detection limits reached in the simultaneous analysis of a wide group of 2,4-dinitrophenylhydrazine derivatives,and the potential adaptability of this method to other gas chromatographic applications to achieve lower sensitivity.     

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.     

Determination of isocyanates in air

Procedures for the determination of isocyanates in air are considered, including procedures for air sampling with the subsequent analysis and on-line monitoring procedures. Only chemisorption is used for the sampling and preconcentration of isocyanates because of their high reactivity. The data on the reagents in use, the types of sampling devices, and operation conditions are surveyed. Presently, high-performance liquid chromatography is primarily used for the subsequent instrumental analysis of samples. Photometric techniques were used in early studies; more recently, thin-layer chromatography and gas chromatography were introduced. Examples of analysis using other techniques are very few. Methods of on-line monitoring of air (both instrumental techniques and rapidly developed biomonitoring, which is performed simultaneously with the analysis of polluted air) are briefly considered.     

A diffusive sampling device for simultaneous determination of ozone and carbonyls

A new diffusive sampling method for the simultaneous determination of ozone and carbonyls in air has been developed. In this method, silica gel impregnated with a mixture of trans-1,2-bis(2-pyridyl)ethylene (2BPE) and 2,4-dinitrophenylhydrazine (DNPH) is used as the absorbent; further, a porous sintered polyethylene tube (PSP-diffusion filter), which acts as a diffusive membrane, and a small polypropylene syringe (PP-reservoir) for elution of the analytes from the absorbent are used. The carbonyls present in air react with DNPH in the absorbent to form hydrazone derivatives. Concurrently, ozone in the air reacts with 2BPE to form pyridine-2-aldehyde, which immediately reacts with DNPH to form a pyridine-2-aldehyde hydrazone derivative. All the hydrazones derived from airborne carbonyls, including pyridine-2-aldehyde (formed from ozone), are completely separated and analyzed by high-performance liquid chromatography. The sampling rates of ozone (44.6 mL min(-1)) and formaldehyde (72.0 mL min(-1)) are determined by comparison with the rates obtained in an active sampling method. The sampling rates of other carbonyl compounds are calculated from the respective molecular weights according to a rule based on Graham's law. The calculated sampling rates agree with the experimental values. The DSD-BPE/DNPH method is advantageous because it is simple and allows for the simultaneous analysis of ozone and carbonyls.     

MMNTP-a new tailor-made modular derivatization agent for the selective determination of isocyanates and diisocyanates

The synthesis of a new tailor-made derivatization agent for the selective determination of (di)isocyanates is presented. Starting from cyanuric chloride, the reagent 4-methoxy-6-(4-methoxy-1-naphthyl)-1,3,5-triazine-2-(1-piperazine)(MMNTP) is synthesized by subsequent substitution of the three chlorine atoms. This new derivatization agent and the five urea derivatives of phenylisocyanate (PI), hexamethylene-diisocyanate (HDI), toluene-2,4-diisocyanate (2,4-TDI), toluene-2,6-diisocyanate (2,6-TDI) and methylenebisphenyl-4,4-diisocyanate (MDI) show good spectroscopic properties with small compound-to-compound variabilities (RSD([epsilon])= 5.3 %, RSD(relative fluorescence)= 9.4 %). Therefore, using UV detection, a single calibration is needed for the quantification of all diisocyanates and isocyanates respectively. For separation and analysis a HPLC method with a RP column and a binary gradient is presented. All derivatives are separated and show low limits of detection. In addition to the good spectroscopic properties and low limits of detection, good reactivity for the derivatizations at room temperature is observed. The aromatic diisocyanates can be measured immediately whereas aliphatic diisocyanates need 2 h incubation. These advantages make MMNTP a powerful and versatile derivatization agent for (di)isocyanates which is demonstrated by a real sample with solid phase sampling, where the reagent is coated on a sorbent.     

Comparative study of the adsorption performance of an active multi-sorbent bed tube (Carbotrap, Carbopack X, Carboxen 569) and a Radiello(®) diffusive sampler for the analysis of VOCs

A simple comparison is made to evaluate the relative performance of active and passive sampling methods for the analysis of volatile organic compounds (VOCs) in ambient air. The active sampling is done through a multi-sorbent bed tube (Carbotrap, Carbopack X, Carboxen 569) created in our laboratory and the passive sampling through the Radiello^® diffusive sampler specified for thermal desorption (filled with Carbograph 4). Daily duplicate samples of multi-sorbent bed tubes were taken during a period of 14 days. During the same period of time, quadruplicate samples of Radiello^® tubes were taken during 3 days, 4 days, 7 days and 14 days. The sampling was carried out indoors during the months of February and March 2010 and outdoors during the month of July 2010 in La Canonja (Tarragona, Spain). The analysis was performed by automatic thermal desorption (ATD) coupled with capillary gas chromatography (GC)/mass spectrometry detector (MSD). The analytical performance of the two sampling approaches was evaluated by describing several quality assurance parameters. The results show that the analytical performances of the methodologies studied are quite similar. They display low limits of detection, good precision, accuracy and desorption efficiency, and low levels of breakthrough for multi-sorbent bed tubes. However, the two monitoring methods produced varying air-borne concentration data for most of the studied compounds, and the Radiello^® samplers generally gave higher results. Sampling rates (Q_k) were determined experimentally, and their values were higher than those supplied by the producer. As the experimental calculation of Q_k values is generally carried out by the suppliers in exposure chambers with only the target compounds present in the air samples, as well as in concentrations dissimilar to those found in ambient air, the use of constant settled Q_k can lead to inaccurate results in complex samples.     

Laboratory and field validations of a solid-phase microextraction device for the determination of ethylene oxide

Laboratory and field evaluations were performed to validate a solid-phase microextraction (SPME) device that was used as a diffusive sampler. Hydrogen bromide (HBr) was loaded onto the carboxen-polydimethylsiloxane (CAR-PDMS) fiber for the determination of ethylene oxide (EtO) with on-fiber derivatization. For laboratory evaluations, known concentrations of ethylene oxide around the threshold limit values (TLV)/time-weighted average and specific relative humidities (RHs) were generated by syringe pumps in a dynamic generation system. The SPME diffusive samplers and the commercially available 3M 3551 passive monitors were placed side-by-side in an exposure chamber which was designed to allow measurement of face velocities, temperatures, exposing vapor concentrations, and RHs. Field validations with both SPME diffusive sampler and 3M 3551 passive monitors were also performed. The correlations between the results from both SPME device and 3M 3551 passive monitor were found to be linear (r > 0.9699) and consistent (slope approximately equal to 1.12 +/- 0.07). However, the variations of diffusion coefficients at different temperatures needs to be considered and the adjustment of sampling constant was a must when sampling at temperatures different from 25 degrees C.     

Determination of chlorinated hydrocarbons in single and multi component test gases

Summary For comparing the efficiency of active and diffusive sampling methods two diffusive samplers with different properties were used to determine chlorinated hydrocarbons (CH₂Cl₂, CHCl₃, CCl₄) in single and multi component test gas mixtures. One of the chosen diffusive samplers can also be used for active sampling.In general, good correlations of all tested methods could be observed in the direct comparison of active and diffusive sampling and in the determination of the efficiencies.During the application of active and diffusive sampling methods in multi component test gases of the analytes possible interferences could not be ascertained.     

Indoor air quality: validation and setting up quality control for determination of anions and cations in particulate matter

In recent years, the indoor air quality has been studied more frequently due to an increasing concern within the scientific community on the effects of indoor air quality upon health. The indoor air quality studies of schools have a large impact in both health and educational performance of children since they constitute a sensitive group with higher risk than adults, particularly vulnerable to pollutants due to their undeveloped airways. A total of 14 basic schools located in Lisbon city, Portugal, were selected for sampling the total particulate matter (TPM) by passive deposition into polycarbonate filters and to assess the indoor air quality. Compared to automatic samplers, this passive sampling method represents an easier and cheaper way to assess several indoor air quality environments with no interference in the classroom activities. The procedure was performed on four different campaigns during 2009–2010. The filter loads were measured by gravimetry with a 0.1-μg sensitivity balance and, afterwards, the TPM water-soluble ions content was assessed by ionic chromatography (Cl⁻, NO₃ ⁻, PO₄ ³⁻ and SO₄ ²⁻); flame absorption (Na⁺, K⁺, Mg²⁺ and Ca²⁺). The performance characteristics of the methods, namely specificity, limit of detection, limit of quantification, working range, precision and trueness were evaluated. Measurement uncertainty was expressed in terms of precision and trueness. Precision under intralaboratory reproducibility conditions was estimated from triplicate analysis. The trueness component was estimated in terms of overall recovery using the reference material SPS-NUTR WW2 Batch 107, from Spectrapure Standards, Oslo, Norway, for anions and the certified reference material CRM 1643e, from NIST, Gaithersburg, MD for cations. Measurement uncertainty of the results obtained with the methods described in this work fulfilled the relative differences (RD) defined by the anion−cation balance in the extraction solutions of the particulate matter. Target RD values were defined: RD < 0.05.     

离子色谱法测定博物馆室内空气中氨的含量

对比了Dionex IonPac CS12A和IonPac CS16两种阳离子色谱柱的分离特性,通过优化色谱条件,使两种色谱柱分别适用于被动法和主动法空气采样分析。根据铵为弱碱性阳离子发生不完全电离的特点,提出了离子色谱法测定博物馆室内空气中氨浓度的方法。绘制了低浓度和高浓度两条标准曲线,线性范围分别为0.01~0.50 mg.L-1和0.50~5.00 mg.L-1,被动法采样法得氨的检出限(3S/N)为0.9μg.L-1,回收率在97.2%~105.7%之间;主动法采样法得氨的检出限(3S/N)为1.6μg.L-1,回收率在102.8%~104.7%之间。     

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.