Badge-type diffusive sampler using 3-methyl-2-benzothiazolinone hydrazone for measuring formaldehyde in indoor air.

The evaluation of a badge-type diffusive sampler for measuring formaldehyde using 3-methyl-2-benzothiazolinone hydrazone (MBTH) was investigated. On average, the formaldehyde concentration in blanks was reduced by approximately 31% by cleaning procedures. The cleaning techniques did not significantly differ in effectiveness. The maximum sampling rate was 22.4 +/- 3.5 mL min(-1) at MBTH concentrations of 0.05%. The formaldehyde concentration in blanks did not appreciably increase over a period of about 1 month at room temperature, and was 0.36 +/- 0.03 microg, with a relative standard deviation of 8%. The diffusive sampler had good precision and accuracy for measuring formaldehyde in indoor environments. For a 24-h exposure time, the limits of detection and quantification calculated with the field blanks were 9.7 and 13.8 ppb, respectively. The minimum exposure times were calculated based on the measured and calculated limits of quantification, the sampling rate, and the atmospheric formaldehyde concentration. The capacity of the diffusive sampler with 0.5% MBTH was 3 ppm h(-1), approximately 1.5-times the capacity when the MBTH concentrations were 0.05%.     

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.     

Validation of the Willems badge diffusive sampler for nitrogen dioxide determinations in occupational environments

The Willems badge, a diffusive sampler for nitrogen dioxide, has previously been validated for ambient air measurements. This paper describes the laboratory and field validation of the Willems badge for personal sampling under working environment conditions. The mean sampling rate in the laboratory tests was 46 ml min(-1), with an RSD of 12%. No statistically significant effects on sampling rate of the sampling time, concentration of NO2 or relative humidity were found. A slightly decreased sampling rate was observed at low wind velocity. This was also confirmed during static sampling, which makes the sampler less appropriate for static sampling indoors. No back diffusion was observed. Storage of the samplers for two weeks before or after exposure did not affect the sampling rate. Our analysis is based on a modified colorimetric method, performed by FIA (flow injection analysis). This technique was compared to ion chromatography analysis. The use of ion chromatography lowered the detection limit from 11 to 2 microg m(-3) for an 8 h sample, and furthermore enabled the detection of other anions. In conclusion, the diffusive sampler was found to perform well for personal measurements in industrial environments.     

The effect of the wind velocity on the uptake rates of various diffusive samplers

This paper examines the results of experiments carried out in an exposure chamber to determine the wind effects on the performance of various diffusive sampler types commonly used for measuring gaseous pollutants in air. The resistance to wind of six diffusive samplers, two Palmes tubes, a badge with diffusion membrane, the EMD sampler and two radial diffusive samplers for different pollutants was compared in a range of velocities from 0 to 300?cm?s^?1. For all diffusive samplers tested, an increase in uptake rate was observed with increased air velocity usually following a logarithmic function. The consequences are an underestimation in the concentration measured by the diffusive samplers for low wind velocities below 30?cm?s^?1 and conversely an overestimation from 60?cm?s^?1. The magnitude of wind effects depends on diffusive sampler type and exceeds an uptake rate variation of ±20% for the axial diffusion tubes and the EMD sampler. With regard to the characteristics of each diffusive sampler, the dependence of uptake rate on wind velocity was analysed and discussed. The radial diffusive samplers for benzene and particularly the ones having a large and thick porous membrane appear to be the most effective design to minimise the influence of air velocity on passive sampling.     

Development of a Passive Sampler for Long-Term Measurements of Formaldehyde and Total Oxidants in Air

A diffusive sampling device is described that is capable of reliable measurements of formaldehyde and total oxidants (Ox = ozone + nitrogen dioxide) at sub-ppbv concentration levels in ambient air. These species are collected on silica gel particles coated with 1-methyl-1-(2,4-dinitrophenyl)hydrazine (MDNPH) and phosphoric acid. The formaldehyde hydrazone (HCHO-MDNPh) and the N-methyl-2,4-dinitroaniline (MDNA) formed are extracted with acetonitrile and determined by HPLC with UV detection at 365ánm. The measured sampling rate for HCHO, 15.0 mLmin^-1, agrees well with the theoretical value of 16.0, whilst an experimental sampling rate of 10.7 mLmin^-1 (25% lower than the calculated one) is observed for Ox. The sampling rates seem to be independent of the sampling duration up to one month. The precision of the measurements for co-located passive samplers averaged is 7.3% for HCHO and 7.2% for Ox in urban air.     

A novel approach for monitoring of cyanobacterial toxins: development and evaluation of the passive sampler for microcystins

We have investigated the ability of an integrative sampler for polar organic chemicals to sequestrate a group of common and highly hazardous cyanobacterial toxins—microcystins. In a pilot experiment, commercially available passive samplers were shown to effectively accumulate microcystins after 7 days’ exposure in the field. To find the most efficient configuration for sequestration of microcystins, four different porous membranes (polycarbonate, polyester, polyethersulfone and nylon) and two sorbents (Oasis HLB and Bondesil-LMS) were evaluated in the laboratory experiments, where samplers of different configuration were exposed to microcystins (microcystin-RR and microcystin-LR) for 14 days under steady conditions. We observed differences in sampling rates and amounts of accumulated microcystins depending on the sampler configurations. The samplers constructed with the polycarbonate membrane and Oasis HLB sorbent (2.75 mg/cm²) provided the highest sampling rates (0.022 L/day for microcystin-RR and 0.017 L/day for microcystin-LR). To the best of our knowledge, the present study is the first reporting application of passive samplers for microcystins, and our results demonstrate the suitability of this tool for monitoring cyanotoxins in water.     

“Badge-type” passive sampler for monitoring ambient ammonia concentrations

A passive “badge-type” sampling device for the determination of gaseous ammonia was developed. The collection substrate is phosphoric acid. The sampler can be used for outdoor and indoor sampling of ammonia in the concentration range from 0.05 μg/m³ to 10 mg/m³. The performance was tested in the laboratory and in the field against an annualar denuder, a filter pack and an impinger technique. The intercalibration showed that the passive sampler compares very well with active samplers (r²=0.99; k=1.05). The average reproducibility of the sampler was 8%. Hence the badge sampler is well suited for the determination of ammonia in a wide range of concentrations and particularly for application under rural background conditions. The sampling rate of the device was calculated according to a simple multi-layer model.     

Intermethod comparisons of active sampling procedures and analysis of aldehydes at environmental levels

Within the framework of a European interlaboratory exercise, the Vito facility for the generation of controlled atmospheres was used to test the suitability of four sampling techniques for priority aldehydes namely formaldehyde, acrolein, acetaldehyde, and glutaraldehyde at the ranges of 0.5 to 150 microg x m(-3). The samplers are DNPH-containing impingers, DNPH-impregnated cartridges and filters, and 2-HMP coated XAD-2 tubes. The three first DNPH samplers are to be analyzed by HPLC and the latter by GC-MS for the oxazolidine derivatives. The intermethod comparison comprises two to five sets of experiments depending on the compounds of interest. The aim of the exercise was also to assess the chemical interferences caused by ozone, nitrogen dioxide, and ammonia when using different techniques for sampling and analysis. The active DNPH method (with minor modifications such as shorter sampling time, immediate elution after sampling, and/or eventually wetting of samplers) delivered results within the 30% overall relative uncertainty for formaldehyde, acetaldehyde, and acrolein at the upper microg x m(-3) levels. However, the results suggest that the current DNPH methods for aldehydes do not comply with the 30% minimum performance criteria at the sub microg x m(-3) level. Sampling of aldehydes in the presence of ozone and NO2 interferences by using a "scrubber" cartridge appears to be beneficial to the quality of results.     

Simple analysis of volatile organic compounds (VOCs) in the atmosphere using passive samplers.

A simple analysis of volatile organic compounds (VOCs), such as benzene, toluene, m,p-xylene, and o-xylene, at low levels in the atmosphere was conducted using passive samplers. The methods were applied to analyzing the behavior and origin of VOCs in Kyoto City. The passive samplers were exposed for 7 - 14 days at sampling sites in Kyoto City and for 30 days in the mountains (Mt. Hiei and Mt. Daimonji). Shibata gas-tube samplers packed with activated carbon were used for the determination of VOCs. The absorbed VOCs were extracted into carbon disulfide (CS2) and measured by FID-GC. The determination limits and relative standard deviations for VOCs were 0.3 microg/m3 and 3%, respectively. The samplers were set up at 5 sites in March, 2001 and at 13 stations on Mt. Hiei in November, 2002. The average concentrations of ambient benzene, which were higher than the environmental criterion (3.0 microg/m3), except for those on Mt. Daimonji from March, 2001, to February, 2002, decreased to below 3.0 microg/m3 from March, 2002, to February, 2003. The decrease in ambient benzene may have been due to a decrease in the benzene content in gasoline by the end of 1999, and also by implementation of the Pollutant Release and Transfer Register (PRTR) Act in 2001.     

Development of a versatile,easy and rapid atmospheric monitor for benzene,toluene, ethylbenzene and xylenes determination in air

A new procedure for the passive sampling in air of benzene, toluene, ethylbenzene and xylene isomers (BTEX) is proposed. A low-density polyethylene layflat tube filled with a mixture of solid phases provided a high versatility tool for the sampling of volatile compounds from air. Several solid phases were assayed in order to increase the BTEX absorption in the sampler and a mixture of florisil and activated carbon provided the best results. Direct head-space-gas chromatography–mass spectrometry (HS-GC–MS) measurement of the whole deployed sampler was employed for a fast determination of BTEX. Absorption isotherms were used to develop simple mathematical models for the estimation of BTEX time-weighted average concentrations in air. The proposed samplers were used to determine BTEX in indoor air environments and results were compared with those found using two reference methodologies: triolein-containing semipermeable membrane devices (SPMDs) and diffusive Radiello samplers. In short, the developed sampling system and analytical strategy provides a versatile, easy and rapid atmospheric monitor (VERAM).     

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.     

Laboratory development and field evaluation of a new diffusive sampler to collect nitrogen oxides in the ambient air

Diffusive samplers for the determination of NO(x) and NO2 based on collection on a coated carbon paper filter have been developed. NO is first oxidized to NO2 and then collected on the reactive surface. When NO2 and NOx samplers are exposed simultaneously, NO can be calculated by difference. The sampler has been derived from a Palmes design as recently modified by Bertoni et al. for the determination of BTX (benzene, toluene, xylenes). Laboratory tests were conducted in controlled atmosphere to evaluate linearity, uptake rate, face velocity effects, sample stability, influence of relative humidity, precision and accuracy. The samplers are capable of reliable measurements of the two species at common levels of a polluted atmosphere in urban settings yielding average concentration levels over 1 month and beyond.The uptake rate of NO2 was found to be 11.7 mL/min in a very good agreement (within 5%) with the value calculated from theory. The measured uptake rate for NO(x) was determined in experiments involving sampling at different concentration levels in comparison to chemiluminescence (CL) measurements. The precision of the measurements for co-located passive samplers was better than 5%. The accuracy of the data collected is within +/-20% of the actual value measured by CL. The laboratory and field results show that the NO(x) and NO2 samplers meet the data quality goal requested by the first EU Directive 1999/30/EU for these pollutants.     

Evaluation of denuder sampling for a mixture of three common gaseous diisocyanates

A denuder sampler has been evaluated for a mixture of three gaseous diisocyanates, i.e. toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). Sampling was performed at a total concentration of diisocyanates close to the Swedish occupational exposure limit (OEL), which is 10 ppbv (69-92 microg m(-3)), for a 5-min period. The denuder tube was coated with a chemosorptive stationary phase consisting of SE-30 (polydimethylsiloxane) and the derivatising reagent dibutylamine (DBA). It was shown that the denuder has a collection efficiency for HDI and IPDI comparable to that of an impinger method, while sampling of TDI resulted in an 8% lower concentration. Both short-term (15 min) and long-term (8 h) sampling periods were shown to yield reproducible results. For 8-h measurements, a sampling flow rate of 5 mL min(-1) was shown to be suitable for the investigated concentration range, i.e. 10-100 ppbv (69-921 microg m(-3)). A flow rate of 25 mL min(-1) or higher resulted in breakthrough after 8 h due to chromatography of the compounds in the adsorbent. The limit of detection (LOD) for the air sampling method is nearly 500 times lower than the OEL. The denuder tubes can be prepared at least 10 days prior to sampling without degradation of performance. Furthermore, they can be stored up to 6 days in a freezer after sampling without significant loss of analytes.     

Development and field evaluation of a new diffusive sampler for Hydrogen Sulphide in the ambient air

A diffusive sampler for the determination of hydrogen sulphide (H₂S) based on collection on a paper filter coated with silver nitrate followed by optical densitometric determination of the metal sulphide was developed. Laboratory tests were conducted in controlled atmosphere to evaluate linearity, uptake rate, face velocity effects, sample stability, influence of relative humidity and of interferents, precision and accuracy. The measured uptake rate for H₂S was determined in experiments involving sampling at different concentration levels in comparison to a wet standard colorimetric technique. The precision of the measurements for co-located passive samplers was lower than 15%. The accuracy of the data collected is within 20% of the actual value measured by the wet method. The sampler is capable of reliable measurements of H₂S at common levels of a polluted atmosphere in urban settings yielding average concentration levels over one month and beyond. Diffusive sampling can be adopted to analyse in detail the temporal and spatial trends of H₂S concentration in ambient air and in specific historic buildings or in museums. Figure At the end of sampling cap #2 is removed and optical density is measured     

Mercury and organotin compounds monitoring in fresh and marine waters across Europe by Chemcatcher passive sampler

Several field trials have been carried out to assess the performance of the passive sampler Chemcatcher as aquatic monitoring technology for inorganic mercury and the organotin pollutants monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in different types of waters across ten locations in Europe. Two version of the sampler were used. One for mercury that consists on 47?mm Empore? disks of iminodiacetic chelating groups as the receiving phase overlaid by a diffusion membrane of polyethersulphone; and other for organotin compounds comprising a C₁₈ disk and a cellulose acetate membrane. Both membranes were held in a disposable polycarbonate body. The two samplers were calibrated in the laboratory in a previous work to estimate the pollutant concentration. For field sampling, the samplers were deployed for 14 days. In parallel spot samples were periodically collected during the deployment period for comparison purposes. No significant biofouling on the samplers was observed for the locations monitored. In general, water concentrations estimated by Chemcatcher were lower than those found in spot water samples due to the device only collected the soluble bioavailable fraction of target pollutants. However, the pre-concentration capability of Chemcatcher allowed the determination of the tested pollutants at levels where spot sampling fails, even in difficult water bodies such as sewage treatment plants. These advantages lead to consider this emerging methodology as a complementary tool to traditional spot sampling.     

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.     

Polydimethylsiloxane-based permeation passive air sampler. Part I: Calibration constants and their relation to retention indices of the analytes

A simple and cost effective permeation passive sampler equipped with a polydimethylsiloxane (PDMS) membrane was designed for the determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air. Permeation passive samplers have significant advantages over diffusive passive samplers, including insensitivity to moisture and high face velocities of air across the surface of the sampler. Calibration constants of the sampler towards 41 analytes belonging to alkane, aromatic hydrocarbon, chlorinated hydrocarbon, ester and alcohol groups were determined. The calibration constants allowed for the determination of the permeability of PDMS towards the selected analytes. They ranged from 0.026 cm² min⁻¹ for 1,1-dichloroethylene to 0.605 cm² min⁻¹ for n-octanol. Further, the mechanism of analyte transport across PDMS membranes allowed for the calibration constants of the sampler to be estimated from the linear temperature programmed retention indices (LTPRI) of the analytes, determined using GC columns coated with pure PDMS stationary phases. Statistical analysis using Student's t test indicated that there was no significant difference at the 95% probability level between the experimentally obtained calibration constants and those estimated using LTPRI for most analyte groups studied. This correlation allows the estimation of the calibration constants of compounds not known to be present at the time of sampler deployment, which makes it possible to determine parameters like total petroleum hydrocarbons in the vapor phase.     

Performance of two different types of passive samplers for the GC/ECD-FID determination of environmental VOC levels in air

Two types of passive samplers differing in their geometry (OVM 3500 by 3M, ORSA 5 by Dräger) were compared with respect to their suitability for typical environmental indoor and outdoor VOC concentrations. Benzene, toluene, o-, m-, p-xylene, ethylbenzene, tetrachloroethene, trichloroethene, nonane and ethyl acetate were representatively analyzed by dual-column capillary gas chromatography with tandem ECD-FID detection. There was a good correlation between the results obtained with OVM 3500 and ORSA 5 monitors indicating that both monitors can be used for this kind of application. The ratio between the results for indoor air sampling with OVM 3500 and ORSA 5 monitors was between 0.89 and 1.14 showing no systematic variation. For outdoor air sampling the ratio was between 1.06 and 1.26 indicating that the results obtained with OVM 3500 monitors were slightly higher. Reproducibility was slightly better when using ORSA 5 monitors. But, due to the higher sampling rates which are a result of the larger cross-sectional area, signal-to-noise ratios obtained with OVM 3500 monitors were between six to nine times higher than those of ORSA 5 samplers. Blank values of the unexposed samplers were comparable for both sampler types. As a consequence, detection limits were by a factor of 1.5 to 4 better for OVM 3500 monitors.     

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%.     

Trace analysis of airborne aromatic isocyanates and related aminoisocyanates and diamines using high-performance liquid chromatography with ultraviolet and electrochemical detection

A high-performance liquid chromatographic method was developed for trace analysis of complex air mixtures containing 2,6- and 2,4-toluenediisocyanates and related aminoisocyanates and diamines. The accuracy was tested at isocyanate concentrations of 2-1000 microg/m3 in air. The method is based on derivatization in the sampling step of isocyanate functions to corresponding urethane groups, with alkaline ethanol as the sampling and reacting medium. The derivatives formed, toluenediurethanes and tolueneaminourethanes, and unreacted diamines were detected by UV or electrochemically, the electrochemical detection being one order of magnitude more sensitive. Using an enrichment column, detection limits of ca. 0.05 pg/microl were obtained with electrochemical detection at a potential of 950 mV, which corresponds to air concentrations of 0.1 microg/m3 with 5 min sampling time at a rate of 11/min. The precision in the measurements were ca. 4% at concentrations of 6 microg/m3. A field measurement was performed concerning flame lamination of toluenediisocyanate-based polyurethane and cloth. Isocyanates, aminoisocyanates and diamines were found at air concentrations of 1-100 microg/m3.