Development of active and diffusive sampling methods for determination of 3-methoxybutyl acetate in workplace air

Monitoring of the workplace concentration of 3-methoxybutyl acetate (MBA), which is used in printer's ink and thinner for screen-printing and as an organic solvent to dissolve various resins, is important for health reasons. An active and a diffusive sampling method, using a gas chromatograph equipped with a flame ionization detector, were developed for the determination of MBA in workplace air. For the active sampling method using an activated charcoal tube, the overall desorption efficiency was 101%, the overall recovery was 104%, and the recovery after 8 days of storage in a refrigerator was more than 90%. For the diffusive sampling method using the 3M 3500 organic vapor monitor, the MBA sampling rate was 19.89 cm(3) min(-1). The linear range was from 0.01 to 96.00 microg ml(-1), with a correlation coefficient of 0.999, and the detection limits of the active and diffusive samplers were 0.04 and 0.07 microg sample(-1), respectively. The geometric mean of stationary sampling and personal sampling in a screen-printing factory were 12.61 and 16.52 ppm, respectively, indicating that both methods can be used to measure MBA in workplace air.     

A diffusive sampling device for the determination of formaldehyde in air using N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) as reagent

A new method utilizing the diffusive sampling of formaldehyde in air has been developed. Formaldehyde is sampled with the use of a glass fiber filter impregnated with N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) and phosphoric acid. The formaldehyde hydrazone formed is desorbed from the filter with acetonitrile and determined by high-performance liquid chromatography (HPLC) with UV/visible detection at 474 nm. The sampling rate was determined to be 24.7 mL min-1 with a relative standard deviation of 7% for 48 experiments. The measured sampling rates were not dependent on the formaldehyde concentration (0.1-1.0 mg m-3), sampling time (15-482 min) or relative humidity (20-85%). The detection limit was 70 micrograms m-3 for a 15 min sampling period and 2 micrograms m-3 for an 8 h sampling period.     

Evaluation of two adsorbents for diffusive sampling and thermal desorption-gas chromatographic analysis of monoterpenes in air

Tube type samplers with two different adsorbents, Chromosorb 106 and Tenax TA, were evaluated by laboratory experiments and field tests for simultaneous diffusive sampling of alpha-pinene, beta-pinene and delta 3-carene and subsequent thermal desorption-gas chromatographic analysis. No statistically significant effects of exposure time, concentrations of monoterpenes or relative humidity were found for samplers with Chromosorb 106 when running a factorial design, with the exception of the adsorption of delta 3-carene, for which some weak effects were noted. Samplers with Tenax TA were affected by the sampling time as well as the concentration for all terpenes, with a strong interaction effect between these two factors. The terpenes showed good storage stability on both adsorbents. No effect of back-diffusion was noted when using Chromosorb 106, while Tenax TA showed some back-diffusion effects. The uptake rates, in ml min-1, for the terpenes on Chromosorb 106 were 0.36 for alpha-pinene, 0.36 for beta-pinene and 0.40 for delta 3-carene. The corresponding average values on Tenax TA were 0.30 for alpha-pinene, 0.32 for beta-pinene and 0.38 for delta 3-carene. The field validation proved that diffusive sampling on Chromosorb 106 agreed well with pumped sampling on charcoal for stationary samples, while the personal samples indicated a discrepancy of 25% between Chromosorb 106 and charcoal samples. Tenax TA generally gave lower results than Chromosorb 106 in all field samples. Samplers packed with Chromosorb 106 could be used to monitor terpene levels in workplaces such as sawmills. The major advantages with this method are the sampling procedure, which is simple to perform compared to other techniques, the easily automated analysis procedure and the possibility to reuse the samplers.     

Performances and application of a passive sampling method for the simultaneous determination of nitrogen dioxide and sulfur dioxide in ambient air

The performances and applicability of a diffusion tubesampler for the simultaneous measurements of NO₂ andSO₂ in ambient air were evaluated. SO₂ andNO₂are collected by the passive sampler using triethanolamine astrapping agent and are determined as sulphate and nitrite withion chromatography. The detection limit (2.3 g m^-3 ofNO₂ and 4.2 g m^-3 of SO₂ for two weekssampling) is adequate for the determination of concentrationsin urban and industrial areas. Precision of the method as RSDis in mean 5% for NO₂ and 12% for SO₂ at theconcentration levels in urban areas. Calibration of the methodwas performed in the field conditions by comparison between theresponses of sampler and the concentrations measured by thecontinuous monitors. High degree of linearity (correlationcoefficients > 0.8) is found between the passive sampler tubeand the continuous monitor data for both NO₂ and SO₂.To reduce the wind velocity influence on passive sampling ofdiffusion tubes, a protective shelter was tested in this study.The overall uncertainty of one measure for the optimised methodis estimated at 5 g m^-3 for NO₂ and 6g m^-3 for SO₂. Suitability of this passivesampling method for air pollution monitoring in urban areas wasdemonstrated by the results shown in this paper on a campaigncarried out in the French agglomeration.     

Development of a solid phase microextraction (SPME) method for the sampling of VOC traces in indoor air

Solid-phase microextraction (SPME) was studied for the measurement of volatile organic compounds (VOCs) in indoor air. An adsorptive PDMS/Carboxen fibre was used and an analytical methodology was developed in order to overcome competitive adsorption. Kinetics and adsorption isotherms were investigated for different sample volumes and model compounds. In order to evaluate competitive adsorption on the fibre, these compounds were studied alone and in mixture. From the results obtained, the operating conditions allowing co-adsorption of the target compounds were determined: the air sample is enclosed in a 250 mL glass bulb where the SPME fibre is exposed until adsorption equilibrium. This procedure was combined with GC/MS analysis for the identification and quantification of VOCs in indoor air. The performances were determined by using a standard gas containing 10 VOCs representative of indoor environments (acetaldehyde, acetone, BTX, alpha-pinene, trichloroethylene, alkanes). The detection limits were determined in single ion monitoring mode and for a signal to noise ratio of 3. Except acetaldehyde (6 microg m(-3)), they are all below 0.5 microg m(-3). Calibration curves are linear up to 10 micromol m(-3) for all the compounds with good correlation coefficients (above 0.99). The reproducibility ranges from 6 to 12% according to the compound. The methodology was then applied to the comparison of the VOCs content in classrooms of two different schools.     

A passive sampling method to determine ammonia in ambient air

Ambient ammonia concentrations, mainly originating from agricultural activities, have increased in the last few decades in Europe. As a consequence, critical loads on oligotrophic ecosystems such as forests and mires are greatly exceeded. Monitoring of ambient ammonia concentrations is necessary in order to investigate source-receptor relationships. Measuring ambient ammonia concentrations continuously with high time resolution is very expensive and cost-efficient systems are required. Where time resolution is of minor importance, several cost-effective systems, mainly dry denuder and passive samplers, can be applied. In this paper the Zürcher passive sampler, a diffusive sampling system, is presented. It is a Palmes type sampler with an acidic solution as absorbent and is easy to handle. It was tested at 46 sites in Switzerland over one year. The average concentration in ambient air was 2.5 microg m(-3) +/- 0.4 microg m(-3). The average of the blank values were 0.21 microg m(-3). The detection limit (double the standard deviation of the blank values) was 0.36 microg m(-3). Three passive samplers were exposed at each site and each period. The mean standard deviation of these triplicate measurements was 9.5%. Compared with a discontinuous tubular denuder system and a continuous annular denuder system, the deviation was less than 10%. The Zürcher passive sampler is a useful and cost-efficient tool to determine long-term average ammonia concentrations (one- to four-week periods) in ambient air for mean concentrations above 1 microg m(-3).     

Diffusive sampling of methyl isocyanate using 4-nitro-7-piperazinobenzo-2-oxa-1,3-diazole (NBDPZ) as derivatizing agent

A diffusive sampling method for the determination of methyl isocyanate (MIC) in air is introduced. MIC is collected using a glass fiber filter impregnated with 4-nitro-7-piperazinobenzo-2-oxa-1,3-diazole (NBDPZ). The urea derivative formed is desorbed from the filter with acetonitrile and analyzed by means of high-performance liquid chromatography (HPLC) using fluorescence detection (FLD) with lambdaex = 471 nm and lambdaex = 540 nm. Additionally, a method was developed using tandem mass spectrometric (MS-MS) detection, which was performed as selected reaction monitoring (SRM) on the transition [MIC-NBDPZ + H]+ (m/z 307) to [NBDPZ + H]+ (m/z 250). The diffusive sampler was tested with MIC concentrations between 1 and 35 microg m(-3). The sampling periods varied from 15 min to 8 h, and the relative humidity (RH) was set from 20% up to 80%. The sampling rate for all 15 min experiments was determined to be 15.0 mL min(-1) (using HPLC-FLD) with a relative standard deviation of 9.9% for 56 experiments. At 80% RH, only 15 min sampling gave acceptable results. Further experiments revealed that humidity did not affect the MIC derivative but the reagent on the filter prior to and during sampling. The sampling rate for all experiments (including long term sampling) performed at 20% RH was found to be 15.0 mL min(-1) with a relative standard deviation of 6.3% (N = 42). The limit of quantification was 3 microg m(-3) (LC-MS-MS: 1.3 microg m(-3)) for 15 min sampling periods and 0.2 microg m(-3) (LC-MS-MS: 0.15 microg m(-3)) for 8 h sampling runs applying fluorescence detection.     

沥青烟中苯并(a)芘的等速采样与监测

新的大气污染综合排放标准对沥青及碳素制品生产和加工制定了沥青烟和苯并(a)芘的排放标准,然而空气和废气监测分析方法没有给出沥青烟气中苯并(a)芘的分析方法.为此,用色谱固定液滤筒及新设计的富集器等速采样,进行沥青烟苯并(a)芘的分析,为执行新的大气污染综合排放标准提供了实用技术.     

Evaluation of the best compromise between the urban air quality monitoring resolution by diffusive sampling and resource requirements

The need to collect data representative of overall urban pollution is all-important in order to monitor the population exposure. High spatial resolution monitoring using diffusive samplers allows studying of the urban pollutant distribution, thus enabling deeper investigation of their generation and diffusion mechanisms. Nevertheless, such a monitoring campaign has a certain cost. In this study we point out how to find the best compromise between the number of necessary measurements and the affordable costs for monitoring campaigns. We also describe an innovative method for the proper design of a fixed urban monitoring network by means of preliminary high spatial resolution campaigns using diffusive samplers. Four European capital cities (Dublin, Madrid, Paris and Rome) were monitored six times, each time for seven days. Benzene, toluene, ethylbenzene, xylenes (BTEX) and NO(2) concentrations were measured at 146 sites in Dublin, 293 in Madrid, 339 in Paris and 290 in Rome. Multiscale grids have been drawn which ranged in mesh size from 500 m to 2 km. The statistical processing of data produced a twofold result: the creation of isoconcentration maps with geostatistical procedures, and an algorithm aimed at locating the minimum number of sampling sites where the fixed monitoring stations should be placed. Average urban levels estimated on the basis of these selected sites differ by less than 8% from those calculated on the whole populations of the sampled points. The aim of this work is to investigate how far the resolution of a monitoring campaign of urban pollution by diffusive sampling can be reduced, thus making the monitoring less expensive in terms of human and financial resources, while preserving the same quality of the results that could be achieved with a higher resolution. We found that there is no significant loss of information when the resolution of the monitoring grid for BTEX is lowered to a mesh size of 1.85 km, that is a sampling site each 3.4 km(2), and that the minimum number of sampling sites to be used is N = 0.29 A, where A is the urban surface to be monitored (in km(2)). As the spatial distribution of NO(2) is less sensitive to the distance from the emission source than that of BTEX, this relationship could be retained as a valid lower limit for the mesh grid size also for NO(2) monitoring.     

Development of a personal monitoring method for nitrogen dioxide and sulfur dioxide with Sep-Pak C18 cartridge sampling and ion chromatographic determination

Personal monitoring methods for the determination of hourly integrated concentrations of NO2 and SO2 in ambient air have been developed. Triethanolamine (TEA)-impregnated C18 Sep-Pak cartridges were used to collect NO2 and SO2 simultaneously. After sampling, NO2 and SO2 as their nitrite, nitrate, sulfite and sulfate analogues were stripped from the cartridges with a solution of 5% methanol in distilled, deionized water (DDW) and then determined by ion chromatography. Laboratory tests were conducted to evaluate the sampling rate, collection and recovery efficiencies, breakthrough volumes, absorption capacity, interference and sample stability on the cartridge during storage. NO2 and SO2 detection limits of 0.3 and 0.4 ppb respectively for 1 h samples were obtained. Recoveries for both NO2 and SO2 exceeded 85%.     

Evaluation of a simultaneous sampling method of PAHs, PCDD/Fs and dl-PCBs in ambient air

The Stockholm Convention on Persistent Organic Pollutants (POPs) was signed in May 2001 by 127 countries. Currently, 12 substances are regulated by the convention, and the work on finding new candidate chemicals to the convention has started. Among these 12 substances, dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are the objects of this study. There are no European standard methods for the simultaneous determination of these microorganic compounds, together with polycyclic aromatic hydrocarbons (PAHs) in ambient air--they must be referred to three different methods developed by the U.S. Environmental Protection Agency (EPA). The quali-quantitative analysis of these microorganic pollutants is an important challenge due to the low concentrations at which they may be present. In this study, the development of a simplified, alternative, fast and affordable sampling method for the determination of PAHs, PCDDs, PCDFs and PCBs in ambient air was performed. The sampling time was extended from 24 h to 7 d in order to enrich the sample, to fall within the instrumental limits of detection and to reduce the number of samples to be processed and, therefore, errors that may arise. First of all, experiments with labelled standards were conducted in the research area of Montelibretti (rural station, which is sited about 20 km northeast of Rome), with the purpose of optimizing sampling efficiency. Finally, the method was applied to the analysis of these compounds in the air of a suburban area with small industrial plants in order to evaluate the feasibility of the proposed sampling method system, by comparing concentrations of native compounds acquired during simultaneous daily and weekly sampling.     

The determination of carbonyl compounds in air using a robotic sampling preparation system integrated to a gas chromatograph with a nitrogen-phosphorus detector

A totally automated solid phase extraction gas chromatography procedure was developed for the sampling and analysis of carbonyl compounds in air. In this system, two PrepStation modules were used, one for the preparation and elution of 2,4-dinitrophenylhydrazine silica cartridges, and the other for air sampling. The sample collected by the sampling module was eluted to an autosampler vial in the PrepStation module and then transferred to the gas chromatograph for analysis via a robotic arm. The sampling module was modified to enable air sampling via an external pump. A typical run by this technique required 142 min, 100 min for air sampling and 42 min for the other operations, including a GC analysis time of 25 min. Recoveries of at least 85% were obtained for all compounds studied. The detection limits for formaldehyde, acetaldehyde and acetone were 2.2, 2.7 and 2.2 ppbv, respectively. All operations, including the conditioning of the cartridges, were performed without any intervention from the analyst.     

Solvent-free sampling with di-n-butylamine for monitoring of isocyanates in air

The solvent-free sampler for airborne isocyanates consisted of a polypropylene tube with an inner wall coated with a glass fibre filter, coupled in series with a 13 mm glass fibre filter. The filters were impregnated with reagent solution containing equimolar amounts of di-n-butylamine (DBA) and acetic acid. Air sampling was performed with an air flow of 0.2 l min(-1). The formed isocyanate-DBA derivatives were determined using liquid chromatography and tandem mass spectrometry. The sampler was investigated in regard to collection principle and extraction of the formed derivatives with good results. The possibility to store the sampler before sampling and to perform long-term sampling was demonstrated. Field extraction of the sampler was not necessary, as there was no difference between immediately extracted samples and stored ones (2 days). In comparative studies, the sampler was evaluated against a reference method, impinger-filter sampling with DBA as reagent. The ratios between the results obtained with the sampler and the reference in a test chamber at a relative humidity (RH) of 45% was in the range of 83-109% for isocyanates formed during thermal decomposition of PUR. At RH 95%, the range was 72-101% with the exception of isocyanic acid. In two field evaluations, the ratios for fast curing 2,4'- and 4,4'-methylene bisphenyl diisocyanate (MDI) was in the range 81-113% and for the 3-ring MDI the range was 54-70%. For the slower curing 1,6-hexamethylene diisocyanate (HDI) and HDI isocyanurate, the ratios were in the range 78-145%. In conclusion, the solvent-free sampler is a convenient alternative in most applications to the more cumbersome impinger-filter sampler.     

Long-term measurement of volatile organic compounds in ambient air by canister-based one-week sampling method

A canister-based 1 week sampling method using a mechanical flow controller and a 6 L fused-silica-lined canister was evaluated for the long-term measurement of 47 VOCs in ambient air at pptv (volume/volume) to ppbv levels by use of a three-stage preconcentation method followed by GC-MS analysis. The GC conditions were initially optimized for complete separations of several pptv-level VOCs (e.g. vinyl chloride, 1,3-butadiene, acrylonitrile, 1,2-dichloroethane and chloroform) in ambient air because the selected ions are easily interfered with by coexisting C4-, C5-hydrocarbons and analytes presented at ppbv levels. Thirty-four VOCs determined by the 1 week and 24 h sampling method in December 16-22 (2002) had concentrations of 6.0-15000 pptv per compound. Concentrations of 28 VOCs (including polar VOCs (e.g. methyl isobutyl ketone and butyl acetate)) obtained by the method were approximately equal to the mean values calculated from 24 h sampling (< +/- 10% deviation). Six VOCs that had low concentrations of 6.0-43 pptv showed more than +/- 10% deviation. Thirteen VOCs were not detected during the entire sampling period. The effect of relative humidity or ozone for the specific VOCs (e.g. MIBK, butyl acetate, vinyl chloride, 1,3-butadiene and styrene) was negligible.     

固相萃取净化高效液相色谱法测定环境污染空气中的甲磺隆

采用自制 Florisil固相萃取预处理小柱浓缩、净化 高效液相色谱法 ,测定了环境污染空气中 (气体样、TSP样 )及地面扬尘中痕量甲磺隆含量 ,结果满意。空气和地面扬尘中甲磺隆的最低检测浓度分别为 :2× 1 0 - 5mg m3 、2× 1 0 - 3mg kg;不同添加浓度的回收率分别为空气中 80 5 %～ 96 5 % ,地面扬尘中 89 3%～ 1 0 5 1 %。     

填充柱气相色谱法测定空气和废气中的乙酸

在用蒸馏水吸收空气或废气中的乙酸后,采用5%PEG20M+0.5%H3PO4chromo-sorbHP80～100目2m×2mm玻璃填充柱,GC直接进样测定蒸馏水中的乙酸,方法简便、快捷,变异系数为2%～5%,加标回收率为85%～106%,最低检出浓度为0.16mg/m3。     

24 h diffusive sampling of toxic VOCs in air onto Carbopack X solid adsorbent followed by thermal desorption/GC/MS analysis-laboratory studies

Diffusive sampling of a mixture of 42 volatile organic compounds (VOCs) in humidified, purified air onto the solid adsorbent Carbopack X was evaluated under controlled laboratory conditions. The evaluation included variations in sample air temperature, relative humidity and ozone concentration. Linearity of samples with loading was examined both for a constant concentration with time varied up to 24 h and for different concentrations over 24 h. Reverse diffusion and its increase with accumulation of sample were determined for all compounds. Tubes were examined for blank levels, change of blanks with storage time, and variability of blanks. Method detection limits were determined based on seven replicate samples. Based on this evaluation, 27 VOCs were selected for quantitative monitoring in the concentration range from approximately 0.1 to 4 ppbv. Comparison results of active and diffusive samples taken over 24 h and under the same simulated ambient conditions at a constant 2 ppbv were interpreted to estimate the effective diffusive sampling rates (ml min(-1)) and their uncertainties and to calculate the corresponding diffusive uptake rates (ng ppmv(-1) min(-1)).     

SPME-based air sampling method for inhalation exposure assessment studies: case study on perchlorethylene exposure in dry cleaning

Exposure to perchlorethylene, especially for dry cleaning workers and for people living near dry cleaning shops, could lead to several diseases and disorders. This study examines the value of solid-phase microextraction (SPME) for sampling perchlorethylene in the atmosphere of dry cleaning shops. Carboxen/polydimethylsiloxane (CAR/PDMS) in 0.5-cm retracted mode was selected. There were no significant differences between sampling rates at different temperatures (range of 20 to 30 °C) and air velocities (2 to 50 cm/s). On the opposite, relative humidity (RH) had a significant effect on sampling rates. Method reproducibility was realized in the laboratory and field conditions and was 6.2 % and 7 to 11 %, respectively. Repeatability was also determined as 8.9 %. Comparison of the results according to the American Industrial Hygiene Association exposure assessment strategy showed the SPME sampler yields more conservative results in comparison with traditional standard method.