Internal circulation cabinets equipped with granular activated carbon (GAC) to adsorb volatile organic compounds (VOCs) are extensively utilized to store bottles containing organic solvents in Taiwanese university, college, and hospital laboratories. This work evaluates the VOC adsorption capacity of GAC with various adsorption periods for 102-2652 ppm average inlet toluene concentrations at 27 o C and relative humidity (RH) 72 ± 3%. Additionally, solid-phase microextraction (SPME) technology was employed for indicating the renew moment of GAC, and avoiding a breakthrough of toluene from adsorbents. Experimental results demonstrate that toluene adsorption capacity is linearly expressed as the natural logarithm of adsorption time (ln(t)) at a constant temperature, and the equilibrium adsorption capacity (Q e , g toluene/g GAC) for average 102-2652 ppm gaseous toluene was accurately simulated using the proposed models. The SPME fiber installed in the outlet air stream for adsorbing toluene exhausted through GAC effectively indicated the breakthrough of VOCs. The GAC-SPME operational instructions to indicate the replace time of adsorbent in the internal circulation cabinets are concluded in this study.
Gaseous toluene, ethylbenzene and o-xylene (TEX) were extracted by using the divinylbenzene (DVB) particle of 60-80 mesh as a sorbent packed in series of needle trap samplers (NTS). The feasibility of using this self-designed DVB-NTS as a diffusive time-weighted average (TWA) sampler for occupational hygiene applications was evaluated by examining extended sampling periods of 4-12 hr. Additionally, the NTS was compared in terms of extraction efficiency by simultaneously using the 75 μm Carboxen/polydimethylsiloxane-solid phase microextration (Carboxen/PDMS-SPME) fiber for sampling TEX. Experimental results indicated that, regardless of static (in a bulb) or dynamic samplings (in a flowing gas stream), the packed DVB-NTS achieved higher TEX extraction rates (ng VOCs/min) than those of 75 μm Carboxen/PDMS-SPME fiber. The decreasing rates of extracting TEX for SPME fiber were 24-34% and 28-36% as NTS performed during the sampling periods of 240 and 480 min, respectively. Typically, the maximum VOC adsorption capacities per mg DVB were measured as 5.692 μg toluene, 7.669 μg ethylbenzene and 5.199 μg o-xylene. During the sampling period of 12 hr, the DVB-NTS extracted 1600-1800 ng of individual TEX components from a continuously flowing air stream, in which the gas flow rate equals 200 mL/min. We recommend the badgelike or penlike NTS as an alternative passive sampler to the legal active sampling method 1501, National Institute of Occupational Safety and Health (NIOSH), owing to its small size and high extraction capacity of TEX.
Gaseous benzene, toluene, ethylbenzene and o-xylene (BTEX) were extracted by using the divinylbenzene (DVB) particles (mesh sizes 60-80, 80-100 and 100-120) as sorbents packed in passive needle trap samplers (NTS). This study performed feasibility tests of these self-designed DVB-NTS as diffusive time-weighted average (TWA) samplers and compared extraction efficiency with that of 100 mm polydimethylsiloxane-solid phase microextration (PDMS-SPME) fiber for sampling gaseous and particle-bound volatile organic compounds (VOCs) from burning mosquito coils. Experimental results indicated that extraction rate of NTS is a reliable index in extracting VOCs. Additionally, comparisons of the NTS in extracting BTEX mass showed the NTS packed with the smallest diameters of adsorbent particles (100-120 mesh DVB) were the most effective. The mass of gaseous BTEX extracted by 100 mm PDMS-SPME fiber were substantially lower than that extracted by DVB-NTS of all meshes for the 30-min TWA sampling of burning mosquito coils, and NTS packed with 100-120 mesh DVB adsorbed BTEX 50-120 ng BTEX. Particles clogging inside the packed phase of NTS inhibited VOC extraction performance after 3-5 samplings of burning particles, especially NTS packed with small-diameter adsorbents.
CHEMICAL SOCIETY
CONCLUSIONSThe packed DVB-NTS is a recommended passive sampler since its extracts a larger BTEX mass compared to 100 mm PDMS SPME fiber for sampling BTEX. Accord-
The needle trap sampler (NTS) has been evaluated to be a device for sampling heating products from electric-vaporization anti-mosquito mats. Based on the experimental results, this investigation assessed NTS as suitable for occupational and environmental health applications.
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