• Journal of Korean Society for Atmospheric Environment
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• v.13 no.5
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• pp.355-360
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• 1997

The atmospheric concentration of dimethylsulfide (DMS), known as the predominant volatile organic. sulfur compound, is determined at subnanogram level by a combined application of non-cryogenic preconcentration method and gas chromatography with flame photometric detection (GC/FPD). The volatile DMS in air is preconcentrated using a trapping tube containing adsorbent like Molecular Sieve 5A (or gold-coated sands). The tube is then connected to the GC/FPD system via a six-way rotary valve, thermally desorbed at 40$0^{\circ}C$, separated on OV101 column, and detected by a flame photometric detector. The DMS peak elutes at about 2.5 mins and is integrated electronically. The analytical precision, if expressed in terms of relative standard error, is around 5%. The detection limit of our GC/FPD system is ca 1 ng of DMS. Details of our analytical system are presented.

• Environmental Analysis Health and Toxicology
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• v.17 no.2
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• pp.95-107
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• 2002

This study was designed to investigate the characteristics of atmospheric concentrations of toxic volatile organic compounds (VOCs) in Korea. Target compounds included 1,3-butadiene, aromatics such as BTEX, and a number of carbonyl compounds. In this paper, as the first part of the study, the performance of sampling and analytical methods was evaluated for the measurement of selected VOCs and carbonyl compounds in the ambient air. VOCs were determined by the adsorbent tube sampling and automatic thermal desorption coupled with GC/MSD analysis, while carbonyls by the DNPH-silica cartridge sampling with HPLC analysis. The methodology was investigated with a wide range of performance criteria such as repeatability, linearity. lower detection limits, collection efficiency, thermal conditioning, breakthrough volume and calibration methods using internal standards. In addition, the sampling and analytical methods established in this study were applied to real field samples duplicately collected in various ambient environments. Precisions for the duplicate samples appeared to be comparable with the performance criteria recommended by USEPA TO-17. The overall precision of the sampling and analytical methods was estimated to be within 20 ∼ 30% for major aromatic VOCs such as BTEX, whereas the precision for major carbonyl compounds such as formaldehyde and acetaldehyde was within 10 ∼ 20% for field samples. This study demonstrated that the adsorbent sampling and thermal desorption method can be reliably applied for the measurement of BTEX in ppb levels frequently occurred in common indoor and ambient environments.

• Analytical Science and Technology
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• v.17 no.6
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• pp.496-513
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• 2004

This study was carried out to evaluate the performance of sampling and analytical methodology used for the measurement of toxic volatile organic compounds (VOCs) in the ambient air. VOCs were determined by the adsorbent tube sampling and automatic thermal desorption coupled with GC/MSD analysis. Target analytes were 33 compounds including major aromatic compounds such as BTEX, and halogenated compounds. The methodology was investigated with a wide range of different adsorbents which are commercially available and have been frequently adopted for the VOC measurement. A total of 10 adsorbents were tested in this study: 6 carbon-based adsorbents such as Carbotrap, Carbopack B, Carbosieve S-III, Carboxen 1000, Carbotrap C, Activated Charcoal; and 4 polymer-based adsorbents including Tenax, Porapak Q, Chromosorb 102, and Chromosorb 106. The sampling performance was evaluated with respect to the sampling capacity of VOCs with single-adsorbent and multiple-adsorbents methods for standard samples and field samples. As a result, the best adsorbents for single-adsorbent method in the sampling of toxic organic compounds (including benzene, toluene, xylenes etc.) appeared to be Carbotrap, Carbopack B and Tenax TA. On the other hand, Chromosorb 102, Chromosorb 106 and Porapak Q were found to be unsuitable adsorbents for VOC measurement based on thermal desorption method. Multi-adsorbent packings were evaluated with 4 carbon-based adsorbents, which classified by 3 combination sets of double adsorbents and 2 combination sets of triple adsorbents. The results indicated that the most suitable combination for toixc VOC measurements is Carbotrap C with Carbotrap. Multi-sorbents tubes packed with a strong adsorbent such as Carbosieve S-III or Carboxen 1000 were found to be relatively unsuitable for several compounds, not only owing to the effect of migration of adsorbed compounds from weaker adsorbent to stronger adsorbent, but to hydrophobic nature of the adsorbents. Therefore, it should be addressed that selection of a proper adsorbent (or combination of multi sorbents) is extremely important to obtain reliable data for the concentrations of toxic VOCs in indoor and outdoor environments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.8
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• pp.746-753
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• 2005

Adsorption chillers have been receiving considerable attentions as they are energy-saving and environmentally benign systems. In order to evaluate adsorption rates, experiments were performed in the batch type adsorption apparatus. Three types of silica gels were investigated under an assortment of experimental conditions that are representatives of the actual operating environments in the adsorber of adsorption chillers. Experimental results revealed the effects of silica gel particle size, bed temperature, and fin pitch of fin tube on the adsorption rate. The $0.25\~1.18mm$ particle size of silica gel with high adsorption rate was selected as a suitable adsorbent. The measured adsorption rate became bigger with decreasing particle size. From the comparison of adsorption rate, it is found that the fin tube has about $21\%$ higher value than that of the bare tube. The effect of heat and mass flux is found to be more significant in the fin tube than in the bare tube.

• Analytical Science and Technology
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• v.22 no.5
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• pp.395-406
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• 2009

The determination of iodine in the spent nuclear fuel and the volatile behavior during its acid dissolution have been studied by NAA(neutron activation analysis) and electron probe microanalysis (EPMA). Simulated spent fuels (SIMFUELs) were dissolved in $HNO_3$(1+1) at $90^{\circ}C$ for 8 hours. The iodine remained in a dissolver solution after dissolution, and that condensed in dissolution apparatus and trapped in the adsorbent by volatilization during the dissolution were determined, respectively. The condensed iodine was recovered by the redistillation with $HNO_3$(1+1) after transfer of the dissolver solution. The iodines in the dissolver and redistilled solution were separated by solvent extraction followed by ion exchange or precipitation method and determined by RNAA (radiochemical neutron activation analysis). The ion exchange column and filtration kit used for the isolation of iodine, which were prepared with a polyethylene tube, were used as an insert in the pneumatic tube for neutron irradiation. The iodine volatilized during the dissolution of SIMFUELs was collected in a trapping tube containing Ag-silica gel (Ag-impregnated silica gel) adsorbent, and the distribution of iodine trapped in the adsorbents were determined by EPMA. The adsorbing characteristics shown with the SIMFUELs were compared with those shown with a real spent fuel from the nuclear power plant.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.E4
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• pp.181-190
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• 2002

A novel portable device for the direct measurement of alveolar breath carbon monoxide (CO) was developed. The major components of the device include a mouthpiece, non-rebreathing two-way valve, Teflon tube, and CO dosimeter. An alveolar CO measurement can be completed within 1.5 min when using the proposed device and measurement protocol. Measurements could be read to the nearest 0.1 ppm. Humidity did not influence the CO measurements taken by the CO dosimeter, plus there were no problems associated with the recovery and carryover of CO through the device. The criterion for significance in statistical analyses was p< 0.05. The average recovery was 103 and 99% for recovery and carryover experiments, respectively. Test results using the proposed alveolar CO measurement system reflected a good reproducibility. This reproducibility was also supported by the finding that the relative standard deviations (RSDs) of the data sets were less than 7％ for the loss experiment and less than 8% for the carryover experiment. Consequently, it would appear that the proposed device can be effectively applied to measure CO levels found in breath, thereby overcoming several disadvantages associated with the conventional bag and adsorbent tube sampling methods.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.12
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• pp.660-667
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• 2013

This study presents a numerical investigation of the heat and mass transfer kinetics of a fin-tube-type adsorption bed using a two-dimensional numerical model with silica-gel and water as the adsorbent and refrigerant pair. The performance is strongly affected by the heat and mass transfer in the adsorption bed, but the details of the mass transfer kinetics remain unclear. The validity of inter-particle models used to simulate mass-transfer kinetics were examined, such as a constant pressure model and non-constant pressure model, and the valid ranges of the diffusion ratio for each model are proposed. The COP and SCP have been numerically calculated as the performance indexes according to the diffusion ratio. The constant pressure model, which is commonly used in previous research, was found to be valid only in a limited range of diffusion ratio.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.1
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• pp.104-118
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• 1995

This study was performed to evaluate factors affecting desorption of organic solvents collected on charcoal tube and to find out the optimum condition. Desorption efficiency for polar analytes was improved when several polar desorption solvents such as methanol, dimethylformamide(DMF), 2-(2-butoxyethoxy)ethanol were added to carbon disulfide($CS_2$). The best improvement was achieved when 10% dimethylformamide(DMF) in $CS_2$ was used as desorption solvent. During storage of polar analytes, recovery was greatly reduced. Especially, the recovery of cyclohexanone was decreased to 18.1 % after a month storage at $34^{\circ}C$. After two weeks storage, recovery of polar analytes was sharply decreased. Water adsorbed on charcoal interfered the recovery of polar analytes but didn't interfere that one of nonpolar solvent, toluene. When 10% DMF in $CS_2$ was used as desorption solvent, the effect of water on recovery was decreased, comparing with Desorption efficiency increased when analyte loading increased, and usage of 10% DMF in $CS_2$ decreased the loading effect. Increasing volume of desorption solvent was not effective to improve desorption efficiency of analytes when 10% DMF was used. Continuous shaking and sonication is not helpful to increase the desorption efficiency of analytes except cyclohexanone using 10% DMF. When silica gel used as adsorbent, methanol was better desorbent than dimethylsulfoxide. Analytes adsorbed on silica gel showed high recovery in low concentration and less affected by humidity. On the basis of this study, the following conclusions have been drawn. To improve the recovery of polar organic materials in air samples, it is necessary to analyze samples as soon as possible after they were collected. Otherwise, samples must be stored at low temperature. Using two components of desorption solvents, such as 10% DMF in $CS_2$, the effects of loading and humidity decreased for polar analytes such as methyl ethyl ketone and methyl isobutyl ketone. When work place has high humidity with low concentration of polar organic solvents, silica gel can be used as adsorbent, because it produces quantitative recovery for polar analytes at this condition. But it should be noted that high humidity makes breakthrough easy in silica gel samples.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.2
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• pp.209-221
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• 1996

The purpose of this study was to find a suitable cosolvent to $CS_2$ so that desorption efficiency can be improved for both polar and non-polar organic solvent mixtures collected on an activated charcoal tube. Cosolvents added to $CS_2$ include: DMF(N,N-dimethylformamide): $CS_2$ (v/v 1:99), DMF:$CS_2$(v/v 3:97), BC (butyl carbitol, 2-(2-butoxy ethoxy) ethanol):$CS_2$(v/v 1:99), and BC:$CS_2$(v/v 3:97)). The results obtained were as follows : 1. Comparing the desorption efficiency of $CS_2$ with those of $CS_2$ with 1, 3, 5 % DMF and 1, 3 % BC cosolvents for two different groups of charcoal tubes each containing 8 different polar and non-polar organic solvents with 3 different concentration levels, the desorption efficiencies of the cosolvent-added $CS_2$ increased significantly for all polar organic solvents regardless of concentration levels tested. For non-polar organic solvents, no noticeable improvement was detected except xylene and trichloroethylene. The desorption efficiency of xylene increased significantly while that of trichloroethylene increased significantly at the lowest concentration level tested. 2. Either 5 % DMF or 3 % BC was the most suitable cosolvent because the desorption efficiency for non-polar organic solvent mixtures was similar or slightly improved compared with that of $CS_2$, while those of for polar organic solvent mixtures were above 75 % except for cyclohexanone. 3. The smallest variations in desorption efficiency represented by the ratio calculated from the maximum to minimum desorption efficiency for all concentration levels tested were found when 3 % BC was used as a cosolvent. The above results indicate that the desorption efficiency of $CS_2$ particularly for polar organic solvent mixtures collected on a charcoal tube can be significantly improved by the use of cosolvents such as 5 % DMF or 3 % BC. A caution, however, is in order for selecting a cosolvent whenever the cosolvent itself is being used in the workplace or the impurities contained in the cosolvent may interfere with the analytical results. In addition, to improve desorption efficiencies for such organic solvents as cyclohexanone or ketones, it is recommended to use suitable collection and desorption media other than the traditional method of charcoal tube collection/$CS_2$ desorption.

• Analytical Science and Technology
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• v.11 no.2
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• pp.139-144
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• 1998

For the ambient monitoring of acrylamide, the adequate condition of sampling and analysis was checked. The adequate adsorbents and desorption solvents were tested. The combination of charcoal tube as a adsorbent and acetone as a desorption solvent showed 87% desorption efficiency. Flame ionization detector was used to detect acrylamide. The detection limit was 0.814 mg acrylamide in 1 L acetone. It is the equivalent concentration of 0.0203 mg acrylamide in $1m^3$ air if the volume of air collected was 40L. The permissible exposure level (PEL) of acrylamide in the workplace air recommended by Occupational Safety and Health Administration (OSHA, USA) is 0.3 mg acrylamide in $1m^3$ air. So, it is very simple and economic analytical method for acrylamide to be set in the industrial hygiene laboratories.