• 분석과학
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• 제30권5호
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• pp.240-251
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• 2017

1,1,1,2-수소불화탄소(HFC-134a)는 에어컨에 주로 사용되는 냉매로, 최근 온실가스로 규제되어 정제를 통한 재사용 방법이 권장되고 있다. 폐냉매의 재사용 기준 평가를 위해서는 폐냉매에 존재하는 미량 성분의 정량분석이 매우 중요하다. 본 연구에서는 표준 물질이 없어서 정량화하기 어려웠던 C, H, Cl, F가 포함된 미량 성분들을 GC/AED (gas chromatograph-atomic emission detector)를 이용하여 정량분석하였다. 이를 위하여 GC/MSD (mass selective detector)를 통한 정성분석을 선행하였다. 또한 성분의 원자 수와 비례하여 반응하는 AED의 특성을 조사하기 위하여, 탄화수소 혼합 표준물질을 이용하여 선형성을 확인하였다. 시료 중 C, H, Cl, F가 포함된 미량 성분의 정성 분석 결과, 주성분인 HFC-134a와 유사 냉매류들을 포함한 총 15 개의 성분이 검출되었다. MSD 결과를 토대로 AED를 이용한 미량 성분들을 정량 분석한 결과, 한 시료는 $CHClF_2$ 성분($45438.38{\mu}mol/mol$), 또 다른 시료는 $C_2H_2ClF_3$ 성분($1311.47{\mu}mol/mol$)이 가장 높은 몰분율을 나타냈다. 본 연구에서는 이 분석법을 기반으로 하여, 표준 물질이 존재하지 않아 정량화하기 어려운 복합 성분들의 정성 및 정량 분석의 확장 적용이 가능할 것으로 보인다.

• Journal of Mechanical Science and Technology
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• 제20권12호
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• pp.2284-2291
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• 2006

The present study investigates gas residence time and mixing characteristics for various swirl numbers generated by injection of secondary air into a lab-scale cylindrical combustor. Fine dust particles and butane gas were injected into the test chamber to study the gas residence time and mixing characteristics, respectively. The mixing characteristics were evaluated by standard deviation value of trace gas concentration at different measurement points. The measurement points were located 25 mm above the secondary air injection position. The trace gas concentration was detected by a gas analyzer. The gas residence time was estimated by measuring the temporal pressure difference across a filter media where the particles were captured. The swirl number of 20 for secondary air injection angle of 5$^{\circ}$ gave the best condition: long gas residence time and good mixing performance. Numerical calculations were also carried out to study the physical meanings of the experimental results, which showed good agreement with numerical results.

• 한국진공학회지
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• 제15권1호
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• pp.24-30
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• 2006

광학공동 적분 투과 분광법(integrated cavity output spectroscopy, ICOS)은 파장가변 레이저와 광학공동을 이용해 미량기체의 절대 밀도를 고감도로 측정할 수 있는 실시간 흡수 분광계측 기법이다. 이 기법은 압전 소자를 이용해 길이가 변조되는 고 피네스(high finesse) 파브리-페로 공동(Fabry-Perot cavity)을 공명 투과하는 연속파 파장 변조 레이저의 적분 출력으로 부터 공동 내부 시료의 분광 흡수량을 측정하는 원리를 이용한다. 본 연구에서는 764,7nm 파장 근처에서 파장이 변조되는 외부 공진기 반도체 레이저를 광원으로 사용하고, $99.997\%$의 높은 반사율을 갖는 거울로 구성된 파브리-페로 공동을 이용해 파장에 따른 투과 감쇠 신호를 발생시키는 실험 장치를 구성하였다. 산소 기체에 대한 측정 실험을 수행한 결과, 최소 흡수계수 $8.45\times10^{-8}cm^{-1}$에 해당하는 미량기체 밀도를 측정할 수 있는 성능을 얻었다.

• 분석과학
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• 제36권5호
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• pp.205-215
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• 2023

In the present study, an analytical method was proposed for detecting trifluralin in aquatic products at trace concentrations. The method employed QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) and gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) as the sample preparation and measurement, respectively. The effect of the aqueous phase volume used in the QuEChERS was demonstrated, and the ratio of 10:10 (mL) between water and acetonitrile phase was used for 5 g of sample. Besides, dSPE using C18 and primary-secondary amine (PSA) was applied to remove the potential interferences from the food matrices, indicating no remarkable analyte loss. The linear range was built up from 0.50 ㎍ L^-1 to 3.0 ㎍ L^-1 (R² = 0.9993). Other criteria, i.e., repeatability (RSD_r = 0.86-1.96 %), reproducibility (RSD_R = 1.09-2.01 %), and recovery (over 90 %), were in accordance with Appendix F of AOAC (2016) for method performance. Although no trifluralin was detected for the commercial samples (fish, shrimp, and breaded shrimp), the spiked samples performed favorable recoveries and precision.

• Journal of Korean Society for Atmospheric Environment
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• 제21권E3호
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• pp.75-85
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• 2005

A mathematical sensitivity analysis of the flow-through dynamic flux chamber technique, which has been utilized usually for various trace gas flux measurement from soil and water surface, was performed in an effort to provide physical and mathematical understandings of parameters essential for the NO flux calculation. The mass balance equation including chemical reactions was analytically solved for the soil NO flux under the steady state condition. The equilibrium concentration inside the chamber, $C_{eq}$, was found to be determined mainly by the balance between the soil flux and dilution of the gas concentration inside the chamber by introducing the ambient air. Surface deposition NO occurs inside the chamber when the $C_{eq}$ is greater than the ambient NO concentration ($C_{0}$) introducing to the chamber; NO emission from the soil occurs when the $C_{eq}$ is less than the ambient NO concentration. A sensitivity analysis of the significance of the chemical reactions of NO with the reactive species (i.e. $HO_{2},/CH_{3}O_{2},/O_{3}$) on the NO flux from soils was performed. The result of the analysis suggests that the NO flux calculated in the absence of chemical reactions and wall loss could be in error ranges from 40 to $85\%$ to the total flux.

• 한국대기환경학회지
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• 제23권2호
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• pp.191-202
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• 2007

We developed an in-situ analyzer to understand the HONO levels in indoor environments. The in-situ measurement system utilizes a diffusion scrubber and luminol chemiluminescence to measure the HONO concentration with time resolution of 4-minute. Concentrations of NO, $NO_{2}$, and HONO were determined at an indoor air of an apartment for 9 days using the developed in-situ analyzer. Indoor HONO concentrations were highly elevated when a gas range was operated. Enhancements of the indoor NO, $NO_{2}$, and HONO concentrations during combustion indicate that the observed indoor HONO was formed by direct emission. In addition to the direct emission, the indoor HONO was partially generated from heterogeneous reactions of $NO_{2}$ on indoor surfaces, which was supported by strong relationships between peak NO, $NO_{2}$, and HONO concentrations, high HONO/$NO_{2}$ ratio and a weak correlation between NO and HONO concentrations. Additionally, three combustion experiments during the whole measurement period were performed to investigate the effects of unvented and vented gas burning on the HONO, NO, and $NO_{2}$ concentrations and their decay. The decay rate of the HONO concentration was significantly less than the NO and $NO_{2}$ decay rates for all the experiments, indicating that the lifetimes of trace nitrogen species in indoor environment varied in the order approximately HONO>$NO_{2}$>NO.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.802-806
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• 2004

For the protection of the local air quality and the global atmosphere, the emissions of trace species including nitric oxides (NO and NO$_2$) from gas turbines are regulated by local governments and by the International Civil Aviation Organization. In-situ measurements of such species are needed not only for the development of advanced low-emission combustion concepts but also for providing emissions data required for the sound assessment of the effects of the emissions on environment. We have been developing a laser absorption system that has a capability of simultaneous determination of NO and NO$_2$concentrations in the exhaust jets from aero gas turbines. A diode laser operating near 1.8 micrometer is used for the detection of NO while a separated visible tunable diode laser operating near 676 nanometers is used for NO$_2$. The sensitivities at elevated temperature conditions were determined for simulated gas mixtures heated up to 500K in a heated cell of a straight 0.5 m optical path. Sensitivity limits estimated as were 30 ppmv-m and 3.7 ppmv-m for NO and NO$_2$, respectively, at a typical exhaust gas temperature of 800K. Experiments using the simulated exhaust flows have proven that $CO_2$ and $H_2O$ vapor - both major combustion products - do not show any interference in the NO or NO$_2$ measurements. The measurement system has been applied to the NO/NO$_2$ measurements in NO and NO$_2$ doped real combustion gas jets issuing from a rectangular nozzle having 0.4 m optical path. The lower detection limits of the system were considerably decreased by using a multipass optical cell. A pair of off-axis parabola mirrors successfully suppressed the beam steering in the combustion gas jets by centralizing the fluctuating beam in sensor area of the detectors.

• 한국대기환경학회지
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• 제21권1호
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• pp.1-14
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• 2005

In this study, a Long Path Differential Optical Absorption Spectroscopy system (K-JIST LP-DOAS) has been used to simultaneously measure atmospheric monoaromatic hydrocarbons and other trace compounds. The validity of the K-JIST LP-DOAS for measuring atmospheric monoaromatic hydrocarbons was tested during a field campaign between 12 February and 14 March 2003 at an urban site in Seoul, Korea through inter-comparative measurements against a collocated on-line Gas Chromatography (GC) system. The concentrations of benzene, toluene, p-xylene, and m-xylene were measured with the K-JIST LP-DOAS system in the UV region (239～302 nm) over a 740 m beam path. For the other trace compounds, a longer spectral range (299～362 nm) was used. In order to remove the interference of atmospheric abundant species (such as oxygen, sulfur dioxide and ozone), two oxygen optical density spectra obtained at two pathlengths, 697 and 1133m, and reference spectra of sulfur dioxide and ozone were incorporated in the fitting procedure. The mean concentrations measured by our LP-DOAS during the measurement period were 0.77 ($\pm$0.38) ppbv for benzene, 3.68 ($\pm$1.90) ppbv for toluene, 0.41 ($\pm$0.19) ppbv for p-xylene, 0.54 ($\pm$0.24) ppbv for m-xylene. The concentration data of benzene, toluene, p-xylene and m-xylene obtained by our LP-DOAS were found to be in relatively good correlations with those of the online GC system. Pearson's coefficients in the observed concentrations between LP-DOAS and on-line GC were 0.84 for benzene, 0.83 for toluene and 0.65 for m,p-xylene. This study suggests that the LP-DOAS system can be used to provide reliable information on both the mixing ratios and temporal distribution characteristics of monoaromatic hydrocarbons in the urban air.

• 한국대기환경학회지
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• 제18권2호
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• pp.127-137
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• 2002

Phenolic compounds in air are toxic even at their low concentrations. We had evaluated a total of five phenolic compounds (Phenol, o-Cresol, m-Cresol, 2-Nitrophenol and 4-Chloro-3-methylphenol) in artificial air using a combination of ATD/GC/MS. To compare the adsorption efficiency of these phenolic compounds, three adsorbents (Tenax TA, Carbotrap and Carbopack B) were tested. Tenax TA adsorbent was most effective of all the adsorbents used for the efficiency test. Five phenolic compounds were found to be very stable on adsorbent tubes for 4 days at room temperature. Detection limit of five phenolic compounds ranged from 0.05 to 0.08 ppb (when assumed to collect 10 L air). The calibration curve was linear over the range of 22∼ 164 ng. The reproducibility was less than 4%. Sampling of duplicate pairs (DPs) was made to demonstrate duplicate precision and sampling efficiency.

• 한국의류학회지
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• 제16권2호
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• pp.169-180
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• 1992

The purpose of this study is to investigate the effects of type of clothing microclimate and exercise condition on ventilation. The experimental system employed a trace gas technique of the previous research. Clothing microclimate volume measurement was based on the substitution water technique for inter-clothing air volume. The experimental variables were tested at four levels of clothing microclimate spacing, microclimate shape of the previous research and two levels of exercise conditions. 2, 4, 6 cm ease were added to B/2+4 of basic blouse pattern for the microclimate spacing variable. Each combination of three variables were tested in triplicate. Analysis of variance of experimental variables on vetilation, such as oxygen exchange rate, half time of first order model was conducted. Oxygen exchange rate and half time of first order model are affected by the shape of microclimate air and exercise condition.