• Analytical Science and Technology
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• v.26 no.5
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• pp.326-332
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• 2013

Geosmin and 2-methylisoborneol (2-MIB) are volatile organic compounds responsible for the majority of unpleasant taste and odor events in drinking water. Geosmin and 2-MIB are byproducts of blue-green algae (cyanobacteria) with musty and earthy odors. These compounds have odor threshold concentration at ng/L levels. It is needed to develop a sensitive method for determination of geosmin and 2-MIB to control the quality of drinking water. In this study, geosmin and 2-MIB in water samples were determined by gas chromatography-mass spectrometry (GC-MS) with headspace-solid phase microextraction (HS-SMPE). The detection limits of this method were 1.072 ng/L and 1.021 ng/L for geosmin and 2-MIB, respectively. Good accuracy and precision was also obtained by this method. Concentrations of the two compounds were measured in raw waters from Nakdong River in the cyanobacterial blooming season. Water bloom formed by cyanobacteria has been occurred currently in Nakdong River. It is needed to investigate the concentrations of geosmin and 2-MIB to control the quality of drinking water from Nakdong River. Both geosmin and 2-MIB were detected in raw waters from Nakdong River at concentrations ranging from 4 to 24 ng/L and 6 to 16 ng/L, respectively.

• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.329-334
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• 2004

The electronic nose (E-nose) recently finds its applications in medical diagnosis, specifically on detection of diabetes, pulmonary or gastrointestinal problem, or infections by examining odors in the breath or tissues with its odor characterizing ability. The odor recognition performance of E-nose can be improved by manipulating the sensor array responses of vapors in time-profile forms. The different chemical interactions between the sensor materials and the volatile organic compounds (VOC's) leave unique marks in the signal profiles giving more information than collection of the conventional piecemal features, i.e., maximum sensitivity, signal slopes, rising time. In this study, to use them in vapor recognition task conveniently, a novel time-profile method was proposed, which is adopted from digital image pattern matching. The degrees of matching between 8 different vapors were evaluated by using the proposed method. The test vapors are measured by the silicon-based gas sensor array with 16 CB-polymer composites installed in membrane structure. The results by the proposed method showed clear discrimination of vapor species than by the conventional method.

• Journal of Radiation Protection and Research
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• v.20 no.2
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• pp.79-83
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• 1995

A number of investigators have reported formation of radiolytic ultrafine particles produced by the interaction of ionizing radiation with atmospheric trace gases. Previous studies have suggested that a very high localized concentration of the hydroxyl radical produced by the radiolysis of water can react with atmospheric trace gases such as $SO_2$ and produce lower vapor pressure compounds that can subsequently nucleate. To determine the trace gas and water vapor concentration dependence of the active, positively charged, first decayt product of radon (Po-218), a well-controlled radon chamber was used in this research. The mobility spectrum of the decay products in the range of $0.07-5.0cm^2/V\;sec$ from the radon chamber was measured using alpha track detector installed inside a specially-designed electrostatic spectrometer. Measurements were taken for different concentrations (0.5ppm to 5ppm) of $SO_2$ in Purified, Compressed air. A kinetics Study following the clustering of $SO_2$ around the $PoO_x^+$ ion in an excess of $SO_2$ for interpretation of the reaction processes was performed.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.5
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• pp.262-268
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• 2015

This study established an analytical method to simultaneously determine six organophosphorous pesticides [methyldemetone-S, diazinon, fenitrothion, parathion, phentoate, and O-ethyl O-(4-nitrophenyl) phenylphosphonothioate (EPN)] and carbaryl in water using a gas chromatography/mass spectrometry (GC/MS) system coupled with on-line micro extraction by packed sorbent (MEPS) and programmed temperature vaporizer (PTV) injector. Polystyrene divinylbenzene (PDVB) was used as a sorbent of MEPS. The effects of elution solvents, pH, elution volume and draw-eject cycles of samples on sample pretreatment process were investigated. Also, quality assurance and quality control (QA/QC) and the recovery of the pesticides in environmental samples were evaluated. The elution was performed using $30{\mu}L$ of a mixed solvent (acetone : dichloromethane = 80 : 20 (v/v)). Sample pretreatment processes were optimized with seven cycles of draw-eject of sample (1 mL) spiking an internal standard and sulfuric acid. At lower pH, the analytical sensitivity of diazinon decreased, but that of carbaryl increased. The method detection limit and the limit of quantification for this method were 0.02~0.18 and $0.08{\sim}0.59{\mu}g/L$, respectively. The method precision and accuracy were 1.5~11.5% and 83.3~129.8%, respectively, at concentrations of $0.5{\sim}5.0{\mu}g/L$. The recovery rates for all the pesticides except carbaryl in various environmental samples ranged 75.7~129.3%. The recovery rate of carbaryl in effluent sample was over 200% whereas carbaryl in drinking water, groundwater, and river water were in the acceptable range.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.83.1-83.1
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• 2011

We report multi-epoch, simultaneous 22 GHz water and 44 GHz Class I methanol maser line survey towards 180 intermediate-mass young stellar objects, including 14 Class 0, 19 Class I objects, and 147 Herbig Ae/Be stars. We detected $H_2O$ and $CH_3OH$ maser emission towards 16 (9%) and 10 (6%) sources with one new $H_2O$ and six new $CH_3OH$ maser sources. The detection rates of both masers rapidly decrease as the central (proto)stars evolve, which is contrary to the trends in high-mass star-forming regions. This suggests that the excitations of the two masers are closely related to the evolutionary stage of the central (proto)stars and the circumstellar environments. $H_2O$ maser velocities deviate on average 9 km s-1 from the ambient gas velocities whereas $CH_3OH$ maser velocities well match with. For both maser emissions, large velocity difference (${\mid}v_{H2O}-v_{sys}{\mid}\;>\; 10kms^{-1}\; and\;{\mid}v_{CH3OH}-v_{sys}{\mid}\;>\;1kms^{-1}$) is mostly confined to Class 0 objects. The formation and disappearance of $H_2O$ maser lines are frequent and the integrated intensities of them change up to two orders of magnitude. In contrast, $CH_3OH$ maser lines usually show no significant change in the intensity, shape, and velocity. This consistent with the previous suggestion that $H_2O$ maser emission originates from the base of an outflow while 44 GHz Class I $CH_3OH$ maser emission arises from the interaction region of the outflow with the ambient gas. The isotropic maser luminosities are well correlated with the bolometric luminosities of the central the objects. The fitted relations are $L_{H2O}=1.71{\ast}10^{-9}(L_{bol})^{0.97}$ and $L_{CH3OH}=1.71{\ast}10^{-10}(L_{bol})^{1.22}$.

• Journal of the Korean Institute of Gas
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• v.16 no.3
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• pp.22-28
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• 2012

For a methanol separation column of the BPA (Bisphenol A) plant, HAZOP (hazard and operability) assessment was performed and damage ranges were predicted from the accident scenarios for the fire and the explosion. As a result, the damage range of the jet fire was 20 m in the case of rupture of the discharge pipe (50 mm diameter) of safety valve, and that of the flash fire was 267 m in the case of catastrophic rupture. Also, the damage ranges of the unconfined vapor cloud explosion (UVCE) for the rupture of the discharge pipe and for the catastrophic rupture were 22 m and 542 m, respectively. For the worst case of release scenarios, safety measures were suggested as follows: the pressure instruments, which can detect abnormal rise of the internal pressure in the methanol separation column, should be installed by the 2 out of 3 voting method in the top section of the column. Through the detection, the instruments should simultaneously shut down the control and the emergency shut-off valves.

• Journal of Sensor Science and Technology
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• v.7 no.4
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• pp.254-262
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• 1998

Multilayer Langmuir-Blodgett (LB) films coated on quartz crystal microbalance (QCM) of octa-substituted metallophhtalocyanines ($MPc(OEH)_8$, M = Cu, Co, and Sn) and dihydrogen phthalocyanines ($H_2Pc(OEH)_8$) were used to quantify $NO_2$ concentrations. They were exposed to various concentrations of $NO_2$ in dry $N_2$. Among the four phthalocyanines we tested, the metal-free $H_2Pc(OEH)_8$ was observed to be most sensitive to $NO_2$. However, its LB film showed a partially irreversible behavior, that is part of the frequency change due to $NO_2$ adsorption could not be recovered even after purging with pure $N_2$ gas for an extended period. Examining the spectra of NMR and FTIR revealed fact that the irreversible portion of frequency change was due to ether groups in the linkage between side chains and the Pc unit. In order to remove the effect of such initial deactivation, on $NO_2$ quantification experiment, a freshly fabricated LB film was treated at a high concentration of $NO_2$ so that the ether sites were saturated. A pretreated LB film showed a reproducible performance for repeated uses. The $CuPc(OEH)_8$ LB film showed a satisfactory sensing performance down to as low as 4 ppm. For the $H_2Pc(OEH)_8$ LB film, the lower detection limit was found to be 35ppb of $NO_2$. In order to make the experimental condition more realistic, the carrier gas, dry nitrogen, was replaced by air. It was observed that the presence of oxygen, a weak electron acceptor, reduced the sensitivity and thus increased the sensing limit to hundreds of ppb. Results of experiments with moisture added showed that the interference of moisture was quite severe.

• Environmental Analysis Health and Toxicology
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• v.17 no.3
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• pp.197-205
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• 2002

Volatile organic compounds (VOCs) are an important public health problem throughout the world. Many important questions remain to be addressed in assessing exposure to these compounds. Because they are ubiquitous and highly volatile, special techniques must be applied in the analytical determination of VOCs. Personal exposure measurements are needed to evaluate the relationship between microenvironmental concentrations and actual exposures. It is also important to investigate exposure frequency, duration, and intensity, as well as personal exposure characteristics. In addition to air monitoring, biological monitoring may contribute significantly to risk assessment by allowing estimation of absorbed doses, rather than just the external exposure concentrations, which are evaluated by environmental and personal monitoring. This study was conducted to establish the analytic procedure of VOCs in air, blood, urine and exhaled breath and to evaluate the relationships among these environmental media. The subjects of this study were selected because they are occupationally exposed to high levels of VOCs. Environmental, personal, blood, urine and exhalation samples were collected. Purge ＆ trap, thermal desorber, gas chromatography and mass selective detector were used to analyze the collected samples. Analytical procedures were validated with the“break through test”, 'quot;recovery test for storage and transportation”,“method detection limit test”and“inter-laboratory QA/QC study”. Assessment of halogenated compounds indicted that they were significantly correlated to each other (p value < 0.01). In a similar manner, aromatic compounds were also correlated, except in urine sample. Linear regression was used to evaluate the relationships between personal exposures and environmental concentrations. These relationships for aromatic and halogenated are as follows: Halogen $s_{personal}$ = 3.875+0.068Halogen $s_{environmet}$, ($R^2$= .930) Aromatic $s_{personal}$ = 34217.757-31.266Aromatic $s_{environmet}$, ($R^2$= .821) Multiple regression was used to evaluate the relationship between exposures and various exposure deter-minants including, gender, duration of employment, and smoking history. The results of the regression model-ins for halogens in blood and aromatics in urine are as follows: Halogen $s_{blood}$ = 8.181+0.246Halogen $s_{personal}$+3.975Gender ($R^2$= .925), Aromatic $s_{urine}$ = 249.565+0.135Aromatic $s_{personal}$ -5.651 D.S ($R^2$ = .735), In conclusion, we have established analytic procedures for VOC measurement in biological and environmental samples and have presented data demonstrating relationships between VOCs levels in biological media and environmental samples. Abbreviation GC/MS, Gas Chromatography/Mass Spectrometer; VOCs, Volatile Organic Compounds; OVM, Organic Vapor Monitor; TO, Toxic Organicsapor Monitor; TO, Toxic Organics.

• Korean Journal of Environmental Agriculture
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• v.16 no.4
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• pp.333-340
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• 1997

An analytical method was developed to determine residues of haloxyfop-R and its methyl ester in soils and soybeans using gas-liquid chromatography (GLC) with electron capture detector (ECD). Soil or soybean sample was acidified and extracted with acetone. The extract was then subjected to ion-associated partition to individually separate haloxyfop-R and the neutral methyl ester. One phase containing haloxyfop-R was methylated with $BF_3$/methanol, partitioned to n-hexane and analyzed by GLC/ECD. The other phase containing the methyl ester was further purified by Florisil column chromatography prior to GLC determination. No cross contamination was found between two phases containing each of the acid and methyl ester, thus two compounds can be separately determined as the identical haloxyfop-R-methyl. Overall recoveries of haloxyfop-R from fortified samples averaged 88.2${\pm}$3.9% (n=12) and 88.3${\pm}$4.0% (n=6) for soils and soybeans respectively, and those of haloxyfop-R-methyl showed mean values of 89.2${\pm}$4.0% (n=12) and 85.6${\pm}$5.6% (n=6). Detection limits of both haloxyfop-R and its methyl esterwere 0.005㎎/㎏ and 0.01㎎/㎏ for soil and soybean samples respectively.

• Analytical Science and Technology
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• v.16 no.1
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• pp.70-77
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• 2003

The optimum conditions for the residue analysis of hydroxyanilide fungicide fenhexamid on cucumber, strawberry and grape were investigated by gas chromatography equipped with electron capture detector (GC-ECD) and the residual amount was determined by sprayed days before harvest. Each samples were extracted with acetone, filtered and concentrated to 50 mL. The concentrated extracts were transferred to dichloromethane and then thoroughly concentrated. The concentrated phase was loaded on the filtration column stuffed with silica gel and purified with acetone:hexane (5:95, 15:85, v/v) mixed solvent. The regression equation and linearity of the standard calibration curves between 0.05~2.00 ng were as follows : cucumber; Y=312.40X+10.26, $R^2=0.9996$, strawberry; Y=313.33X+5.54, $R^2=0.9998$, grape; Y=253.27X-2.23, $R^2=0.9994$. From the standard additional experiments with 0.10 mg/L and 0.40 mg/L, the average recoveries of cucumber, strawberry and grape were 94.8%, 88.1% and 93.7%, respectively and the detection limits were all the same as 0.01 mg/L. Residual amounts in crops were ranged from 0.01 to 0.58 mg/L.