• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.218-223
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• 2010

The zinc oxide thin film, which can be applied as the gas sensor of a semiconductor type, was grown on the silicon substrate by CFR(continuous flow reaction) method in this study. The growth property and the electrical property of the zinc oxide thin films synthesized by CFR method were also investigated. Zinc acetate solutions of 0.005~0.02 M were used as the precursor for the preparation of zinc oxide thin films. The size of ZnO particles consisted on the zinc oxide thin film increased not only with increasing concentration of precursor, but also the thickness of thin film increased. The growth rate of zinc oxide thin film by CFR method was proportionably depend on the concentration of precursor and the uniform ZnO thin film was prepared when zinc acetate of 0.01 M is used as the precursor. The charged currents on the zinc oxide thin films were obtained as its electrical property by I-V meter, and increased agree with increasing the thickness of zinc oxide thin film. Thus, it was concluded that the charged current on the zinc oxide thin film can be controlled with changing concentration of precursor solution in CFR method. The charged currents on the zinc oxide thin films also decreased when ZnO thin film is exposed under hydrogen sulfide of 500 ppmv at $300^{\circ}C$ for 5 min. From these results, it could be confirmed that the zinc oxide thin film prepared by CFR method can be used for the detection of sulfur compounds.

• Journal of Food Hygiene and Safety
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• v.32 no.6
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• pp.493-499
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• 2017

This study was conducted to monitor the current status of pesticide residues and sulfur dioxide in a total of 91 functional rice products from February to October 2016. Multi class pesticide multiresidue methods of 220 pesticides was performed by the GC/ECD, GC/NPD, GC/TOF/MS, LC/PDA, and LC/FLD. As a result of analysis, the pesticides were detected in 3 samples, representing a detection rate of 3.3%. The kind of pesticides was propiconazole and isoprothiolane used for germicide in agriculture or plant growth regulator purposes. The detected levels were 0.0340~0.0566 mg/kg, which were under the MRL (Maximum Residues Limits). The contents of sulfur dioxide in 91 samples by the Monier-Williams method were not detected. Risk assessment of pesticides evaluated using human health exposure with the ratio of EDI (Estimated daily intake) to ADI (Acceptable daily intake). %ADI (the ratios of EDI to ADI) were 0.24~1.25% with safety level.

• Analytical Science and Technology
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• v.18 no.1
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• pp.66-73
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• 2005

In this study, we investigated the gas chromatography (GC) and pulsed flame photometric detection (PFPD) system for the analysis of four major reduced S compounds including hydrogen sulfide ($H_2S$); methyl mercaptan ($CH_3SH$); dimethyl sulfide (DMS); and dimethyl disulfide (DMDS) contained in environmental samples. To analyze these compounds in high concentration range (above ppb level), we developed a high mode analytical setting with the loop-injection system. By contrast, we also established a low mode setting for the analysis of low concentration samples (ppt-level samples from ambient air) by the combination with thermal desorption unit (TDU). Comparative analysis of both settings revealed that relative detection properties of four S compounds are systematic enough. The results of high mode analysis indicated that the patterns were systematic among S compounds: $H_2S$ exhibited the lowest sensitivity, while DMDS showed the strongest one. The results were also compared in terms of sensitivity reductions for all compounds by dividing slope ratios between low and high mode system. Although low mode system exhibited significant reductions on the order of a few tens times, their detection characteristics were highly consistent as it was shown in the high mode setting. To learn more about absolute and relative relations between two different modes of S analysis, future studies may have to be directed to cover more complicated nature of GC/PFPD performance.

• Journal of Animal Environmental Science
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• v.19 no.2
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• pp.177-182
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• 2013

We studied the possibility to produce solid fuel using cattle manure and to apply TAO (Thermophilic Aerobic Oxidation) process of solid-liquid separation fraction. The physiochemical compositions of cattle manure solid fuel chip were analyzed as water 0.12%, low calorific value 3,510 kcal/kg, ashes 11.9%, chlorine 0.82%, sulfur dust 0.5%, mercury non-detection, cadmium 1.0 mg/kg, lead 2 mg/kg, arsenic non-detection. In treating cattle manure with TAO reactor the internal temperature of the reactor was increasing higher and $50^{\circ}C$ and over was maintained after 20 hours on. The physiochemical compositions of liquids increased from pH 7.3 to pH 9.18 and EC decreased from 4.6 to 3.48 mS/cm in treating process of cattle manure with TAO reactor. COD and SCOD decreased from 16,800 to 10,400 mg/L, from 4,600 to 2,040 mg/L respectively, which showed about 38% and 56% of remove efficiency respectively.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.6
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• pp.679-687
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• 2003

In this study, we investigated the analytical techniques to quantify the ambient concentration of hydrogen sulfide (H$_2$S) in air at ppt concentration level. For this purpose, an on-line GC analytical system equipped with both pulsed-flame photometric detector (PFPD) and thermal desorption unit (TDU) was investigated by collecting ambient air samples. The results of our study generally indicated that calibration conditions of GC system is highly sensitive to affect the accuracy of the analytical technique. Most importantly. we found that the use of different matrices in the the preparation stage of working standards was sensitive to control the overall performance of this technique. The calibration of our analytical system was tested by the two types of working standard (prepared by mixing either with high purity $N_2$ or with the ambient air). According to this test, the latter represented more efficiently the detecting conditions of actual air samples. The peak occurrence patterns of both air samples and standards (prepared by mixing with ambient air) were altered in a similar manner as the function of the loaded volume; however, it was not the case for the $N_2$-mixed standards. Results of our study suggest that detection of H$_2$S is highly different from other sulfides and that its quantification requires minimiaing interfering effects of non -pure substance (like water vapor) and (either sorptive or destructive) loss effects.

• Preventive Nutrition and Food Science
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• v.14 no.1
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• pp.76-85
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• 2009

This study determined the effect of refrigerated and thermal storage on the volatile profile of commercial aseptic soymilk. Volatile components in commercial aseptic soymilk stored either under refrigerated ($4^{\circ}C$) or thermal ($55^{\circ}C$) conditions for 30 days were periodically analyzed by combined solvent-assisted flavor evaporation-gas chromatography-mass spectrometry (SAFE-GC-MS). The concentrations of most of the volatile components, including aldehydes, ketones, alcohols, acids, nitrogen- and sulfur-containing compounds, alkylfurans, furan derivatives and phenolic compounds, were affected to a greater extent by thermal storage compared with refrigerated storage. Profound increases in some volatile compounds with low odor detection thresholds, such as hexanal, octanal, (E)-2-octenal, (E,E)-2,4-decadienal, 1-octen-3-ol, 3-ethyl-2,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, 2-pentylfuran, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, dimethyl trisulfide, guaiacol, 4-vinylguaiacol and 4-vinylphenol, were observed in thermal stored soymilk. The volatile profile changes caused by thermal storage may influence the aroma quality of thermal-stored aseptic soymilk.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.237-240
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• 2004

Sulfur Hexafluoride, SF6 is widely used for leak detection and as a gaseous dielectric in transformers, condensers and circuit breakers. SF6 gas is also effective as a cleanser in the semiconductor industry. This paper presents a numerical study of the sealing force of disk type seal in SF6 gas safety valve. The sealing force on the disk seal is analyzed by the FEM method based on the Taguch's experimental design technique. Disk seals in SF6 gas safety valve are designed with 9 design models based on 3 different contact length, compressive ratio and gas pressure. The calculated results of Cauchy stress and strain showed that the sealing characteristics of Teflon PTFE is more effective compared to that of FKM(Viton), which is related to the stiffness of the materials. And also, the contact length of the disk seal is important design parameter for sealing the SF6 gas leakage in the safety valve.

• Analytical Science and Technology
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• v.7 no.3
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• pp.349-359
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• 1994

A gas chromatographic method for analyzing the gas odorants concentration in natural gas was studied. Eight odorants involving TBM and THT were completely separated by using OV-10 column. The optimization of several interrelated key parameters affecting the response of FPD such as hydrogen flow rate, air flow rate and detector temperature were accomplished. A permeation device was used to obtain calibration curves of TBM and THT. This analytical method has applied to measure TBM and THT used as a natural gas odorant blend in natural gas pipeline. In order to elucidate the relationship between odor level and odorant level feasibility test of fragrance meter was demonstrated.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.6
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• pp.441-446
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• 2006

Volatile flavor compounds in meat of the blue crab Portunus trituberculatus were compared using vacuum simultaneous steam distillation-solvent extraction (V-SDE) and solid phase microextraction (SPME)/ gas chromatography (GC)/ mass selective detection (MSD) methods. A total of 100 volatile flavor compounds were identified by both methods: 77 by V-SDE and 59 by SPME. These compounds were composed of 17 aldehydes, 12 ketones, 19 alcohols, 5 esters, 4 sulfur-containing compounds, 6 nitrogen-containing compounds, 23 aromatic compounds, 6 hydrocarbons, 2 terpenes, and 6 miscellaneous compounds. Although more compounds were detected using V-SDE than using SPME, the levels of all groups detected, except esters, were higher using SPME than using V-SDE. In addition to trimethylamine, aldehydes, and aromatic compounds, the S- and N-containing compounds with low thresholds are thought to have positive roles for flavors in the meat of the blue crab.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.1
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• pp.91-99
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• 1996

Ozone, sulfur dioxide, and nitrogen oxides were measured at Kosan, Cheju Island, Korea during the period of March 11 .sim. April 19, 1994. During the measurement period, the average SO$_{2}$ and NOx concentrations were about 0.97 ppb and 3.5 ppb, respectively. Average NO concentration was below the detection limit and thus the effect of NO during the period was negligible. The concentrations of SO$_{2}$ and Nox were lower than those at other urban area in Korea but higher than other remote areas in the world. Average $O_{3}$ concentration for the period was about 55 ppb, slightly higher than or comparable to those at remote marine areas in the world. Detailed analyses of trend of gaseous species concentrations show that the effects of local NO emission sources for NOx concentration were significant during the period, while those of local SO$_{2}$ emission sources were not high. Backward trajectory analysis results show that when SO$_{2}$ or $O_{3}$ concentration was higher than the average concentrations, the air parcels were transported from China.