• Journal of the Korean Society of Safety
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• v.36 no.1
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• pp.1-8
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• 2021

To simulate a process model in the field of chemical engineering, it is very important to identify the physical properties of novel materials as well as existing materials. However, it is difficult to measure the physical properties throughout a set of experiments due to the potential risk and cost. To address this, this study aims to develop a property prediction model based on the group contribution method for aromatic chemical compounds including benzene rings. The benzene rings of aromatic materials have a significant impact on their physical properties. To establish the prediction model, 42 important functional groups that determine the physical properties are considered, and the total numbers of functional groups on 147 aromatic chemical compounds are counted to prepare a dataset. Support vector regression is employed to prepare a prediction model to handle sparse and high-dimensional data. To verify the efficacy of this study, the results of this study are compared with those of previous studies. Despite the different datasets in the previous studies, the comparison indicated the enhanced performance in this study. Moreover, there are few reports on predicting the physical properties of aromatic compounds. This study can provide an effective method to estimate the physical properties of unknown chemical compounds and contribute toward reducing the experimental efforts for measuring physical properties.

• Korean Journal of Weed Science
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• v.17 no.4
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• pp.375-381
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• 1997

When the rice straw mulched, the inhibition of weed growth was observed in the paddy field. If we use these allelopathic effect of decreased weed establishment, we can save labor, and protect environment. Aqueous extract of rice straw were bioassayed using water foxtail seeds to investigate chair effects on the germination and the growth, and to identify allelopathic compounds. The major results obtained were summarized as follows : Aqueous extract was fractioned by solvent, among various fractions, II-3, II-4 fractions inhibited the coleoptile and the radical of water foxtail, by 100%, respectively. There were fumaric acid and 4 unknown organic acids. Seven organic acids including fumaric acid inhibited the growth and germination of water foxtail in $10^{-2}$M solution. One of the most effective allelopathic compounds in rice straw was identified the unknown organic acid, as molecular weight 253, by GC/MS.

• Journal of Nutrition and Health
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• v.4 no.1
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• pp.63-67
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• 1971

The nitrogen content and free amino acids were determined from the saute of mong bean paste which is one of the important protein sources on Korean diet. During the saute' process of mong-bean paste, valine, r-aminobutyrate, glutamine, arginine, methionine, and unknown acids were lost, but, proline, lysine, homoserine, and tyrosine were detected.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.2
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• pp.113-126
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• 2002

This study was carried out to evaluate the temporal (daily, weekly, and seasonal) variations of volatile organic compounds (VOCs) concentrations at a road-side site in a heavy-traffic central area of Metropolitan Taegu. Ambient air sampling was undertaken continuously for 14 consecutive days in each of four seasons from the spring of 1999 to the winter of 2000. The VOC samples were collected using adsorbent tubes, and were determined by thermal desorption coupled with GC/MS analysis. A total of 10 aromatic VOCs of environmental concern were determined, including benzene, toluene, ethylbenzene, m＋p-xylenes, styrene, o-xylene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, and naphthalene. Among 10 target VOCs, the most abundant compounds appeared to be toluene (1.5 ∼ 102 ppb) and xylenes (0.1 ∼ 114 ppb), while benzene levels were in the range of 0.3 ∼6 ppb. It was found that the general trends of VOC levels were significantly dependent on traffic conditions at the sampling site since VOC concentrations were at their maximum during rush hours (AM 7∼9 and PM 7 ∼9). However, some VOCs such as toluene, xylenes, and ethylbenzene were likely to be affected by a number of unknown sources other than vehicle exhaust, being attributed to the use of paints, and/or the evaporation of solvents used nearby the sampling site. In some instances, extremely high concentrations were found for these compounds, which can not be explained solely by the impact of vehicle exhaust. The results of this study may be useful for estimating the relative importance of different emission sources in large urban areas. Finally, it was suggested that the median value might be more desirable than the arithmetic mean as a representative value for the VOC data group, since the cumulative probability distribution (n=658) does not follow the normal distribution pattern.

• Analytical Science and Technology
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• v.21 no.2
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• pp.65-83
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• 2008

It is noted that illegal hazardous foods containing unauthorized drugs or synthetic drung analogues are increasing. Especially, reported are unknown compounds that have the modified chemical structures of the anti-impotence drugs such as sildenafil, vardenafil, and tatalafil. In addition, it is very reserved, since illegal synthetic compounds having similar chemical structures modified from anti-impotence drug to avoid the government inspection are not proved their safety at all. This review in ulation to food safety, lists the illegal compounds added to foods and describes about the analytical methods to chanacterize 16 anti-impotence drug analogues such as homosildenafil, hongdenafil, pseudovardenafil, aminotadalafil, hydroxyhomosildenafil, hydroxyhongdenafil, dimethylsildenafil, xanthoanthrafil, hydroxyvardenafil, norneosildenafil, demethylhongdenafil, piperidinohongdenafil, carbodenafil, thiosildenafil, dimethylthiosildenafil, and acetylvardenafil.

• Analytical Science and Technology
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• v.28 no.4
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• pp.278-287
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• 2015

Phosphodiesterase type 5 inhibitors (PDE-5 inhibitors) are used in the treatment of erectile dysfunction. In recent years, a number of reports have been conducted on dietary supplements contaminated with PDE-5 analogues. In this study, 58 analogues of PDE-5 inhibitors were sorted into five groups: tadalafil, sildenafil, hongdenafil, vardenafil, and other analogues. These analogues were then evaluated using a liquid chromatography-quadrupole-time of flight mass spectrometry (LC-QTOF-MS) electrospray ionization mass method. Each compound has a unique fragmentation ion, which can be easily analyzed qualitatively. The fragmentation pathways of the analogues were elucidated based on the QTOF-MS and MS/MS data. Common ions were confirmed for each group by analyzing the structural characteristics and fragmentation pathways. Specifically, common ions were observed at m/z 169.08 and 135.04 (tadalafil analogues), m/z 311.15 and 283.12 (sildenafil analogues and hongdenafil analogues), and m/z 312.16 and 151.09 (vardenafil analogues). The advantage of this method is that the structure of unknown components can be determined by interpreting the product ions. Hence, the developed method can be used for the identification of unknown compounds. Fragmentation pathways may also aid in the detection and identification of PDE-5 inhibitor analogues.

• Journal of Korean Society on Water Environment
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• v.31 no.1
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• pp.29-34
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• 2015

The aim of this study is to understand the limitation of organic pollutant indexes ($BOD_5$, $COD_{Mn}$, $COD_{Cr}$) and estimate to set the TOC standard by comparing oxidation rates of $BOD_5$, $COD_{Mn}$, $COD_{Cr}$ and TOC based on the 487 organic compounds and 11 effluents from industrial wastewater containing various and unknown organic compounds. The range of ratio of theoretical oxygen demand (ThOD) to theoretical organic carbon (TOCt) was 0.00~5.33 and average ratio of classes of organic compounds was 2.68~3.70. According to classes of organic compounds, the average ratio of $O_2/C$ was 1.2 (range : 1.02~1.39). The order of oxidation rate for 15 organic compounds was TOC (90.7%) > $COD_{Cr}$ (88.8%) > $BOD_5$ (54.4%) > $COD_{Mn}$ (30.8%) indicating the lower oxidation rate of $BOD_5$ and COD compared with TOC. The ranking for average oxidation rate was $COD_{Cr}$ > $COD_{Mn}$ > $BOD_5$ indicating that $BOD_5$, $COD_{Mn}$ could be underestimated comparing with ThOD of organic compounds in case of industrial wastewater containing high concentration of refractory organic compounds. Most of the relationships between organic pollutant indexes and TOC were higher than 0.9. The ratio of TOC to organic compound indexes decreased in the order : $COD_{Cr}$ (3.4) > $COD_{Mn}$ > (1.9) > $BOD_5$ (0.7).

• Journal of Korean Society of Forest Science
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• v.100 no.3
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• pp.367-373
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• 2011

The demand for Japanese larch (Larix kaempferi) seeds has increased in Korea but their supply has been limited due to sporadic natural seed production. To enhance seed production, stem girdling was applied to 42-yearold Japanese larches, resulting in remarkable enhancement of strobilus production in terms of the rate of strobilusbearing tree and the number of strobilus per tree. Metabolic alterations in the girdled and the control trees were interrogated through GC/MS analysis. In the girdled tree, the contents of 14 individual metabolites including polar and non-polar compounds were significantly increased compared to the control. In the cambium and phloem tissues of girdled trees, the contents of pimaric acid, phosphoric acid, sucrose, and two different unknown compounds were enhanced, while the levels of malic acid, inositol, two different disaccharide, 11-trans-Octadecenoic acid and 4 different unknown compounds were decreased compared to the control. The girdled trees showed to be contained significantly higher amount of total nitrogen in the cambium and phloem tissues than that of control trees. Although the role of individual metabolites on enhanced strobilus production remains unclear, the approach presented in this study might provide useful information in elucidating metabolic network modulation induced by girdling and will be further applied for enhanced strobilus production in Japanese larch trees.

• Analytical Science and Technology
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• v.9 no.1
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• pp.1-12
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• 1996

The thermally labile compounds with hydroxyl group generate the [${MNH_4}^+$] ion, [$MH^+$] and [$MH^+-OH$] ion by ion-molecule reaction in LC/TSP/MS. But these ions create the trouble in the estimation of molecular weight of an unknown compound because the margin of [${MNH_4}^+$] ion and [$MH^+$] ion is same to that of [$MH^+$] ion and [$MH^+-OH$] ion. If it is compensated for the results by using of the $CF_3COOD+NH_4OH$ LC eluent, the molecular weight of analyte will be able to be confirmed. And this study was tried to recognize whether the fragment ions of thermally labile compound are generated by electron impact or by thermal degradation in ion source.

• Journal of Applied Biological Chemistry
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• v.44 no.1
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• pp.12-15
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• 2001

The antioxidative compounds and antioxidant contents of ginger (Zingiber officinale) rhizomes were determined. Substances reextracted using ethyl acetate from crude methanol extract of fresh ginger rhizome were separated through thin layer chromatography. Ten phenolic antioxidative bands were visualized through color reactions using ferric chloride-potassium ferricyanide and 1,1-diphenyl-2-picrylbydrazyl (DPPH). The antioxidative compounds were purified through preparative TLC and high performance liquid chromatography (HPLC), among which, five antioxidants were identified as 4-, 6-, 8-. and 10-gingerols and 6-shogaol on the basis of their molecular weights determined through LC-MS. As shown in experiments using DPPH free radicals, 6-Gingerol and PT4-HP8 (unknown) were revealed to be more efficient than BHT (butylated hydroxy toluene). Contents of gingerols were determined through reverse phase HPLC. Total gingerol contents (sum of 6-,8-, and 10-gingerols) in rhizomes of different ginger varieties varied significantly. The HG55 (collected at Wanju district in Korea) and the HG52 (imported from Brazil) showed the highest gingerol contents.