• Bulletin of the Korean Chemical Society
• /
• v.33 no.5
• /
• pp.1693-1698
• /
• 2012

A headspace gas chromatographic mass spectrometric (GC-MS) assay method was developed for the simultaneous determination of methyl tertiary butyl ether (MTBE), $tert$-butyl alcohol (TBA) and benzene, toluene, ethyl benzene and xylene (BTEX) in soil contaminated with gasoline. 2 g of soil sample were placed in a 10 mL headspace vial filled with 5 mL of phosphoric acid solution (pH 3) saturated with NaCl, and the solution was spiked with fluorobenzene as an internal standard and sealed with a cap. The vial was heated in a heating block for 40 min at $80^{\circ}C$. The detection limits of the assay were 0.08-0.12 ${\mu}g$/kg for the analytes. For five independent determinations at 10 and 50 ${\mu}g$/kg, the relative standard deviations were less than 10%. The method was used to analyze fifty six soil samples collected from various regions contaminated with gasoline in Korea. The developed method may be valuable for the monitoring of the analytes in soil.

• Microbiology and Biotechnology Letters
• /
• v.36 no.4
• /
• pp.336-342
• /
• 2008

The effect of methyl tert-butyl ether (MTBE) and its metabolites like tert-butyl alcohol (TBA), and formaldehyde (FA) on microbial activity and diversity in tidal mud flat was studied. MTBE, TBA, and FA with different concentrations were added into microcosms containing tidal mud samples, and placed at room temperature for 30 days. Then the physico-chemical properties such as pH, moisture contents and organic matter contents in the microcosms were measured. In addition, the total viable cell number and dehydrogenase activity were measured. Bacterial communities in the microcosms were monitored using a 16S rRNA-PCR-DGGE (Denaturing gradient gel electrophoresis) fingerprinting method. As a result, the exposure concentrations of MTBE and its metabolites showed no correlation with the physico-chemical factors (P>0.05). Dehydrogenase activity and total viable cell number were decreased with increasing MTBE, TBA and FA concentrations (P<0.05). The toxic effect was higher the following order: FA > MTBE > TBA. Dominant species in the microcosms contaminated with MTBE and its metabolites were Sphingobacteria, Flavobacteria, delta-proteobacteria, gamma-proteobacteria. The diversity of bacterial community was not significantly influenced by MTBE and its metabolites.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.51 no.6
• /
• pp.544-553
• /
• 2006

In order to assess antioxidant capacity in relation to seed traits of rice (Oryza sativa L.), ninety-six varieties were examined for antioxidative activity of brown rice grain using superoxide dismutase (SOD), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and thiobarbituric acid (TBA) assays. Overall, average total activities measured by the three methods were of very wide range between 64% and 13%. Significant differences were noted depending on the variety and evaluation method. Rice varieties with foreign origin, middle maturity, colored hulls, and colorless awn exhibited statistically significant higher total activity. As for the measurements, total activity was significantly correlated with SOD (r=0.29***), DPPH (r=0.80***) and TBA (r=0.76***). Between the three activities, SOD was not positively correlated with DPPH (r=0.15*), while TBA was significantly correlated with DPPH value (r=0.51***). DPPH (55.20%) and TBA (50.36%) were significantly higher in foreign rice, while SOD activity (44.29%) was significantly higher in domestic rice. However, an average total activity was significantly higher in foreign rice (47.31%) than in domestic rice (35.92%). SOD, DPPH and TBA activities of middle maturity in maturity time were the highest total activity (44.96%) and significantly differed from the other two groups. Total activity was significantly higher in rice with a colorless awn (42.18%) than with a colored awn (35.87%).

• Korean Journal of Clinical Laboratory Science
• /
• v.39 no.3
• /
• pp.196-200
• /
• 2007

In clinical practice, homocysteine has gained popularity because its elevated values are strongly associated with an increased risk of cardiovascular disease. More recently, a new enzymatic colorimetric assay for homocysteine in biological sample, suitable for automated clinical analyzers, has been proposed. To evaluate one of these enzymatic methods and compare the results obtained with this method with those of an immunoenzymatic method, thirty-two samples were analyzed for total homocysteine by HiSens$^{(R)}$ homocysteine reagent on the automated chemistry analyzers TBA 200FR and compared to the widely used immunoenzymatic method ADVIA Centaur. In TBA 200FR, the within-run CVs of two control materials were 3.23% and 0.92%, respectively; the between run CVs were 4.58% and 2.55%, respectively. And in ADVIA 1650, the within-run CVs were 6.81% and 0.99%, respectively; the between run CVs were 9.0% and 3.9%, respectively. The recovery for homocysteine was 100% ($60.8{\mu}mol/L$), 99.1% ($48.64{\mu}mol/L$), 96.3% ($36.48{\mu}mol/L$), 96.1% ($24.32{\mu}mol/L$), and 92.1% ($12.16{\mu}mol/L$). The regression equation of TBA 200FR vs. ADVIA Centaur was y=0.9095x-2.5086 (r=0.9632). And the regression equation for the ADVIA 1650 chemistry vs. Immulite 2000 was y=0.8418x + 0.3207 (r=0.9625). In conclusion, this enzymatic method using automated chemistry analyzer for homocysteine assay shows acceptable analytical performance. I suggest that this assay will be suitable for routine analysis.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.12
• /
• pp.4286-4290
• /
• 2011

A novel catalytic synthesis of biscoumarins from 4-hydroxycoumarin and aromatic aldehydes has been developed. The reaction occurs in ethanol in the presence of tetrabutylammonium hexatungstate $[TBA]_2[W_6O_{19}]$ as catalyst to give the corresponding products in high yields. This new approach has short reaction times, clean reaction profiles, and simple experimental and workup procedures. Moreover, the catalyst can be easily recovered by filtration and used at least three times with only slight reduction in its catalytic activity.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.11
• /
• pp.3597-3600
• /
• 2012

Thrombin binding aptamter (TBA-15) is a 15-mer guanine-rich oligonucleotide. This DNA apamer specifically binds to the thrombin protein involved in blood coagulation. Using extensive umbrella sampling molecular dynamics simulation method at all atom level, we investigated the potential of mean force (PMF) upon pulling the DNA aptamer from the binding mode of aptamer/thrombin complex. From this calculation, the free energy cost for a full dissociation of this aptamer/protein complex is 17 kcal/mol, indicating a substantial binding affinity of TBA-15. Interestingly, this PMF reveals noticeable plateau regions along the pulling coordinate. Possible structural changes of this complex in the plateau were investigated in details.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.3
• /
• pp.276-283
• /
• 2020

Alcohol-based solvents including ethanol (EtOH) and tert-butyl alcohol (TBA) are investigated instead of isopropanol (IPA), which is a common solvent for polytetrafluoroethylene (PTFE), as an alternative solvent for preparing the catalyst slurry with PTFE binder. As a result, the performance at 0.2 A/㎠ from the single cells from using catalyst slurries based on EtOH and TBA showed very similar value to that from the slurry using IPA, which implies the EtOH and TBA can be used as a solvent for the catalyst slurry. It is also confirmed by the very close values of the total resistance of the membrane electrode assemblies from the slurries using different solvents. In the energy dispersive spectrometry (EDS) image, the shape of crack and dispersion of PTFE are changed according to the vapor pressure of the solvent.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.45 no.5
• /
• pp.328-334
• /
• 2000

Sixty local soybean cultivars were evaluated on the antioxidative activity by superoxide dismutase (SOD), 1, 1-diphenyl-2-picrylhydrazyl (DPPH), thiobarbituric acid(TBA), and chemiluminescence using the FI-CL system. Soybean were collected throughout the country, and were grown over two years (1997 and 1998) for measuring antioxidative activity in soybean seeds. There were differences in antioxidative activity depen-ding on the method of measurement and variation of the crop year. Soybeans from Kwangyang-shi-1 (76.78%) in 1997 and Kangjin-gun-3(79.14%) in 1998 showed the highest SOD activity, whereas those from Hwasoon-gun (80.43%) in 1997 and Kangjin-gun-2 (49.82 %) in 1998 exhibited the highest DPPH activity. Soybeans from Chongup-gun-2 (75.77%) in 1997 and from Yochon-shi-5 (69.17%) in 1998 exhibited the highest TBA activity, and those from Jinahn-gun (48.99%) in 1997 and Kohung-gun (49.73%) in 1998 exhibited the highest activity using the chemiluminescence method. These results suggest that it may be possible to develop soybean varieties with higher antioxidative activity.

• Korean Journal of Veterinary Research
• /
• v.45 no.3
• /
• pp.341-350
• /
• 2005

To assess the antioxidative activity of 12 medicinal plants on lipid peroxidation, twelves traditional medicinal plants extracted with 95% methanol were investigated the antioxidative activity using DPPH, thiocyanate acid method, and thiobarbituric acid (TBA) methods. Out of 12 medicinal plants extracted with methanol, the extraction yields of Sedum kamtschaticum was the highest values (49.46%) among them and Geranicum sibiricum, Saururus chinensis root (R), Agrimonia pilosa leaf (L), Agrimonia pilosa root was the lowest value (9.97%). Radical scavenging effect of the selected traditional medicinal plants extracted from different extract solution were examined by 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical method. Antioxidative activity of methanolic extracts was higher than those of ethanol and n-hexane extracts. Scavenging effects in Sedum kamtaschaticum (R) determined by DPPH radical showed the highest among the 12 plants. The antioxidative effects of the first four medicinal plants were similar to those of butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT), but higher than that of tocopherol, which was used as a handled control. Antioxidative effects of each indicated concentration of the methanolic extracts on linoleic acid by thiocyanate method was the highest in Sedum kamtschaticum and followed by Geum japonicum and Agrimonia pilosa and their antioxidative effect were similar to those of BHA, and BHT, but higher than that of tocopherol. Antioxidative effects of the selected medicinal methanolic extract on linoleic acid by thiocyanate acid method were examined for 15 days. Peroxidation of control and tocopherol group occurred on days 5 and 9, respectively, but BHA, BHT, selected medicinal methanolic extract group did not occur until on day 15. Antioxidative effects of the selected medicinal methanolic extract on linoleic acid by TBA method were examined for 15 days. Antioxidative activity was similar to those obtained by thiocyanate acid method.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.30 no.3
• /
• pp.547-551
• /
• 2001

The comparative activities of acetone, ethanol, and aqueous fractions extracted from fruit powder of Cudrania tricuspidata by different temperature were tested by in vitro experimental models; peroxidation of linoleic acid and autooxidation of rat hepatic and renal microsomes by using thiobarbituric acid (TBA) for assay of free malondialdehyde production, and scavenging activities of free radicals by DPPH (α, α'-diphenyl-β-picrylhydrazyl). In DPPH method, acetone fraction extracted at 30℃ showed the highest free radical scavenging activities and acetone fractions extracted at 30℃ and 60℃ and ethanol fraction extracted at 30℃ showed stronger than BHT (butylated hydroxitoluene) although used ten-fold lower concentrations. In thiocyanate method used linoleic acid an inhibitory effects of all fractions showed higher than control treatment. TBA method used linoleic acid showed the highest antioxidative activity in acetone fraction extracted at 30℃ and 60℃. an inhibition activity against lipid peroxidation in hepatic microsomes of rats showed the highest at acetone faction extracted at acetone fraction among extracted fractions was shown to be the most potent antioxidative properties and this action was more potent in fractions extracted at 30℃ than those extracted at 60℃.