• Journal of environmental and Sanitary engineering
• /
• v.14 no.3
• /
• pp.54-62
• /
• 1999

2,4-Dichlorophenol was known pollutants caused by the endocrine disruptor into the refractory substances of environment and this is difficult to be degradable by conventional methods. Therefore, a considerable interest has been devoted to developing new process where 2,4-Dichlorophenol can easily decomposed. In this study, the series of ultrasonic irradiation for removal of 2,4-Dichlorophenol has been selected as a model reaction in the batch reactor system in order to obtain the basic data investigate the influence of various experimental parameters such as concentration, pH, reaction temperature, acoustic intensity. The products obtained form the ultrasonic irradiation were analysed by GC/MS and HPLC. The formation of $H_2O_2$, a well-known the strong oxidant was found proportionally to increase with irradiation time. The intermediates of ultrasonic irradiation of 2,4-Dichlorophenol were identified as HCl, catechol, hydroquinone, o,p-benzoquinone, muconic acid, and maleic acid. The final products of this was $CO_2$ and $H_2O$. As the decomposition of 2,4-Dichlorophenol proceeds by the ultrasonic irradiation, the pH of 2,4-Dichlorophenol containing aqueous solution increases slowly, The decomposition of 2,4-Dichlorophenol was found to be occured fast in the basic medium. In general, the rate of reaction is proportional to the reaction temperature obeying the Arrhenius' law. However, in the ultrasonic irradiation, this suggests as the reaction temperature increase the decomposition rate of the reactant decreases. This result meant that the increase of reaction temperature due to the increase of vapor pressure of water accelerated the decrease of acoustic intensity which was can be proportional to the decomposition rae of these compounds. It was found that more than 80% of phenol solution was removed within hours in all reaction conditions. The reaction order in the degradation of the 2,4-Dichlorophenol compounds was verified as the Pseude-first order. From the fore-mentioned results, it can be concluded that the refractory organic compounds caused by endocrine disruptor as 2,4-dichlorophenol could be removed by the ultrasonic irradiation with radicals, such as $H{\;}{\cdot}{\;}and{\;}OH{\;}{\cdot}$ radical causing the high increase of pressure and temperature. Finally, it apeared that the technology using ultrasonic irradiation can be applied to the treatment of refractory substances caused by endocrine disruptor which are difficult to be decomposed by the conventional methods.

• Korean Journal of Food Science and Technology
• /
• v.26 no.6
• /
• pp.781-786
• /
• 1994

Meatlike flavors were manufactured using hydrolyzed vegetable protein (HVP) with several reactive precursors at different reaction conditions. Both pH and temperature affected significantly on brown colority of reaction product, whose velocity became fast with increasing pH and temperature. Drastic decrease in residual reducing sugars and free amino acids appeared until 1 hour, being little affected by reaction temperature. Glutamic acid and cysteine were decreased with reaction time, whereas glycine and methionine remained constant. Forty nine aroma compounds formed through Maillard reaction were isolated and identified with GC/MSD, including 3-methyl butanal, 2-methyl tetrahydrothiophen-3-one, 3,4-dimethylthiophene and 2,4-dimethyl thiazole previously known as natural meat flavors. The sensory evaluation showed that one-hour reaction product was the highest in savory taste and the lowest in nasty taste on the level of 5% significant difference among all reaction products tested in this experiment. From the results above, it could be speculated that the initial stage of Maillard reaction in this experimental system occured until one hour, thereafter, savory taste decreased accompanied by increasing nasty taste with elapsed reaction time.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.8
• /
• pp.2711-2716
• /
• 2011

para-Substituted phenoxide derivatives of Pd(II) having an NCN pincer, Pd(NCN)($OC_6H_4$-p-X) (NCN = 2,6-$(CH_2NMe_2)_2C_6H_3$; X = $NO_2$ (1), Me (2)) were prepared by the reaction of Pd(NCN)($OSO_2CF_3$) with equi-molar amount of $NaOC_6H_4$-p-X. Treatment of Pd(NCN)($OSO_2CF_3$) with an excess amount of $NaOC_6H_4$-p-Me affords the hydrogen-bonding adduct complex 3 ($2{\cdot}HOC_6H_4$-p-Me). Complex 3 can also be obtained from benzene solution of 2 in the presence of free $HOC_6H_4$-p-Me. Complex 1 does not undergo adduct formation with $HOC_6H_4-p-NO_2$ neither from metathesis reaction of Pd(NCN)($OSO_2CF_3$) with an excess amount of $NaOC_6H_4-p-NO_2$ nor from treatment of 1 with free $HOC_6H_4-p-NO_2$. Complex 3 undergoes fast exchange of the coordinated p-cresolate with the hydrogen-bonding p-cresol. Complex 2 undergoes ${\sigma}$-ligand exchange reaction with $HOC_6H_4-p-NO_2$ to give 1. The exchange reaction, however, is irreversible as readily anticipated from their respective $pK_a$ values of the phenol derivatives. Reaction of 2 with diphenyliodium chloride quantitatively produced Pd(NCN)Cl and PhI along with liberation of O-phenylated product $PhOC_6H_4$-p-Me which was identified by GC/MS spectroscopy.

• The Korean Journal of Pesticide Science
• /
• v.9 no.3
• /
• pp.237-242
• /
• 2005

This experiment was carried out to develop the fast and simple method for pesticide residue analysis by using solvent free solid injector (SFSI) and to validate the efficiency of the method developed for the residue analysis of the endocrine disruptor-like pesticides such as endosulfan, metribuzin, trifluralin and vinclozolin. The samples after freeze drying were sealed in glass capillary tubes and then introduced into the heated injector of gas chromatogaphy. The required pre-heating times were 1 min for endosulfan and trifluralin, 5 min for vinclozolin, and 10 min for metribuzin. The detection limits of endosulfan in chinese cabbages, metribuzin in lettuces, trifluralin in spinachs and vinclozolin in hot peppers were 0.05, 0.1, 0.05 and 0.05 ng, respectively and their recoveries were ranged from 74%, $98{\sim}107%$, $86{\sim}95%$ and $94{\sim}95%$, respectively. The detected level of metribuzine residue in field lettuce samples by using the SFSI was 0.6 ng/mg.

• Journal of the Korean Chemical Society
• /
• v.37 no.8
• /
• pp.711-716
• /
• 1993

The mechanism for electrochemical oxidation of natural alkaloid, ${\iota}$-sparteine (SP) was studied in acetonitrile solvent. The cyclic voltammogram of SP shows two irreversible anodic peaks at +0.75 V and +1.45 V vs. Ag/AgCl (0.1M AgNO$_2$ in acetonitrile) electrode. Coulometry reveals that the number of electrons involved in each oxidation peaks is in the range of 1.2∼1.3 respectively. Neutral imine radical was produced by fast deprotonation of SP radical cation formed by oxidation of one nitrogen atom in SP. Two pathways are possible for the reaction of the neutral radical: Due to the disproportionation of the radical, SP and enamine were mainly produced. Also, the 1,2-dehydrosparteinium cation was formed as minor product through the second one electron transfer oxidation of this radical. The (+)-lupanine was produced by treatment of sparteinium cation with potassium hydroxide. We have isolated and confirmed the electrolysis products using IR, GC-MS, UV-Vis, and thin-layer spectroelectrochemical method.

• The Journal of Korean Academy of Prosthodontics
• /
• v.41 no.6
• /
• pp.732-746
• /
• 2003

Statement of problem. Soft lining materials, also referred to as tissue conditioning materials, tissue heating materials, relining materials, soft liners or tissue conditioners, were first introduced to dentistry by a plastic manufacturer in 1959. Since the introduction of the materials to the dental field, their material properties have been continually improved through the effort of many researchers. Soft lining materials have become widely accepted, particularly by prosthodontists, because of their numerous clinical advantages and ease of manipulation. Unfortunately, few reports have been issued upon the topic of increasing the bond strength between the base metal alloy used in cast denture bases and PMMA soft liner modified with 4-META, nor upon the pattern of debonding and material change in wet environment like a intra oral situation. Purpose. The purposes of this study were comparing the bond strength between base metal alloy used for the cast denture bases and PMMA soft liner modified with 4-META, and describing the pattern of debonding and material property change in wet environment like the intraoral situation. Material and Methods. This study consisted of four experiments: 1. The in vitro measurement of shear bond strength of the adhesive soft liner. 2. The in vitro measurement of shear bond strength of the adhesive soft liner after 2 weeks of aging. 3. A comparison of debonding patterns. 4. An evaluation the Relation time of modified soft liner. The soft liner used in this study was commercially available as Coe-soft (GC America.IL.,USA), which is provided in forms of powder and liquid. This is a PMMA soft liner commonly used in dental clinics. The metal primer used in this study was 4-META containing primer packed in Meta fast denture base resin (Sun Medical Co., Osaka, Japan). The specimens were formed in a single lap joint desist which is useful for evaluating the apparent shear bond strength of adhesively bonded metal plate by tensile loading. Using the $20{\times}20mm$ transparent grid, percent area of adhesive soft liner remaining on the shear area was calculated to classify the debonding patterns. To evaluate the change of the initial flow of the modified adhesive soft liner, the gelation time was measured with an oscillating rheometer (Haake RS150W/ TC50, Haake Co., Germany). It was a stress control and parallel plate type with the diameter of 35mm. Conclusion. Within the conditions and limitations of this study, the following conclusions were drawn as follows. 1. There was significant increase of bond strength in the 5% 4-META, 10% 4-META containing groups and in the primer coated groups versus the control group(P<0.05). 2. After 2 weeks of aging, no significant increase in bond strength was found except for the group containing 10% 4-META (P<0.05). 3. The gelation times of the modified soft liner were 9.3 minutes for the 5% 4-META containing liner and 11.5 minutes for the 10% 4-META liner. 4. The debonding patterns of the 4-META containing group after 2 weeks of aging were similar to those of immediaely after preparation, but the debonding pattern of the primer group showed more adhesive failure after 2 weeks of aging.