• Korean Journal of Clinical Laboratory Science
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• v.36 no.2
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• pp.115-120
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• 2004

A bulk liquid membrane system was introduced for selective separation of an amino acid mixture. We confirmed p-diamethylaminobenzaldehyde (DAB), sulfosalicylic acid (SSA) and 1-naphtol were very useful carriers for selective separation of an amino acid mixture. As a result, Ala, Leu, Val, Phe and Ile were successfully separated by SSA, 1-naphtol in basic condition, 1-naphtol in weak acidic condition, DAB in strong acidic condition and DAB in strong basic condition. The separation mechanism was proposed by ion pair mechanism in the case of SSA and 1-naphtol and Imine bond formation mechanism was also introduced for DAB.

• Proceedings of the Ginseng society Conference
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• 1984.09a
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• pp.45-48
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• 1984

Ion-pair reverse phase HPLC techniques were used to compare the contents of IAA and IAAsp in the embryogenic and non-embryogenic calli derived from ginseng (Panax ginseng C.A. Meyer) root tissues. The contents of IAA and IAAsp of the embryogenic callus were much higher (7 to 18 X respectively) than those of non-embryogenic callus. There is a distinct fluorescent peak of an unknown component in the HPLC profile of the extract for indolic compounds from non-embryo-genic callus. This distinct difference may be employed as a promising parameter to screen the culture pieces for obtaining the calli with high potential for embryoid formation.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1951-1956
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• 2011

A kinetic study is reported on nucleophilic substitution reactions of 4-nitrophenyl nicotinate 5 and isonicotinate 6 with alkali metal ethoxide EtOM (M = K, Na, and Li) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. Plots of pseudo-first-order rate constant $k_{obsd}$ vs. EtOM concentration exhibit upward curvature for the reactions of 5 and 6 with EtOK and EtONa but are almost linear for those with EtOLi. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constant for the reaction with dissociated $EtO^-$ and ion-paired EtOM, respectively) has shown that $k_{EtOK}$ ${\geq}$ $k_{EtONa}$ > $k_{EtO^-}$ but $k_{EtOLi}$ < $k_{EtO^-}$. It has been concluded that $K^+$ and $Na^+$ ions catalyze the reactions by increasing the electrophilicity of the carbonyl carbon atom through formation of a 4-membered cyclic transition state $TS_3$ or $TS_4$. However, $M^+$ ion catalysis has been found to be much less significant for the reactions of 5 and 6 than for the corresponding reactions of 4-nitrophenyl picolinate 4, which was reported to proceed through a 5-membered cyclic transition state $TS_2$. Although 5 and 6 are significantly more reactive than 4-nitrophenyl benzoate 3, the reactions of 5 and 6 result in smaller $k_{EtOK}/k_{EtO^-}$ ratios than those of 3. The electron-withdrawing ability of the nitrogen atom in the acyl moiety of 5 and 6 has been suggested to be responsible for the increase in reactivity and the decrease in the $k_{EtOK}/k_{EtO^-}$ ratio.

• Membrane and Water Treatment
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• v.3 no.4
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• pp.221-230
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• 2012

This study employed the modified fouling index (MFI) to determine the performance of a two-step recycling system - a membrane filtration integrated laminar flow water storage (LFWS) tank followed by an ion exchange process to reclaim ultrapure water (UPW) from the wastewater generated from semiconductor wafer backgrinding and sawing processes. The first step consisted of the utilization of either ultrafiltration (UF) or nanofiltration (NF) membranes to remove solids in the wastewater where the second step consisted of an ion exchanger to further purify the filtrate. The system was able to produce high purity water in a continuous operating mode. However, higher recycling cost could be incurred due to membrane fouling. The feed wastewater used for this study contained high concentration of fine particles with low organic and ionic contents, hence membrane fouling was mainly attributed to particulate deposition and cake formation. Based on the MFI results, a LFWS tank that was equipped with a turbulence reducer with a pair of auto-valves was developed and found effective in minimizing fouling by discharging concentrated wastewater prior to any membrane filtration. By comparing flux behaviors of the improved system with the conventional system, the former maintained a high flux than the latter at the end of the experiment.

• Archives of Pharmacal Research
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• v.27 no.6
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• pp.670-675
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• 2004

Since the bitter taste of enrofloxacin apparently limit the patient compliance in the oral formulations of the antibacterial agent, the masking of the taste is essential for the improvement of the therapeutic effectiveness. Therefore, this study was carried out to examine the feasibility of taste masking of enrofloxacin by the retardation of its dissolution rate using the formation of complex between the drug and Carbopol. The complexation between Carbopol and enrofloxacin was confirmed by turbidity, UV spectrophotometry, wide angle X-ray diffraction, and differential scanning calorimetry. The enrofloxacin content in the complexes was 34％ （Carbo-enrofloxacin complex I） and 57％ （Carbo-enrofloxacin complex II） depending on the prepara-tion method. The dissolution rate of enrofloxacin from the complex increased as the pH was reduced. The dissolution rate of enrofloxacin from the Carbo-enrofloxacin complex I was significantly lower than that of the enrofloxacin powder. Therefore, these observations suggest that Carbo-enrofloxacin complex I can be used to mask the taste of enrofloxacin.

• Archives of Pharmacal Research
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• v.17 no.6
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• pp.415-419
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• 1994

A simple nad rapid colorimetric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate is described. The method is based on the interaction of the drug base with bromophenol blue to give a ion-pair complex. The spectra of the complex shows a maxima at 415-420 nm with high apparent molar absorptivities. Beer's law was obeyed in the concentration range 1-8, 2-10 and $2-12{\;}{\mu}{\cdot}ml^{-1}$ for amodiaquine hydrochloride, primaquine phosphate and chloroquine phosphate respectively. The proposed method was applied to the determination of these drugs in certain formulations and the results were favourably comparable to the official methods.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.434-437
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• 1991

Irradiation of 5-styryl-1,3-dimethyluracil (5-SDU) with 2,3-dimethyl-2-butene (DMB) gives a [4+2] cycloadduct which is converted into a [2+2] cycloadduct on the prolonged irradiation. Triplet sensitization, quenching, and external heavy atom effect on the [4+2] photocycloaddition reaction demonstrate the singlet pathway and salt effect excludes a radical ion pair precursor possibility. Polar solvents increase the reaction efficiency implying a polar exciplex involvement in the [4+2] photocycloaddition reaction. Inverse temperature dependence both on the reaction and DMB fluorescence quenching of 5-SDU indicates the presence of a singlet exciplex intermediate.

• Bulletin of the Korean Chemical Society
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• v.19 no.4
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• pp.439-444
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• 1998

The protonation of tetraphenylporphyrin (TPP) in acidic organic solutions was analyzed by acid titrimetric and temperature-dependent absorption measurements. Competition between the protonation of free base TPP $(TPPH_2)$ and the solvation of proton by near solvent molecules determines the equilibrium of the diprotonated TPP $(TPPH_4^{2+})$ formation. The diprotonated TPP exists as an ion pair complex with the acid counterions, which are found to affect the degree of red shift of the Soret band. The rotation of the phenyl rings also plays an important role in the diprotonation, as suggested by the decrease in the degree of diprotonation for the fluorophenyl TPP derivatives whose phenyl ring rotation is significantly hindered relative to normal TPP. The difference of fluorescence lifetime between $TPPH_2 \;({\pi}_{FL}=19.6\;ns)\; and\; TPPH_4^{2+} \;({\pi}_{FL}=2.1 \;ns)$ was used advantageously to measure the rate of protonation in the excited state. The protonation of TPPH2 are found to occur much slower than the diffusion of protons from bulk solution to the porphyrin ring. The monoprotonated TPP is suggested to be the transient species for the diprotonation process.

• Journal of the Korean Society of Clothing and Textiles
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• v.24 no.3
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• pp.422-428
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• 2000

At present, analytical methods available for determining the amount of cationic surfactants(DSDMAC) on the fabrics are spectrophotometric method based on formation and extraction of the colored ion pair with anionic dye, radiochemical analysis and HPLC analysis. This study presents new analytical methods based on the formation of cationic surfactant(DSDMAC)-disulfine blue complex on the cotton fabric. Test methods for determining the amount of DSDMAC-disulfine blue complex on the cotton fabrics are measuring the reflectance of the colored fabric and the absorbance of the methanol solution of DSDMAC-disulfine blue complex extracted from dyed cotton fabric. Linear relationships between the K/S value of the fabric treated with DSDMAC followed by disulfine blue and the amount of DSDMAC sorbed by cotton fabric were obtained. Thus, the amount of DSDMAC sorbed by cotton fabric can be determined by K/S value of the fabric. DSDMAC-disulfine blue complex on the cotton fabric was extracted with methanol. The amount of DSDMAC sorbed by cotton fabric was estimated by measuring the absorbance of the methanol solution extracted from dyed cotton fabric.

• Journal of the Korean Chemical Society
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• v.39 no.3
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• pp.143-149
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• 1995

At low concentration a simplified model of organic dye-surfactant system has been used to evaluate. By applying the resultant three parameter equation to the experimental data, values for the equilibrium constants for the ion-pair formation $(K_O)$, surfactant molecule addition to aggregates $(K_S)$ and dye aggregation reactions $(K_D)$ could be calculated and changes of free energy have obtained from its values. $K_O$ and K_S$ values were larger than those expected electrostatic interaction indicatihng a hydrophobic contribution and the $K_D$ values were about 10~20 times higher than those found for association in pure aqueous solutions which can be ascribed to the screening effect of the electrostatic repulsion.