• Archives of Pharmacal Research
• /
• v.14 no.4
• /
• pp.285-289
• /
• 1991

A convenient spectrophotometric method was examined for the determination of amantadine sulfate (AMTS) which has no UV-VIS chromopohores. AMTS was ion-paired quantitatively with methyl orange (MO) at $70^{\circ}C$ for 30 min. The ion-paired complex was extracted with dichloromethane and the absorbance was measured at 421.5 nm. A linear relationship was observed in the range of $2.5{\times}10^{-7}\;M$ to $3.75{\times}10^{-6}\;M$ and the correlation coefficient was 0.999 (n=3). This assay method was applied to the quantification of AMTS in commercial tablet form with good recovery and high precision.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.333-333
• /
• 2011

We studied the H/D exchange kinetics of pure and acid dopped water-ice film by using the techniques of reactive ions scattering (RIS) and low energy sputtering (LES) with low kinetic energy cesium ion beam (<35 eV). From RIS, neutral water isotopomers were detected in the form of cesium-molecule ion clusters, $CsX^+$ (X= $H_2O$, HDO, $D_2O$). Ionic species, like $H_3O^+$, $DH_2O^+$, $D_2HO^+$, $D_3O^+$, adsorbed on the surface were ejected via LES process. Those techniques allowed us to trace the isotopomeric populations of water-ice film. To show the catalytic effect of excess proton in the H/D exchange reaction, our study was conducted with two types of water-ice films. In film 1, about 0.5 BL of $H_2O$ was adsorbed on HCl (0.1 ML) dopped $D_2O$ (8 BL) film. In film 2, similar amount of $H_2O$ used in film 1 was adsorbed on pure $D_2O$ film. Kinetic data were obtained from each film type for 90-110 K (film 1) and 110-130 K (film 2) and fitted with numerically integrated lines. Through the Arrhenius plot of kinetic coefficient deduced from fitting of the H/D exchange reaction, the activation energy of film 1 and 2 were estimated to be $10{\pm}3kJmol^{-1}$ and $17{\pm}4kJmol^{-1}$. This activation barrier difference could be understood from detailed pictures of H/D exchange. In film 2, both the formation of ion pair, $H_3O^+$ and OH. and proton transfer were needed for the H/D exchange. However, in film 1, only proton transfer was necessary but ion pair formation was not, so this might reduce the activation energy.

• Journal of applied mathematics & informatics
• /
• v.5 no.2
• /
• pp.449-456
• /
• 1998

In this paper a new type of t-operators with double threshold a,b,$\in$(0,1). a$\leq$b, is presented, each pair (t-norm, t-conorm) consisting of two dual elements with respect to a negation with double threshold.

• Bulletin of the Korean Chemical Society
• /
• v.11 no.1
• /
• pp.77-78
• /
• 1990

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.23 no.3
• /
• pp.161-167
• /
• 1997

Determination of several cationic surfactants in cosmetics has been investigated. Reverse phase ion pair chromatography was used to identify and quantitate cationic surfactants. Cationic surfactants analyzed in this experiment were cetylpyridium chloride, stearyltrimetylammonium chloride, bezalkonium chloride, benzyldicethylcetylammonium chloride, and bihenyltrimethyl ammonium chloride. The separation was achieved on a reverse phase coumn with 10mM HCl-acetonitrile eluent. In this condition, the most of cationic surfactants with exception of CPC and CTAC respectively with suppressed conductivity detector and UV detector connected in series. The calibration curves obtained by plotting the peak areas of the cationic surfactants were linear at levels ranging from 0.005 to 0.1% correlation coefficient, r=0.9988. The detection limits were 1 to 5ppm in sample solution. The average recoveries of cationic surfactants added to hair treatment cream and hair rinse in three to five experiments were 96.7 105.2% and relative standard deviations were 1.1-3.8%. The case that there were CPC and CTAC in same solution was also tested. CPC and CTAC which couldn't be separated on reverse phase column were quantitated with suppressed conductivity detector and UV detector connected in series. Recovery of CPC and CTAC were 101.6 and 89.2% respectively. The proposed method was applied to the determination of cationic surfactants in commercial hair treatment cream.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.6
• /
• pp.1814-1822
• /
• 2013

By using density functional theory calculations, we have performed a systemic study on the electronic structures and topological properties of interactions between N-butylpyridinium nitrate ($[BPY]^+[NO_3]^-$) and thiophene (TS), benzothiophene (BT), dibenzothiophene (DBT), naphthalene (NAP). The most stable structure of $[BPY]^+[NO_3]^-$ ion pair indicates that hydrogen bonding interactions between oxygen atoms on $[NO_3]^-$ anion and C2-H2 on pyridinium ring play a dominating role in the formation of ion pair. The occurrence of hydrogen bonding, ${\pi}{\cdots}$H-C, and ${\pi}{\cdots}{\pi}$ interactions between $[BPY]^+[NO_3]^-$ and TS, BT, DBT, NAP has been corroborated at the molecular level. But hydrogen bonding and ${\pi}{\cdots}{\pi}$ interactions between $[BPY]^+[NO_3]^-$ and NAP are weak in terms of structural properties and NBO, AIM analyses. DBT is prior to adsorption on N-butylpyridinium nitrate ionic liquid.

• Publications of The Korean Astronomical Society
• /
• v.10 no.1
• /
• pp.79-90
• /
• 1995

The unique compact radio source, Sgr $A^*$, at the Galactic center show many observational signs that it is powered by supermassive black hole. Recent observations also imply that it is surrounded by winds from nearby IR sources. So we explore the model in which multiwavelength spectrum from Sgr $A^*$ is due to the spherical accretion of these winds onto the central supermassive black hole. Improving upon the previous work, we allowed the possibility that ions and electrons have different temperatures, included the Compton effects and pair processes. Electrons radiate via cyclosynchrotron and bresstrahlung with comptoniztion. We find that ion approaches the virial temperature ${\sim}10^{13}K$ while electron temperature saturates at ${\sim}10^{10}K$. However, decoupling between ion and electron does not greatly affect the shape of the emission spectrum. When the mass of the black hole is ${\sim}10^6M_{\odot}$, radio, IR, X-ray, $\gamma$-ray band spectrum is reasonably explained by the model. Yet Compton effect which is neglected in previous works produces significant emission in IR band, which is marginally compatible with observations. Pair production is negligible and annihilation lines cannot be observed.

• Journal of Pharmaceutical Investigation
• /
• v.21 no.3
• /
• pp.171-177
• /
• 1991

A reverse-phase, ion-pair high performance liquid chromatographic (HPLC) method for the simultaneous quantative determination of pyridostigmine and its hydrolytic product, 3-hydroxy-N-methylpyridinium (HMP), is descrihed, The assay of pyridostigmine and HMP was linear in the range of amount from 24 to 60 mg/tablet and from 2.4 to 12.0 mg/tablet, respectively, with coefficient of variation (C.V.) of 0.05-0.12% (n=7) and 0.25-0.52% (n=5), respectively, and applicable conveniently even in the case of the mixture of pyridostigmine and HMP. Meanwhile, the conventional UV method gave inaccurate results for the aged pyridostigmine tablets. In the extraction of pyridostigmine from tablets prior to be assayed by HPLC, methanol was found to be more effective than ethanol or distilled water. Multiple extraction (four times) with methanol resulted in the full recovery of pyridostigmine, whereas ethanol gave 95% recovery even after four times extraction. Based on these results. the present method would be very useful for the accurate determination of pyridostigmine in the aged pyridostigmine tablets.

• Analytical Science and Technology
• /
• v.15 no.3
• /
• pp.190-195
• /
• 2002

We analysed mutation of ${\beta}_2$-adrenergic receptor gene that controls bronchial asthma by denaturing high performance liquid chromatography (DHPLC) according to ion-pair reversed-phase high performance liquid chromatography (IP-RP-HPLC). We extracted genomic DNA from 50 asthma patients, amplified DNA using PCR, and analysed PCR product by DHPLC. As a result, we obtained that mutation frequency was 15 (30%) among 50 cases. Consequently DHPLC mutation detection was confirmed that the result of direct sequencing was coincide exactly.

• Journal of the Korean Chemical Society
• /
• v.28 no.3
• /
• pp.176-184
• /
• 1984

Retention behavior of benzoic acid and its derivatives on XAD-2 in the alcoholic aqueous solution was investigated and separation was attempted. Retention was affected by the concentration and kinds of added organic solvents, the pH of the aqueous solution, the added $R_4N^+$ and the position and kinds of functional group in the sample molecules. Retention of sample acids in acidic conditions was due to mainly molecular adsorption on nonpolar XAD-2 surface and that in basic conditions was due to mainly ion-pair model. In these bases a mixed sample was separated in EtOH 20% aqueous solution at pH 8.50.