Measurement of Salicylic Acid by a High-Performance Liquid Chromatography Procedure Based on Ion-Exchange

An improved method for the detection and quantification of salicylic acid is described. This procedure utilised a high-performance liquid chromatography (HPLC) approach based on ion-exchange, coupled to a multi-detector system. This ameliorated the problems associated with resolution that are a characteristic feature of other methodologies. Furthermore, the increased sensitivity of this procedure supported a mini-scale format, which was both rapid and convenient. As the eluent from the ion exchange column was converted to water in the suppressor, this separation technique could also be linked directly to mass spectroscopy, providing more powerful characterization.     

Lanthanide(III) Complexes of Two Novel N 3 O 4 -donor Macrocycles Derived from 3,6-Dioxa-1,8-Octanediamine

Cyclodextrins are a group of cyclic oligosaccharides which have shown to improve pharmaceutical properties of drugs, such as solubility and stability, by forming inclusion complexes. Diloxanide furoate has direct amoebicide action on the intestinal lumen and little solubility in water. In this work, solubility, NMR, fluorescence techniques, and kinetic methods were used to determine the equilibrium constant for the formation of the -cyclodextrin–diloxanide furoate complex, K_1:1. It is shown that the kinetic approach is the best method for such a determination.     

Novel temperature-sensitive, β-cyclodextrin-incorporated poly(N-isopropylacrylamide) hydrogels for slow release of drug

Novel temperature-sensitive poly(N-isopropylacrylamide) hydrogels containing water-soluble -cyclodextrin polymer were prepared by forming semi-interpenetrating polymeric networks. Compared to the conventional poly(N-isopropylacrylamide) gel, the -cyclodextrin-incorporated hydrogels showed the same lower critical solution temperature due to the independence of the -cyclodextrin polymer in the networks. The release time of ibuprofen from the novel gel was significantly prolonged, which was presumably attributed to the formation of the inclusion complexes between the cyclodextrin groups and the drug molecules.Jian-Tao Zhang and Shi-Wen Huang have contributed equally to this work.     

Theoretical Study for Alcoholysis of <Emphasis Type="Italic">N</Emphasis>-Benzyl 3-Oxo-β-Sultam

The alcoholysis mechanisms of N-benzyl 3-oxo--sultam are investigated at B3LYP/6-31G* level. Different possible mechanistic pathways of the reaction are proposed. The results show that the cleavage of S–N bond producing P1 has a little lower energy barrier than does C–N bond producing P2. The inclusion of solvent effects by a polarizable continuum model (PCM) does not change the conclusions based on the gas-phase study.     

Proton-neutron configurations in 236g, mAm and its EC-decay daughter 236Pu

The EC decay of ²³⁶Am has been studied using a gas-jet coupled on-line isotope separator. A half-life analysis revealed that there are two EC-decaying states in ²³⁶Am: the 5^- state with T_1/2 = 3.6(2) min and the (1^-) state with T_1/2 = 2.9(2) min. The 1185.5 keV level in ²³⁶Pu was found to be the K isomer with K = 5^- and t_1/2 = 1.2(3) s. EC transitions from ^{236g, m}Am to the 1185.5, 1311.5, and 1340.8 keV levels in ²³⁶Pu show small log ft values of 4.9, 5.3, and 4.8, respectively, indicating that the 5/2⁺[642] 5/2⁺[633] transition largely contributes to these transitions, and thus, the populated levels should be the 5/2^-[523]5/2⁺[642] two-quasiparticle states. The K = 0^- octupole band established in ²³⁶Pu is located at higher energy than those in ^238,240Pu, which implies that the octupole correlations become weak at ²³⁶Pu.     

The neutron decay retardation spectrometer aSPECT: Electromagnetic design and systematic effects

The apparatus described here, aSPECT, will be used for a measurement of the neutrino-electron angular correlation coefficient a in the decay of free neutrons. The idea of the aSPECT spectrometer is to measure the integrated proton energy spectrum very accurately using an energy filter by electrostatic retardation and magnetic adiabatic collimation. The main ideas of the spectrometer are presented, followed by an explanation of the adiabatic transmission function. Details of the superconducting coil and of the electrode system are given, as well as a discussion of the most important systematic effects: magnetic field and electrostatic potential inhomogeneities, deviation from adiabatic motion, scattering in the residual gas, background, Doppler effect, edge effect, and detector efficiency. Using this spectrometer, the parameter a is planned to be measured with an absolute experimental uncertainty of a 3 ^. 10^-4, from which the axial vector to vector coupling constant ratio can be determined with an accuracy of 0.001.     

Search for tensor couplings in the weak interaction

The existence of exotic couplings in the weak interaction can be tested by a precise measurement of the β-ν angular correlation parameter a in nuclear beta decay. In the case of ⁶He, the ratio of tensor and axial-vector couplings can be determined. The goal of the LPC Trap experiment is to improve the limits on the existence of tensor currents. The LPCTrap setup is installed on the low energy beam line LIRAT of the SPIRAL/GANIL facility. The ⁶He⁺ ions are confined in a novel transparent Paul trap allowing the detection in coincidence of both the β-particle and the recoil ion. The detection setup enables to detect the position and energy of these two particles. The a parameter can then be extracted from the time of flight spectrum of the recoil ions. The first ⁶He⁺ decay events were observed in May 2005 during a commissioning run. Over 10⁵ coincidence events have been recorded during a second run in July 2006.     

New 1,4-dihydropyridine derivatives with hetero and saturated B rings

The single crystal structures of 4-(5-(1,3-benzodioxole)-2,6-dimethyl-1,4-dihydropyridine-3,5-bis(methoxycarbonyl) (I), 4-(3-pyridyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-bis (methoxycarbonyl) (II), 4-(3(1-methyl-1H-indole))-2,6-dimethyl-1,4-dihydropyridine-3, 5-bis(methoxycarbonyl) (III), and 4-cyclopentadienyl-2,6-dimethyl-1,4-dihydropyridine-3,5-bis(methoxycarbonyl) (IV) suggest that these members of a calcium beta blocking family may dock with their receptor sites from the A ring end of the molecule.     

Electrochemical Hydrogenation of Acetophenone and Methyl-4-isobutylacetophenone in a Two-phase Water–Organic System Containing β-Cyclodextrin

The possibility of the formation of inclusion complexes based on methyl-4-isobutylphenyl ketone, -cyclodextrin (-CD), and o-hydroxy propylated -cyclodextrin in an aqueous phosphate buffer is demonstrated by methods of NMR spectroscopy and cyclic voltammetry. Preparative electroreduction of acetophenone and methyl-4-isobutylphenyl ketone is performed on a lead electrode in aqueous phosphate and acetate buffers in the absence and presence of -CD and the composition of products of electrochemical reactions is ascertained. It is shown that the products of reduction of ketones are corresponding alcohols and pinacones. The possibility of asymmetric electrochemical hydrogenation of ketones in the presence of -CD, which yields relevant chiral alcohols, is shown.     

Fluoroalkyl-containing lithium β-diketonates in the synthesis of 1,2,4-triazolo[1,5-a]pyrimidines

Cyclocondensation of fluorine-containing lithium -diketonates with 3-amino-1,2,4-triazoles afforded 7-fluoromethyl-1,2,4-triazolo[1,5-a]pyrimidines.