摘要:

AbstractThe solvatochromic behavior of a penta‐tert‐butyl prydinium N‐phenolate betaine dye was studied using UV‐visible spectrophotometry in several binary mixture solvents. The solvent polarity parameter,ET(1) (kcal. mol−1) was calculated from the position of the longest‐wavelength intramolecular charge transfer absorption band of this penta‐tert‐butyl betaine dye.For binary solvent mixtures, all plots ofET(1) versus the mole fraction of a more polar component are nonlinear owing to preferential solvation of the probe by one component of the binary solvent mixture.In the computation ofET(1) it was assumed that the two solvents mixed interact to form a common structure with anET(1) value not always intermediate between those of the two solvents mixed. The results obtained are explained by the strong synergism observed for some of the binary mixtures with strong hydrogen bond donors (HBD) solvents s

ISSN:0009-4536    

DOI:10.1002/jccs.200600101

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractPiroxicam is a drug with analgesic and anti‐inflammatory properties. It is present in numerous pharmaceutical preparations. Injectable forms usually contain benzyl alcohol as an excipient, which is used as a blocking anesthetic (4%) and an antiseptic (4–10%). In this work, spectrophotometric methodology was used in order to determine benzyl alcohol in piroxicam injectable formulations by applying the fourth derivative method adopting the zero‐crossing technique. The results obtained show that the method has significant advantages over other reported methods and is appropriate for routine pharmaceutical analysis. The method showed excellent linearity in the range of 2–100 μg mL−1with limit of detection (S/N = 3) 0.07 μg mL−1(6.47 × 10−7M). The proposed method could be applied successfully for the determination of benzyl alcohol in injectable formulations with average % recove

ISSN:0009-4536    

DOI:10.1002/jccs.200600102

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractAn alternative method for solving homogenous and non‐homogenous differential equation systems used in chemical kinetics and pharmacokinetics on the basis of flow graph principles has been proposed. The classical method of solving these systems with flow graphs involves the employment of Laplace transform before depicting a flow graph and the inverse Laplace transform after using Mason's rules. A short description of flow graph algebra has been presented. One model very often encountered in pharmacokinetics was solved by both flow graph methods in order to make a comparison. Our proposed method is simpler and more direct, eliminating the Laplace transforms. The calculus is made directly on the base of the flow graph representing the image of reaction scheme (pharmacokinetic model

ISSN:0009-4536    

DOI:10.1002/jccs.200600103

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractWeakly bound linear and bent dimers, FH—X (where X = CO, OC, CNH, NCH, N2O and ON2), are investigated using the DFT B3LYP andab initioMP2 methods with the same basis sets (6–311++G(3df,2pd)). The strengths of the H—C or H—N H‐bonds in dimers FH—CO, FH—CNH, and FH—N2O are compared with those of the H—O or H—N H‐bonds in dimers FH—OC, FH—NCH, and FH—ON2. The results obtained for the H‐bond distances, the elongation effect of the HF bond, the red shift of the HF stretching frequency, and the energy difference between the dimer and the charge transfer reveal that the H‐bonds of the first group of dimers are stronger than those of the second. The Gibbs energies calculated for the six dimer formations indicate that the weakly bound dimers are unstable at room temperature (T = 2

ISSN:0009-4536    

DOI:10.1002/jccs.200600104

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe hydroconversion of cyclohexene (CHE) using monometallic catalysts containing 0.35wt% of Pt, Pd, Ir or Re on a γ‐alumina support, as well as bimetallic catalysts containing combinations of 0.35wt% Pt with 0.35wt% of either Pd, Ir or Re on γ‐alumina, were investigated in a plug flow‐type fixed‐bed reactor. The Cyclohexene (CHE) feed was injected continuously with a rate of 8.33 × 10−3mole h−1on 0.2 g of catalyst using a simultaneous hydrogen gas flow of 20 cm3min−1throughout a broad reaction temperature range of 50–400 °C. The dispersion of the metals in the catalysts was determined via H2or CO chemisorption. The activities of the monometallic catalysts were found to be in the order: Pd>Pt>Ir>Re, whereas those of the bimetallic catalysts were in the order: PtPd>PtIr>PtRe.Cyclohexene hydrogenation and dehydrogenation reactions using the current mono‐ and bimetallic catalysts were kinetically investigated applying the absolute reaction rate theory, whereby reaction rate constant, activation energy, enthalpy and entropy of activation were computed to explain surface variatio

ISSN:0009-4536    

DOI:10.1002/jccs.200600105

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe thermal reactions and photochemistry of monolayer methyl iodide (CH3I) on a silver covered TiO2(110) surface have been studied using combinative techniques of temperature programmed desorption (TPD) and x‐ray photoelectron spectroscopy (XPS). About ˜ 60% of CH3I at monolayer coverage on Ag/TiO2(110) dissociates between 130 and 200 K yield adsorbed CH3and I, with the rest desorbing molecularly at a peak temperature of 200 K in a TPD study. Photochemistry of CH3I on Ag/TiO2(110) is wavelength dependent. Irradiation of monolayer CH3I by 404 nm photon causes C‐I bond dissociation and CH3desorption. Upon 290 nm, UV irradiation, the depletion of CH3I(a)is dominated by photodesorption of molecular

ISSN:0009-4536    

DOI:10.1002/jccs.200600106

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractA multi‐channel surface acoustic wave (SAW) detection system which is employed to detect various organic molecules in a static system was prepared using 315 MHz one‐port quartz resonators and a home‐made computer interface for signal acquisition and data process. The oscillating frequency of the quartz crystal decreases on adsorption of organic molecules on the coating materials. The principal component analysis (PCA) method with SAS software was applied to select the appropriate coating materials onto the SAW crystals for organic vapors, e.g. hexane, 1‐hexene, 1‐hexyne, 1‐propanol, propionaldehyde, propionic acid, and 1‐propylamine. A dataset for a multi‐channel sensor with 19 SAW crystals for 7 analyses was collected after comparing the correlation between the 19 coating materials and the first six principal component (PC) factor. Furthermore, linear discriminate analysis (LDA) with SPSS software and a profile discrimination map were also applied and discussed for the discrimination of these organic vapors. These organic molecules could be clearly distinguished by the six‐channel SAW static sensor. The effect of concentration for various organic vapors was investiga

ISSN:0009-4536    

DOI:10.1002/jccs.200600107

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe undecanuclear copper cluster Cu11(μ9‐Se)(μ3‐I)3[Se2P(OEt)2]61, has been isolated along with Cu8(μ8‐Se)[Se2P(OEt)2]62, from the reaction of NH4Se2P(OEt)2, Cu(CH3CN)4PF6, and Bu4NI in a molar ratio of 3:2:2 in diethyl ether. The molecular formulation of1was confirmed by elemental analysis, positive FAB mass spectrometry, multinuclear NMR (1H,31P, and77Se), and X‐ray diffraction. In cluster1eleven copper atoms adopt the geometry of a 3,3,4,4,4‐pentacapped trigonal prism with a selenium atom in the center. The coordination geometry for the central, nonacoordinated selenium atom is tricapped trigonal prismatic. In addition, the central core Cu11Se is further stabilized by three iodides and six dsep ligands. Besides, weak inter‐molecular Se···I interactions (3.949–3.972 Å) are uncovered and form a one dimensi

ISSN:0009-4536    

DOI:10.1002/jccs.200600108

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThree simple, sensitive and accurate spectrophotometric methods have been developed for the determination of dextromethorphan hydrobromide (DEX) and ketamine hydrochloride (KET) in dosage forms. These methods are based on the formation of ion‐pair complexes with bromocresol green (BCG), bromocresol purple (BCP), and bromophenol blue (BPB) in acidic medium. The coloured ion‐pair products are measured at 419, 409 and 417 nm for DEX and at 417, 408 and 416 nm for KET using BCG, BCP and BPB, respectively. Beer's law was obeyed in the range of 2.0–22 μg mL−1for DEX and 2.0–16 μg mL−1for KET. The composition of the ion‐pair was established by continuous variation and molar ratio methods. The proposed methods were applied successfully for the determination of DEX and KET in dosage forms applying the standard addition technique and compared statistically with the official methods. The molar absorptivity, Sandell sensitivity, detection and quantification limits were

ISSN:0009-4536    

DOI:10.1002/jccs.200600109

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe electrochemical behaviors of formaldehyde (FA) at boron‐doped diamond (BDD) electrodes are investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear scanning voltammetry (LSV) techniques. The CV results show that the oxidation reaction of FA is influenced by the hydroxyl concentration in the solution, and the peak current response with the FA concentration is linear at the range from 10 to 100 mM. The differential capacitance from EIS results indicate that the FA molecules adsorb at the BDD electrode surface at low potential (from 1.0 to 1.4 V). The kinetic studies have been examined with the various concentrations of FA, pH, and temperature. The activation energy of FA oxidation is also calculated. The results of kinetic study indicate that the adsorption of FA molecules at the BDD electrode is the rate‐determining step at low potential (from 1.0 to 1.40

ISSN:0009-4536    

DOI:10.1002/jccs.200600110

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY