the effect of sds (0.03-0.07 m) and brij-35(0-0.003 m) concentrations and temperature on retention parameters of 30 solutes in micellar reversed- phase liquid chromatography systems were studied using solvation parameter model. the system constants were determined by multiple linear regression analysis from experimental values of the retention factors with known descriptors by computer using th...

Benzo[b]cyclohexa-2,4-dien-1-one (4) and benzo[b]cyclohexa-2,5-dien-1-one (5), the two most stable keto tautomers of 1-naphthol (1), were generated in aqueous solution by Norrish Type II fission of 4- and 2-phenacyl-1-tetralone, respectively, and the pH-rate profiles of their enolization were measured by flash photolysis. Several isotopic exchange rates of 1 were measured in aqueous acid to det...

Roasting has considerable effects on the quality of cream made of nuts. In this study, the roasting conditions of walnut kernels were optimized based on the stability parameters of the produced cream. Temperatures of 100-150°C for 10-30 minutes were used to roast walnut kernels. The amount of oil separation, peroxide, acidity and Thiobarbituric acid values of the cream, as well as color paramet...

a competitive spectrophotometric method has been used for the study of complexation between cu2+, zn2+ and cd2+ (m) and 18-crown-6(18c6, b) in methanol using 4-(2-thiazolylazo) resorcinol (tar, hl) as the colorimetric complexant. absorption spectra of the species in the m-tar-18 c6 system at a various concentrations of 18c6 showed no formation of ternary complex, mlb, and the stoichiometry of t...

Countercurrent chromatography (CCC) is a liquid chromatography technique in which the stationary phase is also a liquid. The solute separation is based on partitioning between the two immiscible liquid phases: the mobile phase and the support-free liquid stationary phase. Octanol-water partition coefficients (Po/w) of 17 βblockers and 17 sulphonamides were determined by CCC. Some of the Po/w co...

BACKGROUND Cyanoform is long known as one of the strongest acid. Cyanoform is only stable below -40 °C. The issue of the stability and tautomeric equilibria of cyanoform (CF) are investigated at the DFT and MP2 levels of theory. The present work presents a detailed study of structural tautomer interconversion in three different media, namely, in the gas phase, in a solvent continuum, and in a m...

Heterogeneous catalytic hydrogenation of cyclohexene, catalyzed by Pt/A1203, was carried out in thirteenvarious solvents (four alcoholic solvents, six aprotic polar solvents and three non polar solvents) at 25 °C.Single-parameter correlations of logk vs. normalized polarity parameter (ETN), hydrogen-bond acceptorbasicity (p), hydrogen-bond donor acidity (a) and dipolarity/polarizibility (it*) d...

the aim of this study was to evaluate the effects of echinophora cinerea boiss and stachys lavandulifolia vahl extracts on quality and sensory properties of doogh, as a dairy drinking, to enhance public health society. for this purpose, different levels of each plant extract was added to the doogh. stability, acidity, ph, microbial and sensory properties of doogh samples were studied during 45 ...

The acidity constants of eight macrolides (erythromycin, roxithromycin, oleandomycin, azithromycin, josamycin, tylosin tartrate, tilmicosin and spiramycin) have been determined in acetonitrile-water binary mixtures (30%, 40% and 50% (v/v)) by spectrophotometric method. The pKa's available in literature determined by various methods are compiled in comparison with the value of this work. These r...

The formation constants of the species formed in the systems H+ + thallium(I) + AMP and H+ + AMP have been determined in aqueous solutions of methanol at 25 degrees C and constant ionic strength 0.1 mol dm(-3) sodium perchlorate, using spectrophotometric and potentiometric techniques. Thallium(I) forms two mononuclear 1:1 complexes with AMP of the type TlHL and TlL- in the pH range of study (1-...