Investigation of a Homologous Series of Fatty Acids by TLC. Part III. Application of Terms Describing the Separation of Homologous Series of Saturated Fatty Acids in TLC

JPC – Journal of Planar Chromatography – Modern TLC - Fatty acids from pentanoic to tricosanoic have been separated on RP-18 HPTLC plates, with and without concentrating zone, with...     

Kinetics and Characterization of Degradation Products of Dihydralazine and Hydrochlorothiazide in Binary Mixture by HPLC-UV,LC-DAD and LC–MS Methods

Dihydralazine and hydrochlorothiazide were stored at high temperature and humidity, under UV/Vis light and different pH, as individual drugs and the mixture. Then, a sensitive and selective HPLC-UV method was developed for simultaneous determination of dihydralazine and hydrochlorothiazide in presence of their degradation products. Finally, the degradation products were characterized through LC-DAD and LC–MS methods. Dihydralazine was sensitive to high temperature and humidity, UV/Vis light and pH?≥?7. At the same time, it was resistant to acidic conditions. Hydrochlorothiazide was sensitive to high temperature and humidity, UV/Vis light and changes in pH. Its highest level of degradation was observed in 1 M HCl. Degradation of the drugs was higher when they were stressed in the mixture. In the case of dihydralazine, the percentage degradation was 5–15 times higher. What is more, dihydralazine became sensitive to acidic conditions. Hydrochlorothiazide was shown to be more sensitive to UV/Vis light and pH?>?4. Degradation of dihydralazine and hydrochlorothiazide followed first-order kinetics. The quickest degradation of dihydralazine was found to be in 1 M NaOH while of hydrochlorothiazide was in 1 M HCl (individual hydrochlorothiazide) or at pH 7–10 (hydrochlorothiazide in the mixture). A number of new degradation products were detected and some of them were identified by our LC-DAD and LC–MS methods. In the stressed individual samples, (phenylmethyl)hydrazine and 1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide were observed for the first time. Interactions between dihydralazine and hydrochlorothiazide in the mixture were confirmed by additional degradation products, e.g., 2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1,4-trioxide.     

The study of the lipophilicity of alpha-(4-phenylpiperazin-1-yl)-gamma-phthalimidobutyramides using chromatographic and computational methods

The lipophilicity of the series of alpha-(4-phenylpiperazin-1-yl)-gamma-phthalimido-butyramides (1-8) has been investigated. Several methods, like reversed-phase thin-layer chromatography and high-performance liquid chromatography using reversed-phase RP18 and IAM.DD2 columns, were applied to determine RMO, log k0 and log k(0IAM) factors. The RP-TLC investigations were performed in mixtures of acetone-water and acetonitrile-water. For RP-HPLC method mixtures of acetonitrile, water and 0.01% TFA were used as the mobile phases while for IAM.DD2 investigations mixtures of acetonitrile and water were applied. The partition coefficients of compounds (1-8) were also calculated with the Pallas and CAChe programs. All the obtained data, both from experimental methods and computational calculations, were compared and a suitable conclusion was reached.     

Tuning properties of silver particle monolayers via controlled adsorption-desorption processes

Nanoparticle self-assembly at fluid-fluid interfaces has been traditionally exploited in emulsification, encapsulation and oil recovery, and more recently in emerging applications including functional nanomaterials and biphasic catalysis. We provide a review of the literature focusing on the open challenges that still hamper the broader applicability of this potentially transformative technology, and we outline strategies to achieve improved control over interfacial self-assembly of nanoparticles. First, we discuss means to promote spontaneous adsorption by tuning the interfacial energies of the nanoparticles with the fluids using capping ligands, and the occurrence of energy barriers. We then examine the interactions between interfacial nanoparticles and how they affect the formation of equilibrium interfacial suspensions versus non-equilibrium two-dimensional phases, such as weakly attractive glasses and gels. Important differences with colloidal interactions in a bulk suspension arise due to the discontinuity in solvent properties at the interface. For instance, ligand brushes rearrange in asymmetric configurations, and thus play a significant role in determining interparticle interactions. Finally, we briefly discuss the link between interfacial microstructure and the dynamic response of particle-laden interfaces, including interfacial rheology and the fate of nanoparticle monolayers upon out-of-plane deformation.     

Effect of the rhenium additive to VOx/TiO2 and MoOx/TiO2 catalysts on their properties in oxidative dehydrogenation of propane

VO_x/TiO₂ and MoO_x/TiO₂ catalysts with the addition of Re (Re/V or Mo = 0.5) were synthetized and tested in oxidative dehydrogenation of propane and in reduction by propane. XPS measurements showed depletion of the surface in Re. The Re additive does not affect the total conversion of propane, but increases the selectivity to propene. The effect is more pronounced for the MoO_x/TiO₂ catalyst. The increase in the selectivity to propene is accompanied with the increase in the reducibility of the catalysts.     

Application of Internal Standard for Micro Extraction– Spectrophotometric Determination of Bismuth in Pharmaceutical Formulations

 A micro extraction – spectrophotometric procedure is developed for the determination of bismuth in pharmaceutical formulations. The procedure is based on the extraction of tetraiodobismuthate(III) ion paired with benzyltributylammonium cation into chloroform. The application of Nile Blue as internal standard (IS) enabled good analytical performance for micro-scale analysis. The ratio between the absorbances measured at 491 nm (bismuth complex) and at 632 nm (IS) was taken as the analytical signal. The procedure was carried out in Eppendorf tubes, lowering significantly the use of reagents and the volume of organic solvent. In the calibration range up to 60 mgċl⁻¹, the linear regression coefficient was 0.9999, the CV for 15 mgċl⁻¹ and for 50 mgċl⁻¹ Bi were 1.6% and 0.7% respectively. The results obtained in the analysis of pharmaceutical formulations were in good agreement with the results of EDTA titration method. Received November 25, 1999. Revision February 14, 2000.     

Supplementation with Magnesium Salts—A Strategy to Increase Nutraceutical Value of Pleurotus djamor Fruiting Bodies

The use of substrates supplemented with minerals is a promising strategy for increasing the nutraceutical value of Pleurotus spp. The current research was performed to analyze the effect of substrate supplementation with magnesium (Mg) salts on the Mg content, biomass, and chemical composition of pink oyster mushroom (Pleurotus djamor) fruiting bodies. Before inoculation, substrate was supplemented with MgCl₂ × 6 H₂O and MgSO₄, both salts were applied at three concentrations: 210, 420, and 4200 mg of Mg per 2 kg of substrate. The harvest period included three flushes. Substrate supplementation with 4200 mg of Mg caused the most significant decrease in mushroom productivity, of about 28% for both Mg salts. The dry matter content in fruiting bodies was significantly lower in the treatment in which 210 mg of Mg was applied as MgSO₄ in comparison to the control. Supplementation effectively increased the Mg content in fruiting bodies of P. djamor by 19–85% depending on the treatment, and significantly affected the level of remaining bioelements and anions. One hundred grams of pink oyster fruiting bodies, supplemented with Mg salts, provides more than 20% of the Mg dietary value recommended by the Food and Drug Administration (FDA); thus, supplementation can be an effective technique for producing mushrooms that are rich in dietary Mg. Although P. djamor grown in supplemented substrate showed lower productivity, this was evident only in the fresh weight because the differences in dry weight were negligible. Mg supplementation increased the antioxidant activity of the fruiting bodies, phenolic compounds, and some amino acids, including L-tryptophan, and vitamins (thiamine and l-ascorbic acid).