Validated HPTLC and HPLC methods for determination of fluorometholone and sodium cromoglycate in presence of their impurities and degradation products; application to kinetic study and on rabbit aqueous humor

Fluorometholone (FLM) and Sodium Cromoglycate (CMG) are co-formulated in ophthalmic preparation and showed marked instability under different conditions. Two specific, sensitive and precise stability-indicating chromatographic methods have been developed and validated for their determination in the presence of their degradation products and FLM impurity. Ten components were efficiently separated by them. The first method was HPTLC-spectrodensitometry, where the separation was achieved using silica gel 60?F₂₅₄ HPTLC plates and developing system of ethyl acetate: methanol (9:1, v/v). The second method was a reversed phase HPLC associated with kinetic study of the degradation process and was successfully applied for determination of the studied compounds in spiked rabbit aqueous humor. The mobile phase was acetonitrile: methanol: 0.05?M potassium dihydrogenphosphate (0.1% trimethylamine); pH 2.5, adjusted with orthophosphoric acid (20: 30: 50, by volume). In both methods, the separated components were detected at 240?nm and system suitability was checked. Good correlation was obtained in the range of 0.10–24.00 and 0.20–48.00?µg band^?1, for FLM and CMG by HPTLC. While for HPLC, the linearity ranges from 0.01–50.00 and 0.05–50.00?µg?mL^?1 for both drugs. The methods were applied in pharmaceutical formulation, where they were compared to the reported method with no significant difference.     

Corrected Debye-Hückel analysis of surface complexation; III. Spherical particle charging including ion condensation

Statistical mechanics has been used to derive a model for the charging of a spherical particle in a salt solution to complement our experimental studies and gain a deeper understanding of the processes involved in surface complexation. Our chosen model goes beyond the equilibrium constants and the Gouy-Chapmann theory currently used in surface complexation models. The proton adsorption is taken to occur at a harmonic potential well on the surface characterized by a frequency v and a well depth u(0). Outside the particle surface there is a capacitor layer of width w(c) which is impenetrable to the salt ions. The diffuse screening of the charged particle is described by a corrected Debye-Hückel analysis accounting for ion size in the ion-ion interactions. To account also for nonlinear electrostatic response a layer of condensed counterions has been introduced. The criterion for the onset of ion condensation is that the electrostatic field exceeds a linear response criterion. Ion size effects are accounted for in terms of hole-corrected electrostatic energies and excluded volume. The model has been applied to titrated surface charge data on goethite (alpha-FeOOH) at various background concentrations and good agreement between the experimental data and the model was obtained. Both the size of the screening ions and the central particle size were shown to be of importance for the surface charge.     

Thermoanalytical study of linkage isomerism in coordination compounds: Part I. Reinvestigation of thermodynamic and thermokinetic of solid state interconversion of nitrito (ONO) and nitro (NO2) isomers of pentaaminecobalt(III) chloride by means of DSC

Solid state thermal isomerization of [Co(NH₃)₅(ONO)]Cl₂ (nitrito isomer) to [Co(NH₃)₅(NO₂)]Cl₂ (nitro isomer) and reverse reaction were investigated by non-isothermal differential scanning calorimetry (DSC) and found to be essentially an equilibrium process. The interconversions are accelerated at above 65 °C and reach to equilibrium state at about 155 °C. After establishment of the equilibrium the relative amounts of two isomers at any temperature are governed by Gibbs free energy relationship. The experimental enthalpy changes of isomerization of pure nitrito and nitro solid samples to the equilibrium state are −4.67 (±0.19) and 0.99 (±0.05) kJ mol⁻¹, respectively. From these values, total enthalpy change was calculated as: ΔH°=−5.66(±0.20) kJ mol⁻¹. Using Gibbs free energy relationship, equilibrium constant, total free energy and entropy changes were estimated at 60 °C as: K=7.72(±0.8),  kJ mol⁻¹ and  J K⁻¹ mol⁻¹.An initial rate method has been developed to determine the kinetic parameters of these reactions from non-isothermal DSC data. Both nitro to nitrito and reverse reactions obey first order kinetic law in solid state. Estimated activation parameters of forward and reverse paths at 60 °C are , , and , respectively. The negative activation entropy of both directions support the intramolecular mechanism of isomerization, including formation of a seven coordinate transition state, which formerly suggested based on spectral and X-ray methods.     

Macrocyclic host cyclophosphazenes from aminolysis of N3P3CI6 by bis-(2-ortho-aminophenoxyethyl)ether

Aminolysis of N₃P₃CI₆ by an oxodiamine, bis-(2-ortho-aminophenoxyethyl) ether, has been carried out under various experimental conditions and new products with different architectures have been obtained. The reaction in diethyl ether when using a Na₂CO₃-water interface process gives the mono-BINO as major product. Reaction on Al₂O₃/KOH leads to the spirocyclic compound, while, when the reaction is carried out in toluene in the presence of NEt₃, a mixture of mono- and di-BINO products are obtained. These new products have been characterized by IR, ¹H and ³¹P NMR spectroscopy.      

Novel 1,2,3,4‐Tetrahydroquinazolinones via Reaction of 2‐Amino‐N‐substituted Benzamides and Dimethyl Acetylenedicarboxylate

Reaction of 2‐amino‐N‐substituted benzamides and dimethyl acetylenedicarboxylate (DMAD) in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in H₂O at room temperature led to the formation of novel 1,2,3,4‐tetrahydroquinazolinones.     

Synthesis and In Vitro Cytotoxic Activity of Novel Triazole‐Isoxazole Derivatives

New derivatives of triazole‐isoxazole were synthesized through a four‐step reaction starting from various ethyl 4‐aryl‐2,4‐dioxobutanoate derivatives. Finally, all compounds were examined by MTT assays for cytotoxic activity in two human breast cancer cell lines (MCF‐7 and T‐47D).     

A green one-pot synthesis of N-alkyl-2-(2-oxoazepan-1-yl)-2-arylacetamide derivatives via an Ugi four-center,three-component reaction in water

This work describes a green and efficient one-pot synthesis of N-alkyl-2-(2-oxoazepan-1-yl)-2-arylacetamide derivatives via an Ugi four-center, three-component reaction of 6-aminohexanoic acid, aromatic aldehydes, and isocyanide derivatives in water under reflux conditions in the absence of a catalyst.     

Radiochemical separation of99Mo from natural uranium irradiated with thermal neutrons

⁹⁹Mo was separated from uranium and insoluble fission product hydroxides. More than 98% of⁹⁹Mo radioactivity was extracted with bis (2-ethylhexyl)phosphoric acid. The organic phase was washed and⁹⁹Mo was back-extracted from the organic phase with NH₄OH solution. The percent recovery from the organic phase was 91% and the purity of⁹⁹Mo was more than 99%. Pure^99mTc was also extracted from the organic phase with a saline solution. Reversed-phase partition chromatography was used for the purification of⁹⁹Mo from¹³¹I and other fission products (10% HDEHP on kieselguhr bed).¹³¹I and other isotopes were quantitatively eluted with 0.1M H₂SO₄,⁹⁹Mo was eluted using a mixture of 0.5 M HCl and 30% H₂O₂.     

Photocatalytic Activity of Supported Metal Nanoparticles and Single Atoms

Photocatalysis has been known as one of the promising technologies due to its eco-friendly nature. However, the potential application of many photocatalysts is limited owing to their large bandgaps and inefficient use of the solar spectrum. One strategy to overcome this problem is to combine the advantages of heteroatom-containing supports with active metal centers to accurately adjust the structural parameters. Metal nanoparticles (MNPs) and single atom catalysts (SACs) are excellent candidates due to their distinctive coordination environment which enhances photocatalytic activity. Metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and carbon nitride (g-C₃N₄) have shown great potential as catalyst support for SACs and MNPs. The numerous combinations of organic linkers with various heteroatoms and metal ions provide unique structural characteristics to achieve advanced materials. This review describes the recent advancement of the modified MOFs, COFs and g-C₃N₄ with SACs and NPs for enhanced photocatalytic applications with emphasis on environmental remediation.     

Syntheses of 1-substituted 1,2,4-triazoles,imidazoles and benzimidazoles

Substituted 2-phenethyl-1,2,4-triazoles, 1-phenethylimidazoles 3 and 1-phenethylbenzimidazoles 5 were synthesized from the reaction of compound 8 with tri-n-butyltin hydride in good yield. The reaction of substituted-2-phenethyl halide with 1H-1,2,4-triazoles, imidazoles and benzimidazoles gave a low yield. The yield was increased by the use of substituted-2-phenethyl p-toluensulfonate.