High-Performance Thin-Layer Chromatographic Determination of Itopride Hydrochloride in its Pharmaceutical Preparation and in the Bulk Drug

JPC – Journal of Planar Chromatography – Modern TLC - A normal-phase high-performance thin-layer chromatographic (HPTLC) method has been established for quantitative estimation of...     

Reactive blends derived from modified soybean oil and silicone

Reactive blends prepared from methoxysilane terminated silicone polymers and silylated soybean oil are described and characterized. Although simple mixing of soy and silicones results in gross phase separation, homogeneous polymeric products are obtained by introducing reactive sites. These products can be used as protective coatings, additives to adhesives and new sealants. Exposure of the mixtures to moisture leads to hydrolysis of the methoxysilanes and subsequent condensation of the resulting silanols that yields stable siloxane linkages between the two immiscible phases. FTIR, TGA, and swell‐gel analyses indicate effective formation of these siloxane crosslinks. Reactive blends containing less than 20% silylated oil appeared completely transparent but increasing the soy content decreased the optical transparency. SEM micrographs reveal the silicone polymer as the continuous phase with individual spherical silylated soy oil particles distributed in it. The properties of these reactive blends vary from high elongation elastomers to high modulus resins depending on the composition. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3086–3093     

Obtaining functional form for chaotic time series evolution using genetic algorithm

A genetic algorithm (GA) based strategy is presented for deducing an exact or near-exact functional form from a time series. The GA formalism proposed here utilizes (i) the "postfix" representation with a view to reduce the procedural complexities and (ii) the "elitist mating" scheme to produce fitter offspring strings. The GA procedure is exemplified by considering chaotic time series of the well-known logistic, Henon and universal maps. The GA correctly recovers the underlying functional forms for the respective time series. Measurements from a number of finite-dimensional physical, biological, and other systems often give rise to complex time series and the presented methodology should prove useful in obtaining functional forms describing accurately the evolution of the time series. (c) 1999 American Institute of Physics.     

Analysis of viscoelastic behavior and dynamic mechanical relaxation of copolyester based layered silicate nanocomposites using Havriliak–Negami model

The solid‐state viscoelastic properties are examined for intercalated nanocomposites based on a copolyester and (2‐ethyl‐hexyl)dimethyl hydrogenated‐tallow ammonium montmorillonite. The nanocomposites are prepared via the direct melt intercalation technique using a conventional twin‐screw extruder. Dynamic mechanical thermal analysis of the nanocomposites is conducted using two different test setups. The dynamic mechanical relaxation spectra show an increase in the storage modulus of the nanocomposite over the entire temperature range under study as compared to the pristine polymer (except in the transition region from 70 to 80 °C). These results are analyzed using the empirical Havriliak–Negami (HN) equation. The four temperature independent HN parameters (α, β, E₀, and E_∞) and one temperature dependent parameter (τ, the relaxation time) are determined by solving the HN equation for each temperature over the range of temperatures. The calculated moduli results fit well with the experimental values of the relaxation spectra for the nanocomposites. This study shows that the HN model can be applied to polymer layered silicate nanocomposites, and it can be used to predict their dynamic mechanical properties over a wide range of temperatures and frequencies a priori. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2657–2666, 2004     

Photopolymerization of bis-aromatic and alicyclic based solid urethane acrylate macromonomer in the presence of large excess of reactive diluent

A solid urethane acrylate macromonomer with bis-aromatic as well as alicyclic moieties was synthesized and the kinetics of photopolymerization reactions were studied in the presence of varying concentration of photoinitiator and large excess of reactive diluent using photo DSC. The studies show that the rate of maximum polymerization was found to increase with increase in concentration of photoinitiator while a decrease was observed by an increase in temperature. The final conversion showed a decrease at highest isothermal condition due to vitrification. Estimation of kinetic parameters including applicability of autocatalytic and modified autocatalytic models were investigated by nonlinear regression. It was observed that the modified models gave a better fit with the experimental data and kinetic parameters showed a decrease with increase in temperature and an increase with increase in concentration of photoinitiator.     

Pumice-based sulfonic acid: a sustainable and recyclable acidic catalyst for one-pot synthesis of pyrazole anchored 1,4-dihydropyridine derivatives at room temperature

Research on Chemical Intermediates - In the present investigation, we have developed an efficient and eco-friendly protocol for the synthesis of pyrazole anchored 1,4-dihydropyridine analogs using...     

High-performance liquid chromatographic determination of cyclohexylhydantoin and cyclohexylidenehydantoin formed during the synthesis of phenylhydantoin from hydantoin and cyclohexanone

-Phenylhydantoin can be converted into -phenylglycine by an enzymatic process. -phenylglycine is an important starting material in the production of β-lactams such as semisynthetic penicillins and cephalosporins. In our laboratory, the synthesis of phenylhydantoin was achieved from hydantoin and cyclohexanone in the presence of a base. An efficient and fast isocratic reversed-phase high-performance liquid chromatography method was developed for the determination of phenylhydantoin, cyclohexylhydantoin and cyclohexylidenehydantoin. Quantitative analysis was carried out by an external standard method.     

Thermodynamic approach to enhance the dispersion of graphene in epoxy matrix and its effect on mechanical and thermal properties of epoxy nanocomposites

Graphene-reinforced polymer nanocomposites are under intense investigation in recent years. In this work, graphene nanosheets have been prepared using chemical reduction method of graphene oxide. Graphene-reinforced epoxy nanocomposites show an enhancement in mechanical and thermal properties at 0.05 wt.% of graphene in epoxy matrix. Modification of graphene with polyvinylpyrrolidone (PVP) shows the significant enhancement in mechanical and thermal properties of epoxy nanocomposites. PVP-modified graphene nanosheets reduces the gap of enthalpic and entropic penalties and facilitates improved dispersion of graphene in epoxy matrix. In addition, enhanced dispersion of PVP-modified graphene in epoxy matrix results in better load transfer across graphene–epoxy interface. Glass transition temperature (T_g) of PVP-modified graphene epoxy nanocomposites increases as compared to pure epoxy because there exist an interaction between epoxy and PVP. Fractography study reveals the localized ductile fracture.     

Simple and Sensitive Extractive Spectrophotometeric Method for the Assay of Mebeverine Hydrochloride in Pure and Pharmaceutical Formulations

Simple, sensitive, rapid and cost effective extraction spectrophotometric methods are described for the assay of mebeverine hydrochloride (MBH) in bulk samples and pharmaceutical formulations. These two methods (Bromophenol blue and Erichrome Black‐T) are based on the formation of chloroform soluble ion‐pair complexes of MBH with Bromophenol blue (BPB) and with Erichrome Black‐T (EBT), to form yellow and pink colored chromogen in a Glycine‐HCl buffer of pH 2.4 (BPB) and in a KCl‐HCl buffer of pH 1.4 (EBT) with absorbance maximum at 416 nm and at 524 nm for BPB and EBT respectively. The calibration graph is found to linear over 0.2–20 μg/mL (BPB) and 0.2–20 μg/mL (EBT), with molar absorptivity values of 1.8295 × 10⁴ 1 moL^?1 cm^?1 and 1.5896 × 10⁴ 1 moL^?1 cm^?1, respectively. The LOD (Limit of Detection) were found to be 0.090 μg/mL and 0.084 μg/mL and LOQ (Limit of Quantification) were 0.2997 μg/mL and 0.2730 μg/mL for the BPB and EBT method, respectively. The results of analysis for the two methods have been validated statistically and by recovery studies. The results are compared with those obtained with reported method. The proposed methods are simple, sensitive, accurate and suitable for quality control applications.     

Inherent stability testing of empagliflozin in the presence of metformin HCl by HPTLC and characterization of degradation products of empagliflozin by LC–ESI–QTOF–MS/MS

JPC – Journal of Planar Chromatography – Modern TLC - A successful attempt has been made to develop and validate a stability-indicating high-performance thin-layer chromatography...