Quality‐by‐design‐based ultra high performance liquid chromatography related substances method development by establishing the proficient design space for sumatriptan and naproxen combination

Quality‐by‐design‐based methods hold greater level of confidence for variations and greater success in method transfer. A quality‐by‐design‐based ultra high performance liquid chromatography method was developed for the simultaneous assay of sumatriptan and naproxen along with their related substances. The first screening was performed by fractional factorial design comprising 44 experiments for reversed‐phase stationary phases, pH, and organic modifiers. The results of screening design experiments suggested phenyl hexyl column and acetonitrile were the best combination. The method was further optimized for flow rate, temperature, and gradient time by experimental design of 20 experiments and the knowledge space was generated for effect of variable on response (number of peaks ≥ 1.50 – resolution). Proficient design space was generated from knowledge space by applying Monte Carlo simulation to successfully integrate quantitative robustness metrics during optimization stage itself. The final method provided the robust performance which was verified and validated. Final conditions comprised Waters® Acquity phenyl hexyl column with gradient elution using ammonium acetate (pH 4.12, 0.02 M) buffer and acetonitrile at 0.355 mL/min flow rate and 30°C. The developed method separates all 13 analytes within a 15 min run time with fewer experiments compared to the traditional quality‐by‐testing approach.     

Stability‐indicating HPLC assay for lysine–proline–valine (KPV) in aqueous solutions and skin homogenates

A simple, sensitive and stability‐indicating high‐performance liquid chromatographic (HPLC) assay method was developed and validated for a bioactive peptide, lysine–proline–valine (KPV) in aqueous solutions and skin homogenates. Chromatographic separation was achieved on a reversed phase Phenomenex C₁₈ column (4.6 × 250 mm, packed with 5 µm silica particles) with a gradient mobile phase consisting of 0.1% trifluoroacetic acid (TFA) in water (A) and 0.1% TFA in acetonitrile (B). The proposed HPLC method was validated with respect to accuracy, precision, linearity, repeatability, limit of detection (LOD) and limit of quantitation (LOQ). The calibration curve was linear with a correlation coefficient (r) of 0.9999. Relative standard deviation values of accuracy and precision experiments were <2. The LOD and LOQ of KPV were 0.01 and 0.25 µg/mL, respectively. Under stress conditions (acid, alkali and hydrogen peroxide) KPV yielded lys–pro–diketopiperazine as major degradation product, which was identified by flow injection MS analysis. The developed HPLC method was found to be efficient in separating the active peptide from its degradation products generated under various stress conditions. Also, the validated method was able to separate KPV from other peaks arising from endogenous components of the skin homogenate. Copyright © 2014 John Wiley & Sons, Ltd.     

Study of alternating current conduction mechanism in polypyrrole-magnesium ferrite hybrid nanocomposite through correlated barrier hopping model

In the present work, both polypyrrole (PPy) and optimized polypyrrole–magnesium ferrite (PPy-MgFe₂O₄) hybrid nanocomposite were synthesized separately by simple oxidative chemical polymerization method and then structurally characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The FTIR spectrum of the composite showed the presence of characteristic absorption bands of both PPy and MgFe₂O₄ in the composite confirming interfacial interaction of PPy with MgFe₂O₄. That this interaction is not affected by crystalline behaviour of predominant MgFe₂O₄ particles but that MgFe₂O₄ has embedded in PPy matrix was confirmed by XRD studies. Agglomerated granular spherical morphology of the composite was confirmed by SEM studies. Decrease in AC conductivity of the composite as compared to PPy due to the formation of interfacial heterojunction barrier between p-type PPy and n-type MgFe₂O₄ was confirmed experimentally and well supported theoretically by calculating binding energy, hopping distance and density of states at Fermi level of PPy and the composite as per CBH model.     

Detection of computer generated gravitational waves in numerical cosmologies

We propose to study the behavior of complicated numerical solutions to Einstein's equations for generic cosmologies by following the geodesic motion of a swarm of test particles. As an example, we consider a cylinder of test particles initially at rest in the plane symmetric Gowdy universe onT ³×R. For a circle of test particles in the symmetry plane, the geodesic equations predict evolution of the circle into distortions and rotations of an ellipse as well as motion perpendicular to the plane. The evolutionary sequence of ellipses depends on the initial position of the circle of particles. We display snapshots of the evolution of the cylinder.     

Solvent dynamics in a model system

We report herein a study of the solvent reorganization process in an electron transfer reaction. The calculations are based on a model consisting of 26 or 62 solvent particles. Molecular dynamics simulations are performed to calculate the electric field fluctuations during the orientational and translational motion of the solvent molecules. The changes in the electric fields at various points near the reacting sites in the system are evaluated as a function of time. From these electric fields, electric field time correlation functions are calculated. The main conclusion in this work is that it requires nearly 3 ps for the model solvent to reorient during the charge transfer. These results suggest ways of incorporating solvent dynamics based on molecular models into theoretical studies of electron transfer rates in condensed media.     

Incorporations of gold,silver and carbon nanomaterials to kombucha-derived bacterial cellulose: Development of antibacterial leather-like materials

Bacterial cellulose (BC), derived from kombucha scoby have extraordinary organoleptic properties suitable for development of leather-like materials. An improvement in physical and mechanical property is desirable for the practical applications. This work deals with the treatment of BC by incorporations of three different nanomaterials such as gold nanoparticles (AuNP), silver nanoparticles (AgNP) and graphene oxide (GO). Achieving combined benefits via synergic interactions of different nanomaterials is the major objective herein. While graphene oxide can influence some of the parameters related to mechanical properties, silver nanomaterials can offer antibacterial characteristics. Gold nano materials can bridge the BC/silver/graphene oxide as well as provide the desirable aesthetic colour. Different physical chemical and mechanical characteristics were studied in detail. For example, changes in morphology by imaging fiber network were studied using scanning electron microscopy. Fibre properties were studied by Small Angle X-Ray Scattering (SAXS) and X-Ray Diffraction (XRD). Elemental composition was studied by X-ray photoelectron spectroscopy (XPS) analysis and Raman analysis. The improvement of hydrophobicity was studied by Contact angle meter. Thermal analysis was performed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A Picture was provided in ESI to show the modified material's leather-like appearances.     

Spectrophotometric determination of clozapine in pharmaceuticals

New Spectrophotometric methods for the assay of clozapine (CZP) in pure and dosage forms are described. Method A is based on the oxidative coupling reaction of CZP with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ceric ammonium sulphate to form a coloured species (_max 570 nm). Method B is also based on the oxidative coupling reaction of CZP withP-,N,N-dimethylpheny-lenediamine dihydrochloride (DMPD) in the presence of sodium hypochlorite to form a coloured species (_max 690 nm). Method C is based on the formation of coloured charge-transfer complex between CZP and chloranilic acid (_max 540 nm). Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 2–25, 10–120 and 15–300 g/ml for methods A, B and C, respectively. The validity of the proposed methods was tested by analysing pharmaceutical dosage forms containing CZP and the relative standard deviation values were within 1.0%.     

A new sesquiterpene lactone from Bombax malabaricum

A new sesquiterpene lactone, 5-isopropyl-3-methyl-2,4,7-trimethoxy-8,1-naphthalene carbolactone (1) together with a known naphthoquinone, 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthoquinone (2) were isolated from the root bark of Bombax malabaricum. The structures of these two compounds were established by extensive one- and two-dimensional (1D- and 2D)-NMR spectral studies.     

Synthesis of fused triazolo-imidazole derivatives by sequential van Leusen/alkyne–azide cycloaddition reactions

A facile synthesis of fused triazolo imidazole derivatives by a van Leusen/alkyne–azide cycloaddition synthetic sequence is reported. The two-step reaction sequence generates compounds of significant molecular complexity from simple starting materials in an expedient fashion with good overall yields.