Electrospun PDA‐CA Nanofibers toward Hydrophobic Coatings

Nowadays, encapsulated dyes in a polymeric matrix have opened up new perspectives in many applications such as filtration of subatomic particles, composite reinforcement, multifunctional membranes, tissue engineering scaffolds, wound dressing, coatings, medical purposes as well as sensors. In the presented work, we report on electrospinning neat peryelene dianhydride based thermoplastic elastomers. Perylene‐3, 4,9, 10‐tetracarboxylic dianhydride (PDA) is encapsulated into cellulose acetate (CA) electrospun fibers, which was prepared from 12 % cellulose acetate solution, at 20 kV with a distance of 10 cm. The flow rate was 0.2 ml · h^–1. These water repellent nanofibrous coatings are anticipated to serve as hydrophobic coatings. Scanning electron microscope is used to study the properties of the electrospun PDA‐CA nanofibers.     

Stability-indicating methods for determination of tiapride in pure form, pharmaceutical preparation, and human plasma

Four different stability-indicating procedures are described for determination of tiapride in pure form, dosage form, and human plasma. Second derivative (D2), first derivative of ratio spectra (1DD), spectrofluorimetric, and high-performance column liquid chromatographic (LC) methods are proposed for determination of tiapride in presence of its acid-induced degradation products, namely 2-methoxy-5-(methylsulfonyl) benzoic acid and 2-diethylaminoethylamine. These approaches were successfully applied to quantify tiapride using the information included in the absorption, excitation, and emission spectra of the appropriate solutions. In the D2 method, Beer's law was obeyed in the concentration range of 1.5-9 microg/mL with a mean recovery of 99.94 +/- 1.38% at 253.4 nm using absolute ethanol as a solvent. In 1DD, which is based on the simultaneous use of the first derivative of ratio spectra and measurement at 245 nm in absolute ethanolic solution, Beer's law was obeyed over a concentration range of 1.5-9 microg/mL with mean recovery 99.64 +/- 1.08%. The spectrofluorimetric method is based on the determination of tiapride native fluorescence at 339 nm emission wavelength and 230 nm excitation wavelength using water-methanol (8 + 2, v/v). The calibration curve was linear over the range of 0.2-3 microg/mL with mean recovery of 99.66 +/- 1.46%. This method was also applied for determination of tiapride in human plasma. A reversed-phase LC method performed at ambient temperature was validated for determination of tiapride using methanol-deionized water-triethylamine (107 + 93 + 0.16, v/v/v) as the mobile phase. Sulpiride was used as an internal standard at a flow rate of 1 mL/min with ultraviolet detection at 214 nm. A linear relation was obtained over a concentration range of 2-30 microg/mL with mean recovery of 99.66 +/- 0.9%. Results were statistically analyzed and compared with those obtained by applying the reference method. They proved both accuracy and precision.     

Development of an Innovative Nitrite Sensing Platform Based on the Construction of an Electrochemical Composite Sensor of Polymer Coated CNTs and Decorated with Magnetite Nanoparticles

Electrochemical determination of nitrite in real water samples is achieved using simple and efficient electrochemical sensor. The sensor is fabricated by electrodeposition of a thin layer of poly(3,4-ethylenedioxythiophene) sandwiched by drop-casting two thin layers of CNTs and iron oxide nanoparticles (Fe₃O₄) over a GC electrode surface. Voltammetry determination of nitrite in tap water and wastewater samples in the concentration range (0.5–150 μM) is successfully achieved with detection limits of 22 and 24 nM, respectively. Practical application of the GC/CNT/PEDOT/Fe₃O₄ sensor is efficiently assessed in real water samples for nitrite determination with acceptable recoveries, excellent anti-interference ability and long-term stability.     

Liquid Crystal Polymers: Overview of Characteristics and Applications in Communication and Biomedical Technologies

Russian Journal of Applied Chemistry - Liquid crystals polymers (LCPs) are aromatic polymers with unique properties which enable their usage in various applications. LCPs are herein discussed, in...     

Effect of zeolite structure on the selective catalytic reduction of NO with ammonia over Mn-Fe supported on ZSM-5, BEA,MOR and FER

A series of catalysts based on Mn-Fe loaded zeolites was prepared by impregnation and their activity in the selective catalytic reduction of NO with ammonia (NH₃-SCR) was investigated. The highest catalytic conversion was recorded for MnFe-ZSM-5 (MnFe-Z), followed by MnFe-BEA (MnFe-B) and MnFe-MOR (MnFe-M), while MnFe-FER (MnFe-F) showed a very poor activity over the entire temperature range. In order to evidence a correlation between the structure and acidity of the zeolites and NO conversion, the prepared samples were characterized by various techniques (ICP-AES, N₂ physisorption at 77 K, XRD, ²⁷NMR, Raman, FTIR spectroscopy of adsorbed ammonia, H₂-TPR, DRS UV–Vis, EPR and XPS). The superior catalytic activity of MnFe-Z at low temperature is attributed to the abundance of Mn⁴⁺ concentration as revealed by XPS, the highest NH₃-L/NH₄⁺ ratio indicative of the contribution of metals in generating Lewis acidic centers as evidenced by IR-NH3, and the better reducibility of manganese and iron on ZSM-5 which increases the kinetics for red-ox cycles as confirmed in TPR analysis. Fe₃Mn₃O₈ mixed oxide phase is also detected by XRD and XPS and can be associated with the high reducibility of MnFe-Z which generates a high oxidation ability favoring NO to NO₂ oxidation. Raman spectroscopy was also used to confirm the existence of a strong synergy between metals and ZSM-5 support revealed by the shift in the signal position and the decrease in band intensities. The results showed that the zeolite framework and acidity generate catalysts with different textural and structural properties which influence the metal dispersion and speciation and hence influence the catalytic performances.

     

Mechanism of anti-inflammatory action of liquorice extract and glycyrrhizin

The antiradical activity, protective effect against lipid peroxidation of liposomal membrane, and inhibitory effect on whole blood reactive oxygen species (ROS) liberation of Glycyrrhiza glabra crude extract and glycyrrhizin, its major compound, were assessed. The liquorice extract showed significant activity in all the three assay systems used in a dose dependent manner. It displayed remarkable reactivity with free stable 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical, inhibitory efficacy in peroxidatively damaged unilamellar dioleoyl phosphatidylcholine (DOPC) liposomes, and inhibition of ROS chemiluminescence, generated by whole blood, induced by both receptor-bypassing stimuli (PMA) and receptor operating stimuli (Opz) in the ranking order of stimuli PMA> Opz. These activities may be attributed to phenolic antioxidants involving isoflavan derivatives, coumarins and chalcones. Nonetheless, triterpene saponin glycyrrhizin exhibited no efficacy in the system of DPPH reaction and peroxidation of liposomal membrane, and negligible inhibition of chemiluminescence generated by inflammatory cells. These results indicate that the mechanism of anti-inflammatory effect of glycyrrhizin most probably does not involve ROS and this major constituent is not responsible for the inhibition effects of liquorice extract on neutrophil functions.     

Poly(3,4-ethylene-dioxythiophene) electrode for the selective determination of dopamine in presence of sodium dodecyl sulfate

A novel biosensor using poly(3,4-ethylene dioxythiophene) (PEDOT) modified Pt electrode was developed for selective determination of dopamine (DA) in presence of high concentrations of ascorbic acid (AA) and uric acid (UA) with a maximum molar ratio of 1/1000, and 1/100 in the presence of sodium dodecyl sulfate (SDS). SDS forms a monolayer on PEDOT surface with a high density of negatively charged end directed outside the electrode. The electrochemical response of dopamine was improved by SDS due to the enhanced accumulation of protonated dopamine via electrostatic interactions. The common overlapped oxidation peaks of AA, UA and DA can be resolved by using SDS as the DA current signal increases while the corresponding signals for AA and UA are quenched. The use of SDS in the electrochemical determination of dopamine using linear sweep voltammetry at modified electrode PEDOT/Pt resulted in detecting dopamine at relatively lower concentrations. The DA concentration could be measured in the linear range of 0.5 to 25 μmol L^? 1 and 30 μmol L^? 1 to 0.1 mmol L^? 1 with correlation coefficients of 0.998 and 0.993 and detection limits 61 nmol L^? 1 and 86 nmol L^? 1, respectively. The validity of using this method in the determination of dopamine in human urine was also demonstrated.     

Direct and Simple Electrochemical Determination of Morphine at PEDOT Modified Pt Electrode

A simple and rapid method for morphine detection is described based on PEDOT electrode in the presence of SDS. The electrochemistry of morphine is investigated by CV, LSV and SWV. The effect of common interferences on the current response of morphine namely AA and UA is studied. The electrode is applied to the selective determination of morphine in urine samples in the linear ranges 0.3–8 µmol L^?1 and 10–60 µmol L^?1, with low detection limits of 50 and 68 nmol L^?1, respectively and recovery of 96.4 %. The application of PEDOT is realized in determination of morphine in tablets successfully.