A new, efficient, and simple method for the synthesis of thiiranes from epoxides under solvent-free conditions

A simple, efficient, and new method has been developed for the synthesis of thiiranes from epoxides through a one-pot reaction of epoxides with diethyl phosphite in the presence of ammonium acetate or ammonium hydrogen carbonate/sulfur/ and acidic alumina under solvent-free conditions using microwave irradiation.     

Electrochemical platform for simultaneous determination of levodopa,acetaminophen and tyrosine using a graphene and ferrocene modified carbon paste electrode

Microchimica Acta - A carbon paste electrode (CPE) was modified with graphene and ethyl 2-(4-ferrocenyl-[1,2,3]triazol-1-yl) acetate (EFTA) and used for electrocatalytic oxidation of levodopa....     

Inside-Needle Extraction Method Based on Molecularly Imprinted Polymer for Solid-Phase Dynamic Extraction and Preconcentration of Triazine Herbicides Followed by GC–FID Determination

An inside-needle extraction method was developed through thermal polymerization of atrazine-molecularly imprinted polymer (MIP) on the internal surface of a stainless steel hollow needle, which was oxidized and silylated. The fabricated coating (MIP layer) for the needle was durable and showed very good chemical and thermal stability. It could be mounted on a glass syringe and be directly coupled with gas chromatographic (GC) systems. The parameters being effective on the coating and extraction processes, namely nature of oxidizing agent, silylation time, nature and amount of porogen, template-to-MIP components ratio, polymerization time and temperature, sample volume, flow rate, pH and ionic strength of the sample were investigated and optimized. The extraction needle showed high selectivity as well as a great extraction capacity for triazines. The extraction of atrazine, simazine, cyanazine, ametryn, prometryn and terbutryn using the fabricated extraction needle and followed by GC analysis resulted in detection limits of 2.6, 21, 24, 32, 38 and 42 ng mL⁻¹, respectively. The fabricated needle proved to be applicable to the analysis of real samples by comparing the results obtained for non-spiked and spiked samples of grape juice, tap water and groundwater.

     

CFD Simulation of Rheological Model Effect on Cuttings Transport

Foam, as a non-Newtonian fluid, plays an important role in the underbalanced drilling technique in oil field development. The rheological properties of drilling fluids, such as foam, have a direct effect on flow characteristics and hydraulic performance. Two rheological models—the Herschel–Bulkley model and power law—were fitted to two foam systems in this study. Computational fluid dynamics (CFD) was used to simulate the effect of the rheological models on solid–liquid (cuttings transport) hydraulics in concentric and eccentric annulus during the foam drilling operation. The simulation results are compared to the experimental data from previous studies. The results of CFD using the power law model are in good agreement with experimental results in horizontal annulus with respect to the Herschel–Bulkley model with relative error less than 8%. Thus, for CFD cuttings transport for simulations in inclined and horizontal annulus, it is best to use the power law's rheological model parameters.     

Adsorption/desorption of acid violet-7 onto magnetic MnO2 prior to its quantification by UV–visible spectroscopy: optimized by fractional factorial design

Research on Chemical Intermediates - A highly efficient magnetic adsorbent is presented to preconcentrate acid violet-7 (AV-7) prior quantifying by UV–visible spectroscopy...     

Size‐Mediated Recurring Spinel Sub‐nanodomains in Li‐ and Mn‐Rich Layered Cathode Materials

Li‐ and Mn‐rich layered oxides are among the most promising cathode materials for Li‐ion batteries with high theoretical energy density. Its practical application is, however, hampered by the capacity and voltage fade after long cycling. Herein, a finite difference method for near‐edge structure (FDMNES) code was combined with in situ X‐ray absorption spectroscopy (XAS) and transmission electron microscopy/electron energy loss spectroscopy (TEM/EELS) to investigate the evolution of transition metals (TMs) in fresh and heavily cycled electrodes. Theoretical modeling reveals a recurring partially reversible LiMn₂O₄‐like sub‐nanodomain formation/dissolution process during each charge/discharge, which accumulates gradually and accounts for the Mn phase transition. From the modeling of spectra and maps of the valence state over large regions of the cathodes, it was found that the phase change is size‐dependent. After prolonged cycling, the TMs displayed different levels of inactivity.     

Numerical study of Phan-Thien–Tanner viscoelastic fluid flow around a two-dimensional circular cylinder at a low Reynolds number: a new classification for drag variations regimes

Meccanica - This study numerically investigates a low Reynolds two-dimensional flow of a viscoelastic fluid over a circular cylinder using the finite volume method. The Phan-Thien–Tanner...     

Voltammetric Ion‐Selective Nanocomposite Carbon Paste Electrode for Determination of Erbium at the Interface Between two Immiscible Electrolyte Solutions

In this study for the first time a novel erbium(III) voltammetric ion‐selective nanocomposite carbon‐paste electrode was introduced based on the concept of ion transfer at the interface between two immiscible electrolyte solutions. N′‐(2‐hydroxy‐1,2‐diphenylethylidene) benzohydrazide (HDB) was used as a selective ionophore in the composition of the carbon paste. The ionophore facilitates transfer of Er(III) from the aqueous solution to the room temperature ionic liquid (RTIL) phase after reduction of the redox probe to maintain charge neutrality. The plot of the peak potential versus the logarithm of the concentration exhibits a Nernstian response (19.9±0.2 mV decade^?1) toward Er(III) in the range of 7.5×10^?7–1.0×10^?1 mol L^?1 with detection limit of 5.0×10^?7 mol L^?1. The proposed sensor shows a fast response time of about 5 s.     

Sm3+ Potentiometric Membrane Sensor as a Probe for Determination of Some Pharmaceutics

The increase use of ion sensors in the fields of environmental, agricultural, and medical analysis is stimulating analytical chemists to develop new sensors for fast, accurate, reproducible, and selective determination of various ions. In this study a new samarium membrane sensor was constructed and for the first time, it was applied as a probe in indirect determination of hyoscine, homatropine, and tramadol drugs in their pharmaceutical formulation. The proposed membrane sensor was constructed based on a membrane containing 2% sodium tetraphenyl borate (NaTPB) as an anionic additive, 63% dibutyl phthalate (DBP) as solvent mediator, 5% ionophore, and 30% poly(vinyl chloride) (PVC). The proposed Sm(III) electrode exhibits a Nernstian response of 19.35±0.2 mV per decade of samarium concentration, and has a lower detection limit of 1.0×10^?7 M. The linear range of the sensors was 1.0×10^?7–1.0×10^?1 M. It works well in the pH range of 3.0–8.0.