Solvent selection in ultrasonic-assisted emulsification microextraction: Comparison between high- and low-density solvents by means of novel type of extraction vessel

There are numerous published reports about dispersive liquid phase microextraction of the wide range of substances, however, till now no broadly accepted systematic and purpose oriented selection of extraction solvent has been proposed. Most works deal with the optimization of available solvents without adequate pre-consideration of properness. In this study, it is tried to compare the performances of low- and high-density solvents at the same conditions by means of novel type of extraction vessel with head and bottom conical shape. Extraction efficiencies of seven basic pharmaceutical compounds using eighteen common organic solvents were studied in this work. It was much easier to work with high-density solvents and they mostly showed better performances. This work shows that although exact predicting the performance of the solvents is multifaceted case but the pre-consideration of initial selection of solvents with attention to the physiochemical properties of the desired analytes is feasible and promising. Finally, the practicality of the method for extraction from urine and plasma samples was investigated.     

Supported N-propylsulfamic acid on magnetic nanoparticles used as recoverable and recyclable catalyst for the synthesis of 2, 3-dihydroquinazolin-4(1H)-ones in water

An efficient and eco-friendly method is reported for the synthesis of 2-substituted-2,3-dihydroquinazolin -4（1 H）-ones from direct cyclocondensation of anthranilamide with aldehydes and ketones using N-propylsulfamic acid supported onto magnetic Fe₃O₄ nanoparticles（MNPs-PSA） as a recoverable and recyclable nanocatalyst in good to excellent yields in water at 70℃.The catalyst was readily separated using an external magnet and reusable without significant loss of their catalytic efficiency.     

Silver(I)‐N‐heterocyclic carbene complexes of bis‐imidazol‐2‐ylidenes having different aromatic‐spacers: synthesis,crystal structure,and in vitro antimicrobial and anticancer studies

A series of Ag(I) complexes ( 6 , 7 , 8 , 9 ) derived from imidazol‐2‐ylidenes was synthesized by reacting Ag₂O with an o‐, m‐, p‐xylyl or 1,3,5‐triazine‐linked imidazolium salts ( 1 , 2 , 3 , 4 ) and then characterizing these using various spectro‐analytical techniques. Additionally, triazine‐linked bis‐imidazolium salt 5 was characterized using the single‐crystal X‐ray diffraction method. Complexes 6–9 were formed from the N‐heterocyclic carbene ligand precursors 1–3 as PF₆^‐ salts in good yields. Conversely, salt 5 does not form Ag(I) complex even under various reaction conditions. Using ampicillin as a standard, complexes 6–9 were tested against bacteria strains Escherichia coli and Staphylococcus aureus as Gram‐negative and Gram‐positive bacteria, respectively, showing potent antimicrobial activities against the tested bacteria even at minimum inhibition concentration and bacterial concentration levels. Furthermore, the potential anticancer activities of the reported complexes were evaluated against the human colorectal cancer (HCT 116) cell lines, using 5‐fluorouracil as a standard drug. The highest anticancer activities were observed for complex 8 with an IC₅₀ value of 3.4 μm , whereas the lowest was observed for complex 9 with an IC₅₀ value of 18.1 μm . Copyright © 2013 John Wiley & Sons, Ltd.     

ALANINE/CHLOROCHROMIC ACID/SILICA GEL: AN EFFICIENT AND SELECTIVE REAGENT FOR THE OXIDATION OF ORGANIC FUNCTIONAL GROUPS

Alanine/chlorochromic acid/silica gel is a new and selective reagent for the efficient oxidation of sulfides, thiols, oximes, and alcohols. Oxidation of sulfides is solvent dependent. In chloroform at room temperature sulfoxides are formed as the major products, while in carbon tetrachloride or under solvent-free conditions solfones are produced in good-to-excellent yields.     

Minimum Norm Solution to the Absolute Value Equation in the Convex Case

In this paper, we give an algorithm to compute the minimum norm solution to the absolute value equation (AVE) in a special case. We show that this solution can be obtained from theorems of the alternative and a useful characterization of solution sets of convex quadratic programs. By using an exterior penalty method, this problem can be reduced to an unconstrained minimization problem with once differentiable convex objective function. Also, we propose a quasi-Newton method for solving unconstrained optimization problem. Computational results show that convergence to high accuracy often occurs in just a few iterations.     

The effect of starvation periods on the performance of a two-liquid-phase mixed tank bioreactor for removal of n-hexane from air streams

In this research the effect of silicone oil as a heavy organic solvent on the performance of a mixed tank bioreactor was investigated. In the first stage of the experiments, the response of a two-liquid-phase mixed tank bioreactor to periods of n-hexane starvation was compared with that of a control bioreactor. In the control bioreactor, after 3?days of starvation, approximately six days were needed to reach the removal efficiency it had before starvation. This figure was only 10?h for the silicone oil-containing bioreactor. The results confirmed that inclusion of a heavy organic solvent can increase the elimination capacity of a bioreactor and to help sustain high elimination capacity after starvation periods. In the second stage of the experiments, the effect of the amount of silicone oil on the performance of the bioreactor was investigated. Increasing the amount of oil from 5 to 10% (v/v) increased the maximum elimination capacity from 106 to 117?g/m³?h.     

Novel and sensitive UPLC–MS/MS method for quantification of sofosbuvir in human plasma: application to a bioequivalence study

A novel and sensitive LC–MS/MS method was developed and validated for determination of sofosbuvir (SF) using eplerenone as an internal standard. The Xevo TQD LC–MS/MS was operated under the multiple‐reaction monitoring mode using electrospray ionization. Extraction with tert‐butyl methyl ether was used in sample preparation. The prepared samples were chromatographed on Acquity UPLC BEH C₁₈ (50 × 2.1 mm, 1.7 μm) column by pumping 0.1% formic acid and acetonitrile in an isocratic mode at a flow rate of 0.35 mL/min. Method validation was performed as per the US Food and Drug Administration guidelines and the standard curves were found to be linear in the range of 0.25–3500 ng/mL for SF. The intra‐ and inter‐day precision and accuracy results were within the acceptable limits. A very short run time of 1 min made it possible to analyze more than 500 human plasma samples per day. A very low quantification limit of SF allowed the applicability of the developed method for determination of SF in a bioequivalence study in human volunteers. Copyright © 2016 John Wiley & Sons, Ltd.