High-throughput micro-solid phase extraction on 96-well plate using dodecyl methacrylate-ethylen glycol dimethacrylate monolithic copolymer

A novel high-throughput device based on 96-micro-solid phase extraction (96-μ-SPE) system was constructed for multiresidue determination of nine pesticides in aquatic samples. The extraction procedure was performed on a commercially available 96-well plate system. The extraction module consisted of 96 pieces of 1 cm × 3 cm of cylindrically shaped stainless steel meshes. The prepared meshes were fixed in a home-made polytetrafluoroethylene-based constructed ninety-six holes block for possible simultaneous immersion of meshes into the center of individual wells. Dodecyl methacrylate and ethylene glycol dimethacrylate was copolymerized as a monolithic polymer and placed in the cylindrically shaped stainless steel meshes as extracting medium. A volume of 1 mL of the aquatic sample was transferred into the 96-well plate and the 96-μ-SPE device was applied for the extraction of the selected pesticides. Subsequently, the extracted analytes were analyzed by gas chromatography–mass spectrometry. Influential parameters such as polymer synthesis conditions, sorbent-to-sorbent reproducibility, ionic strength and extraction time were optimized. Intra and inter-sorbent reproducibility on 96-μ-SPE device were evaluated and results revealed that extraction yields are rather similar. Limits of detection were below 4 μg L⁻¹ and the coefficient of determination was satisfactory (r² > 0.99) for all the studied analytes. The developed method was successfully applied to the extraction and determination of the selected pesticides in surface water samples.     

Synthesis of New Metal‐Free 1,4,8,11‐Tetraaza[14]annulene Derivatives Using 2‐Heteroaryl‐substituted Trimethinium Salts

The reaction of 2‐heteroaryl‐substituted trimethinium salts (A, B, and C) with aromatic 1,2‐diamines ( a , b , c , d , and e ) in acetonitrile/acetic acid leads to 6,13‐disubstituted 1,4,8,11‐tetraaza[14]annulene derivatives ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ). The UV–vis spectral behavior of these compounds was examined in acetonitrile. Elemental analysis, IR, ¹H‐NMR, ¹³C‐NMR, and mass spectra confirm the molecular structure of the newly synthesized compounds.     

Simple Synthesis of Highly Functionalized Ketenimines

The 1:1 reactive intermediate generated by the addition of alkyl isocyanides to dibenzoylacetylene or dialkyl acetylenedicarboxylates was trapped by fairly strong NH acids such as isatin, phthalimide, 4-nitroimidazole, or 2-benzoylimidazole to yield highly functionalized ketenimines.     

N-Hydroxyphthalimide-Catalyzed Oxidative Production of Phthalic Acids from Xylenes Using O2/HNO3 in an Ionic Liquid

A simple and mild process for oxidation of xylenes to phthalic acids using N-hydroxyphthalimide/O₂/HNO₃ in an ionic liquid, wherein the ionic liquid can be successfully recovered and reused, is described.     

Synthesis of nanocrystalline zinc manganese oxide by thermal decomposition of new dinuclear manganese(III) precursors

Nanocrystalline manganese-doped zinc oxide was synthesized by thermal decomposition of a zinc oxide sol with two new dinuclear manganese(III) complexes as precursor. Thermal analysis results indicated that the decomposition of manganese precursors occurred at 269 and 314 °C. X-ray structural analysis shows the presence of dimanganese core in the complexes and the binding of the ligands to the manganese(III) is through N₂O₂. The manganese-doped zinc oxide composite was characterized by means of X-ray diffraction, scanning electron microscopy, and UV–Vis spectroscopy. Structural properties of the composites elucidated that the manganese ions have substituted the zinc ions without changing the wurtzite structure of zinc oxide.     

Cyclodextrin Host‐Guest Recognition Approach for Simultaneous Quantification and Voltammetric Studies of Levodopa and Carbidopa in Pharmaceutical Products

An electrochemical sensor for simultaneous quantification of Levodopa (L‐dopa) and Carbidopa (C‐dopa) using a β‐cyclodextrin/poly(N‐acetylaniline) (β‐CD/PNAANI) modified carbon paste electrode has been developed. Preconcentrating effect of β‐CD as well as its different inclusion complex stability with L‐dopa and C‐dopa was used to construct an electrochemical sensor for quantification of these important analytes. The overlapping anodic peaks of L‐dopa and C‐dopa at 810 mV on bare carbon paste electrode resolved in two well‐defined voltammetric peaks at 450 and 880 mV vs. Ag/AgCl, respectively, with a drastic enhancement of the anodic peak currents. Under optimized conditions, linear calibration curves were obtained in the ranges of 0.5–117 µM and 1.6–210 µM with detection limits down to 0.2 and 0.8 µM for L‐dopa and C‐dopa, respectively. The proposed electrode was successfully applied for the determination of L‐dopa /C‐dopa in pharmaceutical formulations and the results were in close agreement with the labeled values.     

Optimization of Wall Material of Freeze-Dried High-Bioactive Microcapsules with Yellow Onion Rejects Using Simplex Centroid Mixture Design Approach Based on Whey Protein Isolate,Pectin, and Sodium Caseinate as Incorporated Variables

For the food sector, onion rejects are an appealing source of value-added byproducts. Bioactive compounds were recovered from yellow onion rejects using a pulse electric field process at 6000 v and 60 pulses. The onion extract was encapsulated with whey protein isolate (WPI), pectin (P), and sodium caseinate (SC) with a mass ratio of 1:5 (extract/wall material, w/w). A Simplex lattice with augmented axial points in the mixture design was applied for the optimization of wall material for the encapsulation of onion reject extract by freeze-drying (FD). The optimal wall materials were 47.6 g/100 g (SC), 10.0 g/100 g (P), and 42.4 g/100 g (WPI), with encapsulation yield (EY) of 85.1%, total phenolic content (TPC) of 48.7 mg gallic acid equivalent/g DW, total flavonoid content (TFC) of 92.0 mg quercetin equivalent/g DW, and DPPH capacity of 76.1%, respectively. The morphological properties of the optimal encapsulate demonstrated spherical particles with a rough surface. At optimal conditions, the minimum inhibitory concentration (MIC) of the extract (mean diameter of inhibition zone: 18.8 mm) was shown as antifungal activity against Aspergillus niger.     

Encapsulation of Vitamin B12 by Complex Coacervation of Whey Protein Concentrate–Pectin; Optimization and Characterization

Vitamin B₁₂ (VB₁₂) is one of the essential vitamins for the body, which is sensitive to light, heat, oxidizing agents, and acidic and alkaline substances. Therefore, the encapsulation of VB₁₂ can be one of the ways to protect it against processing and environmental conditions in food. In this work, the influence of pectin concentration (0.5–1% w/v), whey protein concentrate (WPC) level (4–8% w/v) and pH (3–9) on some properties of VB₁₂-loaded pectin–WPC complex carriers was investigated by response surface methodology (RSM). The findings showed that under optimum conditions (1:6.47, pectin:WPC and pH = 6.6), the encapsulation efficiency (EE), stability, viscosity, particle size and solubility of complex carriers were 80.71%, 85.38%, 39.58 mPa·s, 7.07 µm and 65.86%, respectively. Additionally, the formation of complex coacervate was confirmed by Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). In addition, it was revealed that the most important factor in VB₁₂ encapsulation was pH; at a pH < isoelectric point of WPC (pH = 3), in comparison with higher pH values (6 and 9), a stronger complex was formed between pectin and WPC, which led to an increase in EE, lightness parameter, particle size and water activity, as well as a decrease in the zeta-potential and porosity of complex carriers.     

A sensitive opto-fluidic biosensor based on plasmonic-graphene/black phosphorous configuration for detection of hemoglobin concentrations

Optical Review - In this paper, a sensitive Opto-fluidic biosensor for detection of Hemoglobin concentrations in blood samples is proposed and considered. The proposed system is based on the...