Development of a new fluorimetric bulk optode membrane based on 2,5-thiophenylbis(5-tert-butyl-1,3-benzexazole) for nickel(II) ions

A highly sensitive and selective fluorimetric optode membrane for the determination of ultra trace amounts of Ni²⁺ ions was prepared. The plasticized PVC-membrane incorporating potassium tetrakis(p-chlorophenyl)borate (KTpClPB) and 2,5-thiophenylbis(5-tert-butyl-1,3-benzexazole) (TTBB), as a highly fluorescent chromoionophore, displays a calibration response for Ni²⁺ ions over a wide concentration range of 1.0×10⁻³ to 1.0×10⁻⁸ M. It has a relatively fast response of <40 s. In addition to high stability and reproducibility, and relatively long working lifetime, the sensor possesses good selectivity for nickel ions over several common diverse ions. The fluorescence signal of the optode membrane can be easily recovered by immersion in EDTA solution. The optode was applied successfully to the determination of traces of Ni²⁺ ion in edible oil and a wastewater sample from nickel electroplating industries.     

Potential Mechanisms of Photodynamic Inactivation of Virus by Methylene BlueI. RNA–Protein Crosslinks and Other Oxidative Lesions in Qβ Bacteriophage

A spectrum of oxidative lesions was observed in a bacteriophage-based model system that is very sensitive to the photodynamic activity of selected dyes. When suspensions of the intact bacteriophage Qβ were exposed to methylene blue plus light (MB+L), inactivating events, or "hits" occurred that were oxygen-dependent and that were associated with the formation of several specific lesions: (1) carbonyl moieties on proteins, (2) 8-oxo-7,8-dihydroguanine (8-oxoGua), and (3) single-strand breaks (ssb) in the RNA genome and (4) RNA-protein crosslinks. Formation of carbonyl groups associated with protein in the Qβ phage preparation correlated positively with photoinactivation of the phage with increasing doses of either of the sensitizers MB or rose bengal. Strand breaks in the Qβ genomic RNA were observable at high MB concentrations but appeared not to be significant at the lower concentrations of MB, as full-length Qβ RNA was observable well beyond the 99% inactivation point in MB dosage. It was shown that the number of 8-oxoGua lesions were unlikely to be sufficient to account for the number of lethal events. Following exposure to MB+L, crosslink formation between Qβ RNA and protein was observed by virtue of the location of RNA at the interface of phenol-aqueous extractions of phage suspensions. A significant increase over background of RNA-protein complexes (including full-length Qβ RNA) was observed at the lowest concentration of MB tested (0.5 μ M ), which corresponded roughly to an average of 2 lethal hits per phage or approximately 13% survival compared to the zero MB control (100% survival). Due to its close correlation with Qβ inactivation and its expected lethality, RNA-protein crosslink formation may be important as an inactivating lesion in bacteriophage Qβ following MB+L exposure.     

A Facile Room Temperature Synthesis of Zinc Oxide Nanostructure and Its Influence on the Flame Retardancy of Poly Vinyl Alcohol

In this work, poly vinyl alcohol–ZnO nanocomposites were synthesized via two different in situ and ex-situ methods. In ex-situ, at first zinc oxide nanostructures were synthesized by one-step precipitation reaction between zinc acetate and sodium hydroxide. The effect of different surfactants such as poly vinyl pyrrolidone, poly vinyl alcohol and poly ethylene glycol on the morphology of ZnO nanostructures was investigated. Nanostructures were characterized by X-ray diffraction, scanning electron microscopy. The influence of ZnO nanostructures on the flame retardancy of the poly vinyl alcohol matrix was studied using underwriter laboratories UL-94 analysis.     

High Speed Video Camera and Electrical Signal Analyses of Arcs Behavior in a 3-Phase AC Arc Plasma Torch

A 3-phase AC plasma torch has been developed and aims at overcoming some limits of the classical DC torches in terms of efficiency, cost and reliability. However, the arc behavior in 3-phase plasma torch remains poorly explored. This paper is dedicated to the high speed video camera at 100,000 frames per second and electrical signal analyses of arcs behavior in a 3-phase AC arc plasma torch. First, a reference case at 150 A, in nitrogen as working gas, has been deeply analyzed. Afterwards, a parametric study based on current and inter-electrode gap has been carried out. Results show that only one arc can exist at a given time and arcs rotate by switching from a pair of electrodes to another one, following the maximal electrical gap potential. However, a particular “abnormal” arc behavior was sometimes observed. Indeed, the arc motion within the inter-electrode gap increases the heat exchange and stabilizes the 3-phase discharge whereas the system is unbalanced when the arc is in the periphery. The analysis highlights that the arc motion is strongly influenced by the electrode jet velocity and repulsive Lorentz forces. The parametric study shows that the current increases both jet velocity and arc discharge stability. Elsewhere, the increase of the inter-electrode gap can also stabilizes the electrical 3-phase arc discharge. Furthermore, the correlation between arc motion and current waveform is highlighted. This work is likely to open the way toward a better understanding of 3-phase discharges in the perspective of their further optimization.     

Analysis of tamoxifen and its main metabolites in plasma samples of breast cancer survivor female athletes: Multivariate and chemometric optimization

A sensitive method based on liquid chromatography combined with a diode array detector was developed and validated to simultaneously determine tamoxifen, and its active metabolites N-desmethyltamoxifen, 4-hydroxytamoxifen, and endoxifen in human plasma samples. The green and sustainable vortex-assisted dispersive liquid-phase microextraction technique based on the natural hydrophobic deep eutectic solvent was used for the extraction and preconcentration of the analytes. Chemometrics and multivariate analysis were used to optimize the independent variables including the type and volume of deep eutectic solvent, extraction time, and ionic strength. Under optimal conditions, calibration curves were linear in a suitable range with the lower limits of quantification (0.8–10.0 μg/L), which covered the relevant concentrations of the analytes in plasma samples for a clinical study. Intra- and interday precision evaluated at three concentrations for the analytes were lower than 8.2 and 12.1%, respectively. Accuracy was in the range of 94.9–104.7%. The applicability of the developed method on human plasma samples illustrated the range 45.1–72.8, 98.4–128.3, 0.9–1.2, and 2.7–6.1 μg/L for tamoxifen, N-desmethyltamoxifen, 4-hydroxytamoxifen, and endoxifen, respectively. The validated method can be effective for the pharmacokinetics, pharmacodynamics, and therapeutic drug monitoring studies of tamoxifen and its main metabolites in biological fluids.     

Highly functionalized pyrazolines from symmetric and asymmetric 1,2-disulfonylhydrazines: a combination of experimental and DFT perspectives

Chemistry of Heterocyclic Compounds - In this work, new pyrazole derivatives were prepared by one-pot three-component reaction emloying symmetric and asymmetric 1,2-disulfonyl-hydrazines,...     

A comparison on efficiency of virgin and sulfurized agro-based adsorbents for mercury removal from aqueous systems

Mercury adsorption by sulfur impregnated adsorbents seems to be one of the most efficient ways for removal of this toxic metal ion from wastewater and atmosphere. The aim of this work was to develop a method for preparation of low-cost sulfurized adsorbent from agricultural wastes; this approach combines two stages of (i) chemical activation with phosphoric acid and (ii) impregnation with powdered sulfur, in one step only. The physico-chemical properties of sulfurized adsorbent (AC-S) were determined with BET, FT-IR, Eschka method and pH_PZC measurements, and compared with those of the virgin sample (AC). It was found that sulfurization according to this method can introduce about 8 wt.% sulfur into the structure of adsorbent, in the forms of C–S, S–H, S–S and S=O functional groups. Although during the sulfur introduction processes, a decrease in surface area and micropore volume of the sulfurized adsorbent is to be expected, not only such decrease did not occur in this work, but a large increase in microporosity was seen. Thereupon, both the sulfur functionalities and extended microporosity of AC-S lead to higher capability of this sample for mercury adsorption rather than AC. Finally, the kinetics and equilibrium of mercury adsorption from aqueous solutions were studied for AC and AC-S.     

Synthesis of dialkyl 5-(aryl)-1-phenyl-1H-prazole-3,4-dicarboxylates via a one-pot and four-component reaction

A number of new dialkyl 5-(aryl)-1-phenyl-1H-prazole-3,4-dicarboxylate derivatives have been prepared regiospecifically in moderate to good yield from the cyclocondensation reaction of dialkyl (E)-2-(dialkoxyphosphoryl)-3-(aroyl)-2-butenedioate, derived from the reaction between trimethyl phosphite, an acetylenic ester, and an aroyl chloride, with phenylhydrazine. The reaction is four-component and is carried out under reflux conditions in dry toluene.     

Separation/preconcentration and determination of vanadium with dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and electrothermal atomic absorption spectrometry

A novel dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) for separation/preconcentration of ultra trace amount of vanadium and its determination with the electrothermal atomic absorption spectrometry (ETAAS) was developed. The DLLME-SFO behavior of vanadium (V) using N-benzoyl-N-phenylhydroxylamine (BPHA) as complexing agent was systematically investigated. The factors influencing the complex formation and extraction by DLLME-SFO method were optimized. Under the optimized conditions: 100 μL, 200 μL and 25 mL of extraction solvent (1-undecanol), disperser solvent (acetone) and sample volume, respectively, an enrichment factor of 184, a detection limit (based on 3S_b/m) of 7 ng L⁻¹ and a relative standard deviation of 4.6% (at 500 ng L⁻¹) were obtained. The calibration graph using the preconcentration system for vanadium was linear from 20 to 1000 ng L⁻¹ with a correlation coefficient of 0.9996. The method was successfully applied for the determination of vanadium in water and parsley.