Application of Multivariate Calibration Techniques to Simultaneous Spectrophotometric Determination of Copper and Iron Using 1‐(2‐Pyridylazo)‐2‐naphthol in AOT Micellar Solution

Multivariate calibration models (PCR and PLS) were developed for simultaneous determination of Fe(III) and Cu(II) with 1‐(2‐pyridylazo)‐2‐naphthol and AOT as chromogenic reagent and micellizing agent, respectively. In the presence of AOT the spectrum of Fe(III)‐PAN complex was shifted to higher wavelength and the overlapping with Cu‐PAN spectrum decreased. It seems that this anionic surfactant enters the structure of the Fe‐PAN complex to cause a shift in the absorption spectrum of it. The parameters controlling behavior of the systems were investigated and optimum conditions were selected. Sixteen ternary mixtures were selected as the calibration set. To select the number of factors in PCR and PLS algorithms, a cross validation method, leaving out one sample at a time, was employed. The calibration models were validated with 8 synthetic mixtures containing the metal ions in different proportions that were randomly designed. The best calibration model was obtained by using PLS regression. The method was successfully applied to simultaneous determination of copper and iron in biological samples.     

A High Performance Route for the Synthesis of Dihydropyrrolo[1,2‐f]phenanthridine Scaffolds by using a One‐pot Four‐component Reaction

Synthesis of a series pyridine containing dihydropyrrolo core fused phenanthridines by a one‐pot four‐component reaction in an efficient route is reported. This report contains the reaction of pyridinecarbaldehydes, malononitrile, and phenanthridine in the presence of alkyl isocyanides.     

Variational approaches to p-Laplacian discrete problems of Kirchhoff-type

Critical point results for Kirchhoff-type discrete boundary value problems are exploited in order to prove that a suitable class possesses at least one solution under an asymptotical behaviour of the potential of the nonlinear term at zero, and also possesses infinitely many solutions under some hypotheses on the behaviour of the potential of the nonlinear term at infinity. Some recent results are extended and improved. Some examples are presented to demonstrate the applications of our main results.     

One-step in-syringe dispersive liquid–liquid microextraction and GC-FID determination of trace amounts of di(2-ethylhexyl) phthalate and its metabolite in human urine samples

Di(2-ethylhexyl) phthalate (DEHP) is used as plasticizer in polyvinylchloride (PVC) plastics. Its metabolites and the parent phthalates are considered toxic. As the DEHP plasticizers are not chemically bound to PVC, they can migrate, evaporate or be leached into indoor air and atmosphere, foodstuff, and other materials. We have reported a novel, easy and available analytical method for the determination of DEHP and its metabolite, mono(2-ethylhexyl) phthalate (MEHP) in human urine samples by the in-syringe dispersive liquid–liquid microextraction method coupled with gas chromatography with flame ionization detector. The limits of detection and precision (RSD) were 2.5 μg/L and 1.4% for DEHP and 1.1 μg/L and 3.0% for MEHP, respectively. This method could be utilized for routine monitoring of the trace DEHP and MEHP in urine of human exposure to plasticizers.     

Fabrication of novel solid-state supercapacitor using a Nafion polymer membrane with graphene oxide/multiwalled carbon nanotube/polyaniline

In the current work, the effect of aniline concentration on the polymerization process and supercapacitive behavior of graphene oxide/multiwalled carbon nanotubes/polyaniline (GMP) nanocomposites were studied. Based on the obtained results, GMP nanocomposite with 0.5 M aniline (GMP5) was selected as the optimum concentration in terms of high current density and high specific capacitance. Nafion-based ionic polymer-free metal composite (IPFMC) supercapacitor was fabricated for the GMP5 nanocomposite. Solid-state symmetric supercapacitor was made after spraying of GMP5 in. on both sides of Nafion membrane. The electrochemical properties were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD), and electrochemical impedance spectroscopy (EIS) techniques in 0.5 M Na₂SO₄.The specific capacitance of 383.25 F g^?1 (326 mF cm^?2) and 527.5 F g^?1 (42 mF cm^?2) was obtained for the GMP5 in solid-state supercapacitor and three-electrode cell at a scan rate of 10 mV s^?1, respectively. The maximum energy and power densities of 53.64 and 1777.4 W kg^?1 were obtained for the IPFMC-based supercapacitor.

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Graphical abstract Schematic of the solid-state supercapacitor based on the GMP5 nanocomposite

     

A Remark on the Linearized Stability of Positive Solutions for Systems Involving the p-Laplacian

The aim of this paper is to prove some stability result for nonlinear elliptic systems of the form where Δ_p denotes the p-Laplacian operator defined by Δ_pz = div(|∇ z|^p-2∇ z); p > 2, Ω is a bounded domain in R^N (N > 1) with smooth boundary where with h = 1 when α = 1, λ is a positive parameter and f,g are C² functin on [0,∞) × [0,∞). We prove stability and instability results of positive stationary solutions under various choices of f and g.     

Efficient solvent-free synthesis of pyridopyrazine and quinoxaline derivatives using copper-DiAmSar complex anchored on SBA-15 as a reusable catalyst

A catalytic system comprising mesoporous silica functionalized with Cu(II)-DiAmSar was synthe-sized. This was demonstrated as an efficient heterogeneous catalyst for the synthesis of biologically useful pyridopyrazine and quinoxaline heterocycles under solvent-free conditions. X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, Fourtier transformation infrared spectroscopy, and thermogravimetric analysis were used to characterize the catalyst and investi-gate the texture of SBA-15 during the grafting process.     

Electrocatalytic determination of chlorpromazine drug using Alizarin Red S as a mediator on the glassy carbon electrode

The anodic oxidation of chlorpromazine (CPZ) has been studied on a glassy carbon electrode by electrocatalytic effect of Alizarin Red S (ARS) as a homogenous mediator in universal buffer (pH = 2). The linear sweep voltammetry (LSV) studies showed that the catalytic current of this system depends on the concentration of CPZ. The magnitude of the peak current for ARS increased severely in the presence of CPZ, and proportional to CPZ concentration. The catalytic peak current was linearly dependent on CPZ concentration in the ranges of 10–500 μM and the detection limit was 5.16 μM by LSV. The diffusion coefficient of CPZ was estimated using chronoamperometry. The method also was used for estimation of catalytic rate constant at catalytic reaction between ARS and CPZ. The influences of potentially interfering substances on the current response of the system were examined. The importance of technique is because of its ability to electrocatalytic determination of CPZ with ARS as homogenous electrocatalyst, while it does not need to be prepared as for the modified electrode. The method was successfully applied for analysis of CPZ in solid pharmaceutical formulations.     

UV-prepared salep-based nanoporous hydrogel for controlled release of tetracycline hydrochloride in colon

A highly swelling nanoporous hydrogel (NPH) was synthesized via UV-irradiation graft copolymerization of acrylic acid (AA) onto salep backbone and its application as a carrier matrix for colonic delivery of tetracycline hydrochloride (TH) was investigated. Optimized synthesis of the hydrogel was performed by the classic method. The swelling behavior of optimum hydrogel was measured in different media. The hydrogel formation was confirmed by Fourier transform infrared spectroscopy (FTIR) and thermo-gravimetric analysis (TGA/DTG/DTA). The study of the surface morphology of hydrogels using SEM showed a nanoporous (average pore size: about 350nm) structure for the sample obtained under optimized conditions. The drug delivery results demonstrated that this NPH could successfully deliver a drug to the colon without losing the drug in the stomach, and could be a good candidate as an orally administrated drug delivery system.     

Rapid and Highly Sensitive Detection of Target DNA Related to COVID-19 Virus With a Fluorescent Bio-conjugated Probe via a FRET Mechanism

Journal of Fluorescence - A novel cyanine 3 (Cy3)-based bio-conjugated sensor has been developed to detect target DNA or extracted RNA from COVID -19 samples using the fluorescence resonance energy...