Aqueous Alkaline Medium Research Articles

Optimal preservation condition for the extraction of cell-free DNA from bile of patients with biliary tract cancer.

Patients with biliary tract cancer (BTC) often have dismal outcomes due to the poor performance of traditional methods for early diagnosis. Recently, bile cell-free DNA (cfDNA) has been reported as a potential liquid biopsy material for BTC diagnosis. However, bile is a complex alkaline aqueous medium, and the proper storage conditions for bile remain to be explored. The aim of this study is to explore the effects of storing bile under various conditions on the stability of bile cfDNA and to determine the optimal conditions, thereby establishing a foundation for the subsequent application of bile cfDNA in liquid biopsy for early diagnostic and prognosis monitoring of patients with malignant BTC. We evaluated the storage temperature and storage time for the preservation of bile samples. Bile samples were collected in cfDNA tubes with protectant covered inside or regular tubes without, and the stability of bile cfDNA was analyzed during 10 days at room temperature (RT) or after 2 months of storage at low temperatures. Bile cfDNA remained stable for bile samples being collected with cfDNA tubes and stored for 10 days at RT, while degraded with time for the case with regular tubes. When bile samples were collected with cfDNA tubes and stored for 2 months at 4 ℃, bile cfDNA remained stable, however, if collected with regular tubes, bile cfDNA exhibited a slight loss of integrity. No significant difference was observed for 2 months storage at -20 or -80 ℃. Our findings suggested that for bile cfDNA research, bile samples should be collected with cfDNA tubes and it can be transported for short-term shipment at RT, and could be stored at 4 ℃ with cfDNA tubes, or frozen at -20 ℃ with regular tubes.

Synthesis, enzyme inhibitory kinetics, & computational studies of N-(substituted phenyl)-(5-(3,4-dichlorobenzyl)-4-(4-chlorophenyl)-4H-1,2,4-triazol-3-ylthio)methylbenzamides: As potent alkaline phosphatase inhibitors

The present research work encompass an innovative approach towards the synthesis of potent series of target compounds (8a-j) having 1,2,4-triazole and benzamide moieties as alkaline phosphatase inhibitors. The synthetic methodology was initiated by Fischer's esterification of 3,4-dichlorophenylacetic acid (1) to achieve ethyl 2-(3,4-dichlorophenyl)acetate (2) which underwent hydrazinolysis using hydrazine hydrate under reflux to 2-(3,4-dichlorophenyl)acetohydrazide (3). The compound (3) with 4-chlorophenyl isothiocyanate (4) was base-catalyzed cyclization (10% aqueous NaOH) to 4-(4-chlorophenyl)-5-(3,4-dichlorobenzyl)-4H-1,2,4-triazole-3-thiol (5) under reflux via N-(4-chlorophenyl)-2-(2-(3,4-dichlorophenyl)acetyl)hydrazinecarbocarbothioamide, as an intermediate. Finally, a series of derivatives (8a-j) was synthesized by reacting (5) with different electrophiles; N-(aryl)-4-(chloromethyl)benzamides (7a-j) which were obtained by the reaction of substituted aryl amines (6a-j) with 4-(chloromethyl)benzoyl chloride in aqueous alkaline medium. The structural confirmation of all these novel derivatives was corroborated by contemporary spectral analysis i.e., IR, EI-MS, 1H and 13CNMR . The in vitro inhibitory potential of these benzamides against alkaline phosphatase enzyme disclosed that nine out of ten exhibited potent inhibition relative to standard used. Among these, 8i was identified as most potent molecule with IC50 value of (0.046 ± 0.013 μM), comparative to standard (5.241 ± 0.471 μM). The Kinetics mechanism examined by Lineweaver-Burk Plots (LBP), which revealed that 8i inhibited alkaline phosphatase enzyme competitively by forming an enzyme-inhibitor complex. The inhibition constant Ki determined from Dixon plots of this compound was 0.02 µM. The results of computational study were in full agreement with experimental proceedings and these ligands showed good interactions with the active site of enzyme. Based on the current investigations, these potent inhibitotrs might lead to further research gateways for the discovery of non-toxic medicinal scaffolds for dealing with the alkaline phosphatase ailments such as bone diseases and liver dysfunction. DFT analysis was also performed.

Zinc Extraction from Primary Lead Smelting Slags by Oxidant Alkaline Leaching

The purpose of this work is to obtain the optimum conditions for leaching the zinc contained in an industrial lead smelting slag. In this type of slag, zinc oxide, sulfide, and ferrite are contained. Zinc extraction from these compounds consists of using a single aqueous medium, where oxidant alkaline leaching with NaOH and NaClO was used. The parameters evaluated during the experiment were as follows: percentage of solids, NaOH/NaClO ratio, and temperature. The maximum amount of recovered Zn obtained during the leaching was 58%. This percentage was achieved by using the following optimal conditions: temperature of 60 °C, 0.22 of NaOH/NaClO ratio, 10% of solids, and a reaction time of 40 min. The calculated values of activation energy confirmed that the rate-limiting step of the reaction using the decreasing particle model is diffusion. The maximum percentage of zinc obtained could only have been achieved if the zinc oxide and part of the zinc sulfide (both present in almost equal proportions in the sample) were leached into the alkaline aqueous medium in the presence of NaClO.

Influence of anodic treatment of nickel in deep eutectic solvents on electrocatalytic activity in oxygen evolution and urea oxidation reactions

The influence of anodic potentiostatic treatment of nickel surface in deep eutectic solvents, ethaline and reline (eutectic mixtures of choline chloride with ethylene glycol and urea, respectively), on the electrocatalytic activity in the electrochemical reactions of oxygen evolution and urea oxidation in an aqueous alkaline medium (1 M NaOH) was investigated for the first time. It was shown that, depending on the chosen treatment potential and the nature of the eutectic solvent used, a significant increase in the rate of the studied processes was observed. Specifically, after anodic treatment of nickel under certain conditions, the polarization of the oxygen evolution reaction at a current density of 0.1 A/cm2 could be reduced by approximately 150–200 mV, and the maximum current density of urea oxidation could be increased by an order of magnitude (from 0.012 A/cm2 to 0.131 A/cm2 at a urea concentration of 0.33 mol/dm3 in alkaline solution). The observed increase in electrocatalytic activity after anodic treatment of nickel in deep eutectic solvents is likely related to changes in surface morphology patterns and the nature and concentration of relevant electroactive sites on the electrode surface. The results obtained in this work can be used for the development of highly efficient electrode materials for green hydrogen energy.

Degradable biporous polymeric networks based on 2-methylene-1,3-dioxepane: Towards hierarchically structured materials meant for biomedical applications

For the first time, the preparation of doubly porous “poly(ε-caprolactone)-like” networks through free-radical ring-opening copolymerization of 2-methylene-1,3-dioxepane with divinyl adipate was achieved via a double porogen templating approach. This versatile strategy allowed for the formation of macropores of around 150 μm generated by removal of sieved and sintered NaCl particles in water, while smaller pores in the 1–10 μm range were created by phase separation during the copolymerization process through a syneresis mechanism in the presence of a porogenic solvent. The chemical nature of the as-obtained scaffolds was evidenced by Raman spectroscopy. The two distinct porosity levels could be examined by scanning electron microscopy and mercury intrusion porosimetry. The nature of the porogenic solvent as well as its volume proportion and the amount of crosslinking agent in the polymerization feed allowed for finely tuning the porous features of the micropores. The crucial role of the double porosity of such biporous scaffolds on their water uptake and mechanical properties under compression was assessed by comparing them with their monoporous analogues, while their degradability was investigated in different alkaline aqueous media. The double porosity enabled a synergistic effect regarding the water uptake of the resulting scaffolds when compared to their monoporous counterparts. Doubly porous polymeric materials with appropriate mechanical properties were obtained, possessing high compressibility and shape memory behavior upon consecutive compression cycles. Finally, these materials display degradation rates that could be controlled depending on medium pH.

A Kinetic and Mechanistic Study of Ir (III)-Catalyzed Oxidation of Methionine by HCF (III) in an Aqueous Alkaline Medium

Introduction: The kinetic study of Ir (III) chloride-catalyzed oxidation of methionine by hexacyanoferrate (abbreviated as HCF) III ions in aqueous alkaline medium was performed spectrophotometrically at constant ionic strength of 0.5 moldm-3 and temperature of 35±0.10C. Method: The progress of the reaction was found to be first-order rate dependence kinetics with respect to [HCF (III)], [OH-], and [IrCl3]. The rate of reaction was found to decrease with an increased concentration of methionine. The ionic strength of the reaction mixture showed a positive salt effect on the reaction rate. Different activation parameters were also evaluated by studying the reaction at four different temperatures. The stoichiometry of the reaction showed Methionine: HCF (III) = 1:4. Result: The oxidation product of the reaction was found to be methionine sulphone, which was identified by an organic solvent method and IR Spectroscopy. Further, a suitable mechanism was proposed to explain all the experimental results. Conclusion: It is assumed that the reaction proceeded through complex formation between substrate (abbreviated) and iridium trichloride. A rate law was derived, which verified the results. CH3-S-(CH2)2-CH (NH2)-COO- + 4HCF (III) Ir (III), H2O CH3-SO2-(CH2)2-CH- (NH2)-COO- + 4HCF (II) result: 1.Methionine sulphone was found to be the main product of oxidation was identified using an organic solvent method and IR Spectroscopy. A suitable mechanism has been proposed to explain all the experimental results. It is assumed that reaction proceeds through complex formation between substrate (abbreviated) and iridium trichloride. A rate law has been derived which verifies the results. CH3 –S-(CH2)2-CH (NH2) – COO- + 4HCF (III) □(→┴(Ir(III),H2O) ) CH3-SO2-(CH2)2-CH (NH2)-COO- + 4HCF (II) 2. Degradation kinetic is anticipated to follow the first order kinetics at lower concentration. 3. The catalytic system can be recycled and reused without loss of activity. 4. The anticipated easy recovery of catalyst from the reaction mixture shows another positive signigficance.

Chemical compatibility between poly(ethylene) and cellulose nanofibers from kraft pulps containing varying amounts of lignin: An aqueous acetylation strategy and its effect on biocomposite properties

Previous efforts to acetylate fibers and cellulose nanofibers (CNFs) are methodologically demanding and usually based on organic solvents catalyzed by acids. Hence, the purpose of this study was to introduce an improved method to acetylate unbleached (2 % and 5 % lignin) and bleached fibers (<1% lignin), and the corresponding CNFs, using a one-pot strategy in an aqueous alkaline medium. The lignin content in the pulp fibers (5 %) influenced the morphology of the corresponding fibrillated materials, i.e., increased secondary fines (92 %) and mean fibril area (36 %). Additionally, the pulps and CNFs (0 % and 5 % lignin content) were acetylated and compounded with high-density poly(ethylene) (HDPE). Acetylation improved the mechanical strength from 19 MPa (HDPE) to 30–40 MPa (when including acetylated fibers or CNFs). Finally, acetylation revealed a positive effect on melt-flow-index and elongation at break, and the water absorption of injection molded specimens was reduced to roughly 0.6 % after 10 days of testing.

Kinetic perspectives for the degradation of oxacillin: A penicillanic acid derivative

Oxidation of oxacillin, a penicillanic acid derivative, has been predicted by monoperiodatocuprate [MPC (III)] at 25°C with 0.10 mol dm-3 ionic strength, in an aqueous alkaline medium by UV/Visible spectrophotometric analysis, for which 1:4 stoichiometry of oxacillin: MPC (III) is visible. The appearance of a sharp peak by the spectrophotometer confirmed the formation of the complex. The reaction products have been recognized using spectral reports from the FT-IR, LC-MS, melting point, and other spot tests. A pseudo-first-order reaction has been confirmed for the oxidant, fractional order for the substrate, and alkali, even though periodate claimed a delaying effect due to the accumulation of periodate ions from both potassium periodate and monoperiodatocuprate as a common ion effect. The primary active species in the alkaline medium [Cu(H2IO6)(H2O)2] was discovered to be monoperiodatocuprate [MPC (III)]. To figure out the activation and thermodynamic parameters, it is helpful to know the uncatalyzed rate constants, the slow step rate constants, and the equilibrium constants. We have evaluated the dependence of reaction rates on different temperatures. We have calculated rate constants using absorbance data collected from the UV/visible spectrophotometer. We have thoroughly examined the potential rate constant derivation and a plausible mechanism that could explain the experimental findings.

Tri‐Metallic Catalyst for Oxygen Evolution Reaction Enables Continuous Operation of Anion Exchange Membrane Electrolyzer at 1A cm−2 for Hundreds of Hours

AbstractAlthough numerous efforts are made to synthesize active electrocatalysts for green hydrogen production; catalyst stability, and facile synthesis to scale up the production are still challenging. Herein, the production of novel non‐PGM catalysts for the oxygen reduction reaction (OER) in an alkaline aqueous medium is reported, which is based on the synthesis of a trimetallic metal–organic framework (MOF) precursors. Fine‐tuning of the composition of the metal centers (Ni, Co, and Fe) shows a great effect on OER activity after the MOF undergoes dynamic chemical and structural transformations under OER conditions. In situ characterization reveals the origin of OER activity enhancement as metals’ oxidation state increases, inducing compressive mechanical strain on metal centers, enhancing the electronic conductivity through the formation of oxygen vacancies, and stronger metal–oxygen covalency. Catalysts are used in membrane electrode assembly (MEA) setup within an industrial full‐cell anion exchange membrane electrolyzer (AEMEC), showing a stable performance for 550 h without noticeable decay at 750 and 1000 mA cm−2 industrial level current densities.

Reactions of 1-amino-2-nitroguanidine with 3-nitroacrylates

The reactions of 1-amino-2-nitroguanidine with 3-nitro- acrylates afford aza-Michael adducts. The latter when refluxed in an aqueous alkaline medium undergo elimination of nitrous acid followed by shift of the resulting C=C bond into C=N position giving finally N-substituted alkylpyruvate hydrazones. These compounds can also be prepared in a one-pot procedure; NMR spectroscopy and X-ray diffraction analysis confirmed the existence of the obtained hydrazones as E-isomers.

A novel method for the remediation of o‐ and p‐aminophenol from industrial wastewater by hexacyanoferrate (III) ions using Ir‐complex catalyst

AbstractIn this manuscript o‐ and p‐aminophenols model environmental pollutants are being remedied by catalytic oxidation process. A kinetic‐spectrophotometric technique was used to study the remediation of o‐ and p‐aminophenol by hexacyanoferrate (III) ions as an oxidant and synthesized Ir‐DTPy complex as a catalyst in aqueous alkaline medium. The optimum pH for these experiments was 9.0 and 11.0 for o‐ and p‐aminophenol respectively at the constant temperature 25°C. It has been studied how variations in the concentration of the catalyst (Ir‐DTPy), the hexacyanoferrate (III) ions, and substrate affect the rate of the reaction. At four different temperatures, ranging from 25 to 40°C, the change in reaction rate has been analyzed with thermodynamic variables like free energy of activation, enthalpy, frequency factor, and activation energy. FTIR, UV‐Vis, and ESI‐MS spectroscopic analytical methods have been used to identify the oxidized products. 2‐aminophenoxazin‐3‐one and NN'‐bis‐(p‐hydroxyphenyl)‐2‐hydroxy‐5‐amino‐1, 4‐benzoquinone di‐imine are the main products of oxidation of o‐and p‐aminophenol, respectively. Therefore, this technique for removing o‐ and p‐aminophenol from contaminated water resources is very effective and environmentally safe.

A kinetic and mechanistic investigation of oxidation of D-Mannitol by Diperiodatocuprate (III) in an aqueous alkaline medium

A kinetic and mechanistic investigation of oxidation of D-Mannitol by Diperiodatocuprate (III) in an aqueous alkaline medium

Isolation of partial coupled processes of anodic oxidation of OH– ion on gold using a combination of a graph-kinetic analysis method and linear voltammetry data

The presence of several interconnected electrochemical processes occurring on the surface of an electrode, strictly speaking, does not allow the use of the principle of independent reactions. Often, partial reactions of a complex multi-stage electrochemical process are coupled both through common intermediates and through the competitive adsorption of electroactive species. The presence of conjugation leads either to a change in the potential at which the corresponding electrochemical process becomes possible or to a change in the rate of partial processes. The latter is called kinetic coupling. This does not allow the simple calculation of the rate of each partial reaction as the difference between the current density of the target and background processes. The method of kinetic diagrams can be used to establish the kinetic patterns ofsuch processes. This study shows that this method is applicable not only for the analysis of coupled electrochemical processes of various types, but can also be used in obtaining partial currents of the stages of a separate complex electrode reaction occurring in a background solution. As an example, options for the kinetic modelling of the total voltammogram of the anodic process on an Au electrode in an aqueous alkaline medium in the mode of linear potential change are considered. The stationary degrees of covering of the gold surface with various surface-active forms of oxygen are calculated depending on the electrode potential. It was established that the change in concentration of ОН- ions mainly affects the region of their adsorption potentials. A detailed analysis of stationary partial anodic processes in the Au|OH-,H2O system was carried out and the shape of the general stationary voltammogram was determined by calculation. The latter is in qualitative agreement with the experimental polarization dependence. It was shown that the type of calculated polarization dependence is determined by the degree of reversibility of individual stages and the rate of their occurrence. The performed analysis is necessary not only for the detailed scheme of the background anodic reaction on gold in an alkaline solution, but also for the ubsequent kinetic description of the electrooxidation process of organic substances on a gold electrode

Methylation of softwood and hardwood kraft lignins with chloromethane.

Methylation is a well-established means of enhancing the thermal stability, improving the compatibility in polymer blends, and lowering the glass-transition temperature of lignins. This process normally involves reagents that are costly, associated with poor atom economy and/or highly toxic. Herein, we report the methylation of softwood and hardwood kraft lignins using chloromethane in alkaline aqueous media. This reaction proceeds in high yields at 90-110 °C under moderate pressure (40 psi) while generating environmentally benign sodium chloride and water as by-products.

A molecular-design approach for selective sulfate separation from competitive acidic and alkaline aqueous media

The review encompasses an in-depth understanding of the choice of suitable anion receptors for recognition-guided selective sulfate separation from acidic and alkaline aqueous solutions containing several other competing ions.

Label-Free Detection of Unbound Bilirubin and Nitrophenol Explosives in Water by a Mechanosynthesized Dual Functional Zinc Complex: Recognition of Picric Acid in Various Common Organic Media.

High levels of unconjugated bilirubin (UB) in serum lead to asymptomatic and neonatal jaundice and brain dysfunctions. Herein, we have reported the detection of UB at as low as 1 μM in an aqueous alkaline medium using a Zn(II) complex. The specificity of the complex has been validated by the HPLC in the concentration window 6-90 μM, which is rare. The sensory response of the probe at physiological pH against nitro explosives developed it as an instant-acting fluorosensor for picric acid (PA) and 2,4-dinitrophenol (2,4-DNP). Spectroscopic titration provided a binding constant of 4×105 M-1 with PA. The naked eye detection was found to be 15 μM. The solid-state photoluminescent nature of the complex enabled it for PA sensing in the solid phase. Interestingly, the probe remained fluorescent in various volatile and non-volatile organic solvents. As a result, it can also detect PA and 2,4-DNP in a wide range of common organic media. NMR studies revealed the coordination of PA, 2,4-DNP, and UB to the Zn(II) center of the probe, which is responsible for the observed quenching of the probe with the analytes.

The electrochemical reduction of hydrogen peroxide on a palladium-amorphous carbon composite in an alkaline medium

The study of hydrogen peroxide reduction in an alkaline aqueous medium on a composite of palladium particles dispersed in an amorphous carbon matrix (Pd@AC) was performed. Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray Powder Diffraction (XRD) were used to examine morphology, composition, and crystalline structure. The crystalline structure and size of palladium were analyzed using XRD. The reduction of hydrogen peroxide was studied through cyclic and square-wave voltammetry in an alkaline solution in the absence and presence of dissolved oxygen. The overall electrocatalytic effect of Pd@AC toward hydrogen peroxide reduction strongly depends on the presence of oxygen and the hydrogen peroxide disproportionation reaction in the three-phase system of amorphous carbon, palladium particles, and electrolyte solution.

Electrocatalytic hydrogenation of 5-hydroxymethyfurfural reactions promoted by CuZn catalysts

Electrochemical hydrogenation of 5-hydroxymethylfurfural (HMF) is a particularly important and environmentally friendly route to achieve sustainable high-value chemicals and biomass-based fuels. Herein, electrocatalytic hydrogenation (ECH) reaction of HMF using CuZn catalysts prepared by electrochemical deposition method was declared. The electrochemical hydrogenation of HMF to 5-methyfurfuryl alcohol (MFA) in alkaline aqueous medium has an excellent yield and faraday efficiency, with a maximum of 0.086 mmol cm−2 h−1, which has not been reported before. The selectivity and efficiency of ECH reaction were affected by electrolyte pH. The results indicated that electrocatalytic hydrogenation were not simply related to the type of electrode catalyst, but also sensitive to electrolytes, which can give important guidance for electrocatalytic hydrogenation of biomass-based platform molecules.

Reaction of diphenylphosphinal formic acid hydrazide with isothiocyanates

A new method was proposed for the preparation of diphenylphosphinylformic acid hydrazide based on the reaction of phosphine oxide and trimethylchlorosilane in the presence of a tertiary amine, followed by interaction with chloroformic acid ester and then hydrazine hydrate. The hydrazide moiety was modified into a thiosemicarbazide moiety by reacting diphenylphosphinylformic acid hydrazide with organic isothiocyanates. It was found that in an aqueous alkaline medium, thiosemicarbazides do not heterocyclize to 1,2,4-triazole-3-thiones, as expected. As a result of the rupture of the P-C bond, diphenylphosphinic acid and a 5-thioxo-1,2,4-triazolidin-3-one were formed.

Smartphone based colorimetric point-of-care sensor for abused drugs: case of baclofen determination in urine

As a GABA-β receptor agonist, the central muscle relaxant Baclofen (BAC) has a potential of abuse. Unfortunately, the sense of wellbeing and pleasure is obtained at very high BAC doses. This is associated with many life-threating or even fatal cases due to neurological and respiratory failures. Moreover, having narrow therapeutic index makes BAC a high-risk drug. This is potentiated in case of long-treatment regimen or off-label use in smoking and alcohol cessation protocols. Until now, there is no rapid diagnostic test available for BAC screening. Therefore; It is quite difficult to routinely monitor cases on BAC regimen. On the other hand, smartphone-based colorimetric point of care testing (POCT) is displacing conventional analytical approaches in the detection and assay of abused drugs as well as therapeutic drug monitoring. It offers on-site, rapid, easy, affordable and interpretable analysis. Incorporating smartphone as a portable device facilitates its application, especially in remote areas and low-income countries. For the first time, the current work presents a smartphone-based colorimetric POCT for BAC analysis in urine without interference from urine matrix. It depends on BAC reaction with naphthoquinone sulfonate (NQS) in highly alkaline aqueous medium. The developed color was captured in a customized photo box using smartphone camera. Then, intensity of the blue channel was measured by a software application “Color Analyzer”. All parameters were optimized with respect to the colorimetric reaction, photographing and smartphone-based analysis. All parameters were successfully investigated according to FDA guidelines for bioanalytical method validation. Also, all POCT criteria were considered as per WHO requirements. This method could determine BAC, linearly, from 0.02 to 0.21 mmol L−1 in urine. Moreover, LLOQ was lower than the expected BAC therapeutic concentrations in urine. The proposed method proved high reliability and suitability to analyze BAC in urine. This strongly recommends its routine application in screening BAC abusers and BAC therapeutic monitoring.Graphical