Toluene System Research Articles

Smartphone based TLC approach versus conventional densitometric measurement for the simultaneous determination of donepezil and memantine, content uniformity testing along with greenness and whiteness assessment

Thin layer chromatography (TLC) is a straightforward and economical technique that plays a major role in analytical field. Introducing the amenities of smartphones as accessible alternative detectors to TLC separation methods elaborates the cost-effectiveness of this technique and supports the appropriate assay of various aliphatic compounds after visualization by suitable reagents. Herein, two TLC coupled with smartphone's camera approaches are proposed for the assay of donepezil hydrochloride (DON) and memantine hydrochloride (MEM), a combined medication used in the management of Alzheimer's disease. Separation was achieved using a developing system of ethyl acetate, methanol, toluene, and ammonia (33%, w/v) in a ratio of 4:1:4:0.2, by volume. The dried plates were scanned at 190 nm for the densitometric assay, then visualized with modified Dragendorff's reagent and photographed by smartphone's camera. The data were integrated by displaying the photos in either ImageJ software or Color-Picker application. The findings produced from the three detection approaches were contrasted over concentration ranges of 1–18 & 4–28 μg/spot for the densitometric method, while the range was 1–20 & 1–30 μg/spot for the ImageJ method and 3–18 & 2–20 μg/spot for the Color-Picker method for DON and MEM, respectively. The methods were suitable for assaying both drugs in their pure form and combined pharmaceutical formulations. Densitometric and ImageJ-based methods were applied to evaluate the dosage forms content uniformity. The developed methods were assessed by three metric tools for greenness and sustainability, namely Green Analytical Procedure Index, Analytical GREEnness Metric Approach, and White Analytical Chemistry.

Quality control and shelf-life study of Ayush CCT formulation

BACKGROUND: One of the most widely popular brews globally is green tea/black tea, prepared by steeping the leaves of Camellia sinensis (L.) Kuntze plant. The examination of shelf-life proves to be a crucial tool in Ayurvedic formulations, particularly for ensuring the prolonged durability of the finished products. METHODS: The formulation underwent shelf-life studies maintaining conditions at 30°C ± 2°C and 65% RH ± 5% RH. The shelf-life dynamics were scrutinized through withdrawals at 0 day and at 3-month intervals to maintain the efficacy over a period of 24 months. In the current research, notable alterations were not detected in diverse physical, chemical, and safety parameters studied for shelf-life assessment. These parameters include pH, loss on drying at 105°C, ash values, extractive values, microbial contamination, high-performance thin-layer chromatography (HPTLC) profile, thermal analysis, and aflatoxins, all evaluated at different intervals throughout the entire study period. RESULTS: The current research study comprises of HPTLC fingerprint profiling of C. sinensis leaf and formulation, employing the solvent system of toluene: ethyl acetate: formic acid (6.5:3.4:0.1) with caffeine as the reference standard and safety parameters along with total phenolic content (6.9379 %w/w) and total flavonoid content (3.31 %w/w). The quantitative estimation values of caffeine in Ayush CCT and in C. sinensis leaf were 0.83% and 2.44%, respectively. CONCLUSION: It can be inferred that the Ayush CCT formulation demonstrates a shelf-life of more than 2 years. The study encompassed the assessment of shelf-life, as well as the qualitative and quantitative estimation of caffeine as a bioactive constituent in Ayush CCT formulation and C. sinensis extract.

Modeling of microfluidic solvent extraction: Evaluation of different flow regimes and cascade configurations

ABSTRACT Solvent extraction using a microfluidic platform is one of the process intensification tools. It may involve different two-phase flow regimes that have different physical and mass transfer characteristics. Therefore, this study focuses on the selection of a better flow regime, flow conditions and cascade configuration (cross or counter-current) using mathematical modeling for a typical high-throughput application (1000 L/day). The mathematical model is based on a plug flow model. The liquid–liquid system considered is a water–acetone–toluene system. The different flow regimes such as slug flow (SF), slug-droplet flow (SDF) and core-annular flow (CAF) in different cascade configurations are compared on the basis of parameters like specific extraction rate (SER), solvent extraction process effectiveness (SEPE) and modified merit index (MMI). Among the different flow regimes and cases studied, CAF is found to offer lesser parallel paths, total extraction length, total pressure drop and residence time. The best case of CAF has higher SER (3.6 times), SEPE (3.6 times) and MMI (21.8 times) than the best case of SF in both cascades. SDF shows the results between SF and CAF. For a specific flow regime, higher values of parameters are obtained at higher flow rates. Counter-current cascade is found to be better than cross-current cascade.

Non-covalent self-assembly of substituted phthalocyanine with C60, C70, and 9-phenylanthracene: Spectroscopic insights and DFT calculations

Self-assembly of non-covalent donor-acceptor systems based on (octakis-3,5-di-tert-butylphenoxy)phthalocyanine (H2Pc(3,5-tBuPhO)8) and С60, С70 or 9-phenylanthracene (PhAn) is observed and described using the UV–vis and steady-state/time-resolved fluorescence methods. The 1:1 stoichiometry of the H2Pc(3,5-tBuPhO)8 - С60/С70/PhAn supramolecule was established by Job's method. The fluorescence quenching of phthalocyanine in the mentioned systems in toluene, indicating close bonding between a donor and an acceptor, was observed. The bonding constants are 1.2 × 104 M−1, 2.4 × 104 M−1, and 3.9 × 102 M−1 for the C60, C70, and PhAn derivatives, respectively. Using time-resolved fluorescence measurements, the static mechanism of quenching was established. The H2Pc(3,5-tBuPhO)8 fluorescence lifetimes in the absence and presence of С60/С70/PhAn, the charge separation rate constant (kCS) and the charge-separated state quantum yield (ΦCS) of donor-acceptor systems were calculated. (С70)H2Pc(3,5-tBuPhO)8 displays the highest kCS and ΦCS in good agreement with its stability parameter. Quantum-chemical calculations of the molecular spatial/electronic structure and the HOMO/LUMO composition that were revealed by DFT and TD DFT methods point to the H2Pc(3,5-tBuPhO)8 → fullerenes redistribution of the electron density and to the opposite one in the PhAn complex.

Study of Activation Energy for Viscous Flow of Mixtures as a Measure of Dilution Efficiency for Heavy Oil-Diluent Systems

As the demand for crude oil continues to increase in response to the continued global needs for it, the development of unconventional crude oil reserves is the only way to sustain global supply. However, the excessively higher viscosity of heavy crude oil makes it less attractive for conventional pipeline transportation. Therefore, reducing the viscosity of heavy crude oil to meet crude oil transporting pipeline regulations is a necessity. This paper has assessed the dilution efficiency of well-known diluents in the petroleum industry, using different dilution ratios based on a thermodynamic approach involving activation energy and heat of vaporization determination. Based on selected dilution ratios, kinematic viscosities of binary and ternary systems of toluene and natural gas condensate as diluents, and Saudi Heavy crude oil as the base oil were measured, using anticipated field based temperatures reported in the literature, which facilitated the experimental approach. The study shows that although the ternary systems have the lowest activation energy for viscous flow and heat of vaporization in accordance with the thermal activation theory of viscous flow, natural gas condensate binary systems have the lowest cost of transportation per barrel of total fluid in the transporting pipeline. The study further shows that the binary systems for toluene and Saudi Heavy crude oil have higher activation energy for viscous flowed compared to the toluene systems.

Selective Synthesis of Functionalized 3(2H)‐Furanones via Tandem Michael Addition/Rearrangement/Cyclization Reaction of Aliphatic Alkynones: A Combined Experimental and Theoretical Study

AbstractA novel catalyst‐ and solvent‐controlled dimerization of aliphatic alkynones through tandem Michael addition/rearrangement/cyclization sequence has been developed. The elaborated protocol provides a convenient chemo‐, regio‐ and stereoselective access to rare 3(2H)‐furanones decorated with 2‐exo‐methylene and 4‐ethenyl functionalities. A comprehensive density functional theory (DFT) study of possible reaction mechanism including ab initio molecular dynamics (AIMD) simulations and quantum theory of atoms in molecules (QTAIM) analysis of various substrate/catalyst/solvent complexes has revealed the Janus‐like behavior of the employed sodium tert‐butoxide/toluene system that is responsible both for the chemoselectivity of the initial addition step and the inhibition of the final cyclization step.

Synthesis of dioctyl sebacate catalysed by cellulose-immobilized lipase

Dioctyl sebacate is a long carbon chain dibasic acid ester with methylene as the main body. It is widely used in plasticizers because of its good cold resistance and high viscosity. And it has excellent properties of non-toxicity and easy biodegradation, so it can be used as a potential new green bio-based plasticizer. At present, most of the preparation methods of dioctyl sebacate are chemical methods, which have many by-products and cause environmental pollution. In this article, cellulose microspheres were used as a carrier to immobilize Candida antarctica lipase B (CALB) to catalyse the esterification of sebacic acid and n-octanol to prepare dioctyl sebacate. Through single factor experiments, the lipase immobilized on cellulose microspheres was optimized to determine the best process conditions: add 500 µL CALB to the erlenmeyer flask, and then add 0.02 mol/L PBS buffer (pH 8.0). After being prepared into a 5 mL system, 0.1 g of cellulose microspheres were added as a carrier and reacted for 3 h at 35 °C and 180 r/min. Added 0.5 vt% polyethylene glycol diglycidyl ether (PEGDEG) to the system for crosslinking. The final immobilization rate of lipase immobilized on cellulose microspheres was 80.06%, and the enzyme activity was 288.07 U/g. Using the cellulose-immobilized lipase as a catalyst, in the toluene system, the molar ratio of n (sebacic acid)/n (n-octanol) substrate was 1:3.5, the amount of immobilized enzyme was 0.04 g, 4 Å molecular sieve 1.5 g, 40 °C, and 150 r/min for 30 h, the conversion rate of dioctyl sebacate was 76.45%.

Effect of brine salinity on the partitioning, distribution and corrosion inhibition performance of a quaternary amine corrosion inhibitor

Surfactant corrosion inhibition performance in water–oil environments is influenced by complex relationships between their physical properties, solution chemistry and interfacial characteristics. The existence of polar heads/nonpolar tails influences both the preferential distribution of the surfactant between the two media as well as the phase in which micellisation occurs. Both phenomena affect the efficiency of the surfactant inhibitor and its adsorption at the metal-solution interface. To demonstrate the complexity of such interactions, the effect of brine salinity on the critical micelle concentration (CMC) and partitioning/distribution behaviour of a quaternary amine corrosion inhibitor (alkyldimethylbenzylhexadecylammonium chloride, or BAC-C16) in a brine and toluene system (at 1:1 ratio) was explored. All experiments were conducted at 50 °C and pH4 over varying salinities (0.1, 1 and 10 wt%) of NaCl brine. Both CMC and partitioning characteristics of BAC-C16 are significantly affected by aqueous phase salinity, with an inversion of the partitioning response observed between concentrations of 0.1 and 1 wt% NaCl. The effect of BAC-C16 partitioning/distribution behaviour on corrosion inhibitor performance was examined using rotating cylinder electrode experiments. The results illustrate that in order to establish the true corrosion inhibition behaviour, consideration of the chemical distribution characteristics is crucial.

Economic, environmental, exergy (3E) analysis and multi-objective genetic algorithm optimization of efficient and energy-saving separation of diethoxymethane/toluene/ethanol by extractive distillation with mixed extractants

Diethoxymethane, toluene, ethanol are important organic solvents with excellent performance and are widely used in the industrial fields. In this study, extractive distillation with mixed extractants was used to separate the mixture. The separation process of diethoxymethane, toluene and ethanol azeotrope system with different extractant agents was designed. The multi-objective optimization was carried out with the objective of total annual cost and gas emission, and the optimal process parameters were obtained by coordinating the two objectives. Based on the best extractive distillation process with mixed extractants, the intensification of process was performed by adding heat pump and heat integration technology, to improve the economy and energy consumption of the process. By comparing the results of economic, environmental and exergy efficiency analysis calculations, it was found that the intensification of the heat integration technology was better than the intensification of the heat pump. As for the intensification effect of heat integration technology saved about 5.5% more economical than primary mixed extractants process, the gas emission had been reduced by about 14.8% in terms of environment, and exergy loss decreased by 33.8%. This study provides theoretical guidance for the design and optimization of extractive distillation processes using the mixed extractants.

Synthesis and Characterization of ABA-Type Triblock Copolymers Using Novel Bifunctional PS, PMMA, and PCL Macroinitiators Bearing p-xylene-bis(2-mercaptoethyloxy) Core.

Syntheses of novel bifunctional poly(methyl methacrylate) (PMMA)-, poly(styrene) (PS)-, and (poly ε-caprolactone) (PCL)-based atom transfer radical polymerization (ATRP) macroinitiators derived from p-xylene-bis(1-hydroxy-3-thia-propanoloxy) core were carried out to obtain ABA-type block copolymers. Firstly, a novel bifunctional ATRP initiator, 1,4-phenylenebis(methylene-thioethane-2,1-diyl)bis(2-bromo-2-methylpropanoat) (PXTBR), synthesized the reaction of p-xylene-bis(1-hydroxy-3-thia-propane) (PXTOH) with α-bromoisobutryl bromide. The PMMA and PS macroinitiators were prepared by ATRP of methyl methacrylate (MMA) and styrene (S) as monomers using (PXTBR) as the initiator and copper(I) bromide/N,N,N',N″,N″-pentamethyldiethylenetriamine (CuBr/PMDETA) as a catalyst system. Secondly, di(α-bromoester) end-functionalized PCL-based ATRP macronitiator (PXTPCLBr) was prepared by esterification of hydroxyl end groups of PCL-diol (PXTPCLOH) synthesized by Sn(Oct)2-catalyzed ring opening polymerization (ROP) of ε-CL in bulk using (PXTOH) as initiator. Finally, ABA-type block copolymers, PXT(PS-b-PMMA-b-PS), PXT(PMMA-b-PS-b-PMMA), PXT(PS-b-PCL-b-PS), and PXT(PMMA-b-PCL-b-PMMA), were synthesized by ATRP of MMA and S as monomers using PMMA-, PS-, and PCL-based macroinitiators in the presence of CuBr/PMDETA as the catalyst system in toluene or N,N-dimethylformamide (DMF) at different temperatures. In addition, the extraction abilities of PCL and PS were investigated under liquid-liquid phase conditions using heavy metal picrates (Ag+, Cd2+, Cu2+, Hg2+, Pb2+, and Zn2+) as substrates and measuring with UV-Vis the amounts of picrate in the 1,2-dichloroethane phase before and after treatment with the polymers. The extraction affinity of PXTPCL and PXTPS for Hg2+ was found to be highest in the liquid-liquid phase extraction experiments. Characterizations of the molecular structures for synthesized novel initiators, macroinitiators, and the block copolymers were made by spectroscopic (FT-IR, ESI-MS, 1H NMR, 13C NMR), DSC, TGA, chromatographic (GPC), and morphologic SEM.

Phytochemical Investigation and Thin Layer Chromatography of Methanol Extract of Psoralea corylifolia and Emblica officinalis Leaves

The current study focuses on phytochemical screening of Psoralea corylifolia and Emblica officinalis leaf extracts in methanol solvent. The antibacterial compounds found in both leaf extracts of Psoralea corylifolia and Emblica officinalis plants were investigated using phytochemical studies. The extracts contained flavonoids, terpenoids, tannins, alkaloids, saponins, and phenolic chemicals, according to preliminary phytochemical screening. The solvent systems of toluene: ethyl acetate: methanol (24:5:2) and chloroform: ethyl acetate: acetic acid (50:50:1) yielded the most phytochemicals from methanolic extracts of Psoralea corylifolia and Emblica officinalis plants, respectively. On TLC plates, these chemicals were separated, resulting in the discovery of different spots in both leaf extracts. The Rf values of methanol extract of P. corylifolia run under toluene: ethyl acetate: methanol (24:5:2) solvent system was 0.12, 0.19, 0.30, 0.41, 0.53, 0.65, 0.77, 0.84, 0.89, and 0.92, respectively, while Rf values of methanol leaf extract of E. officinalis run under chloroform: ethyl acetate: acetic acid (50:50:1)solvent system was 0.23, 0.31, 0.41, 0.64, 0.76 and 0.88 respectively. The results of the investigation will be used to confirm the proper identification of antibacterial fractions from P. corylifolia and E. officinalis crude plant extracts by GC-MS. The optimum solvent for extracting antibacterial components from P. corylifolia and E. officinalis leaves was methanol.

Thermophysical properties of binary mixtures of diethyl ether as oxygenate with cyclohexane and aromatic hydrocarbons

Density (ρ), speed of sound (u), and refractive index (nD) were measured for the binary mixture of diethyl ether (1) + cyclohexane, benzene, and toluene (2) systems at T= (288.15 K to 298.15 K) and 0.1 MPa. The measured data were utilized to calculate excess molar volume (VmE), deviation in ultrasonic speed (Δu), and deviation in refractive index (ΔnD). Our results illustrate that the positive value of VmE and negative value of Δu for diethyl ether + cyclohexane indicate the absence of specific interaction owing to the inert nature of cyclohexane and disruption of the dipole–dipole interactions in diethyl ether during mixing. Conversely, in diethyl ether + benzene or toluene system, the negative values of VmE and positive values of Δu suggest the presence of electron donor–acceptor interactions between the oxygen atom of diethyl ether and the π- electrons of benzene and toluene. These findings were further corroborated by the behavior of the molecular association parameter (MA), which showed that toluene exhibited the greatest value of MA and lower value of VmE compared to benzene, indicating a stronger degree of molecular association due increase in π-electron density because of the presence of electron-donating methyl group in toluene. On the other hand, cyclohexane showed the lowest value of MA, suggesting the disruption of dipole–dipole interaction in diethyl ether. Schaff’s collision factor theory demonstrated high predictive power for ultrasonic speed compared to other models. These experimental data significantly impact advancing theoretical models, process design, material development in chemical industries, and our understanding of the basic behavior of mixtures across various scientific and technical domains.

Quantitative Estimation of Quercetin of Some Selected Edible Plants of West Bengal by High-performance Thin-layer Chromatography Densitometry Method

ABSTRACT Introduction: Quercetin is a polyphenol, widely found in most edible fruits and vegetables. This plant pigment provides cardiovascular, anti-inflammatory, antidiabetic, asthma, and many more health benefits. Objective: The aim of this study is to quantify the quercetin by high-performance thin-layer chromatography (HPTLC) method from the methanolic leaf extracts of three edible plants of Bengal, viz., Nyctanthes arbor-tristis L., Oxalis corniculata L., and Polygonum plebeium R.Br. Materials and Methods: HPTLC was carried out on aluminum-backed plate precoated with silica gel 60 F254, using the solvent system of toluene, ethyl acetate, formic acid, and methanol (5.5:3:1:0.5 v/v/v/v). The method validation was done according to the International Conference on Harmonization guidelines in terms of linearity, limit of detection, limit of quantification, accuracy, precision, and specificity. Results: The desired compound was well separated using the solvent system toluene, ethyl acetate, formic acid, and methanol (5.5:3:1:0.5 v/v/v/v) which gave a sharp and well-defined band with Rf 0.60 for quercetin. The calibration curves showed a good linear correlation coefficient (R 2 = 0.9774). The linearity range was found to be 20–100 (μg/spot). Among the selected plants, the highest amount of quercetin was found in the leaf extracts of O. corniculata L. (220.035 ± 0.06 mg/100 g) and the lowest for N. arbor-tristis L. (31.253 ± 0.99 mg/100 g). Conclusion: The proposed HPTLC method for quercetin estimation was found to be simple, cost-effective, precise, and accurate and can be used for the quality control of plant material. O. corniculata L. was found to be a potent source of quercetin as it possesses a decent amount of quercetin.

Study on catalytic degradation of toluene by copper manganese composite oxide

AbstractHerein, Cu–Mn catalysts were used to study the catalytic oxidation system of toluene, revealing the optimal preparation conditions for catalytic oxidation of toluene and the effects of other factors on catalytic performance (oxygen concentration, toluene concentration, temperature, humidity, space velocity). The as‐synthesized Cu2Mn1Ox exhibited the best catalytic activity and stability. The BET, XRD, and O2‐TPD results indicated that the synthesized Cu2Mn1 catalyst can effectively form the Cu1.4Mn1.6O4 phase at the optimal calcination temperature (500–600°C) and accelerate the toluene degradation at 220°C. Although water vapor can promote the progress of catalytic reactions, excessive water vapor tends to form competitive adsorption at active sites, inhibiting the progress of catalytic reactions. In addition, oxygen concentration plays a key role in catalytic reactions. Based on the results, it was found that at lower oxygen concentrations or higher toluene concentrations, the catalyst was easy to react with toluene to generate Cu and MnO, resulting in catalyst deactivation.

Future of hydrogen economy: simulation-based comparison of LOHC systems

Hydrogen is one of the key components in renewable energy systems. Its storage and transport, however, are challenging. The Liquid Organic Hydrogen Carrier (LOHC) technology is a possible solution for this issue. With suitable organic components, hydrogen can be stored in a chemically bound form which is safer and has a higher energy density than other solutions. Furthermore, the storage and transport of the LOHC component with high hydrogen content can be provided under normal environmental conditions. The LOHC process cycle involves a catalytic hydrogenation and dehydrogenation step where the LOHC component can be recovered and recycled. The paper reviews a few relevant studies regarding the possible LOHC compound pairs, the potential catalyst systems, and the necessary equipment. Then, the paper discusses a simulation study of three LOHC systems, determining suitable operating conditions and estimating costs. The toluene-methylcyclohexane system was found to be the most promising for LOHC application. Two energy integration opportunities were also examined. The first case study was based on separate hydrogenation and dehydrogenation sites, while the second was based on one site utilization. The results show a lower energy demand in the case of a toluene system, with a reduction of 70% in heating and 45% in cooling.Graphical

Aromatic volatile organic compounds absorption with phenyl‐based deep eutectic solvents: A molecular thermodynamics and dynamics study

AbstractThe suitability of phenyl‐based deep eutectic solvents (DESs) as absorbents for toluene absorption was investigated by means of thermodynamic modeling and molecular dynamics (MD). The thermodynamic models perturbed‐chain statistical associating fluid theory (PC‐SAFT) and conductor‐like screening model for real solvents (COSMO‐RS) were used to predict the vapor–liquid equilibrium of DES–toluene systems. PC‐SAFT yielded quantitative results even without using any binary fitting parameters. Among the five DESs studied in this work, [TEBAC][PhOH] consisting of triethyl benzyl ammonium chloride (TEBAC) and phenol (PhOH), was considered as the most suitable absorbent. Systems with [TEBAC][PhOH] had lowest equilibrium pressures of the considered DES–toluene mixtures, the best thermodynamic characteristics (i.e., Henry's law constant, excess enthalpy, Gibbs free energy of solvation of toluene), and the highest self‐diffusion coefficient of toluene. The molecular‐level mechanism was explored by MD simulations, indicating that [TEBAC][PhOH] has the strongest interaction of DES–toluene compared to the other DESs under study. This work provides guidance to rationally design novel DESs for efficient aromatic volatile organic compounds absorption.

Pressure-driven flow behavior of small molecules through a carbon nanotube

In this research, the flow behavior of ring and chain molecules through a carbon nanotube (CNT) driven by pressure has been investigated using molecular dynamics (MD) simulations. We have examined the distribution of fluid molecules and the flow process confined in the CNT. We also calculated the radial count profiles, the axial density distributions, molecular conformation and fluid flux. Our results revealed that a sudden pressure applied on fluid molecules will lead to inrush of fluid inside nanoscale channels. The fluid molecules confined in the CNT formed an interfacial layer near the CNT inner surface. That of toluene system is closer to the CNT wall than heptane system. The results also indicated that plane of toluene molecules in interfacial layer is parallel to the CNT wall. The distributions of the others are disordered. The heptane molecules formed four cylindrical layers inside the CNT. The molecules in interfacial layer are parallel to the CNT wall.

Efficient biocatalytic synthesis of green plasticizer 2,5-furanediformate isooctyl ester using an immobilized lipase.

2,5-furanediformate Isooctyl is a potential new green biobased plasticizer. At present, most of the preparation methods are chemical methods, which not only have many by-products and are difficult to separate, but also cause environmental pollution. In this paper, the immobilized lipase Novozym435 was used as the catalyst to catalyze the transesterification of 2,5-furanediformate dimethyl ester and isooctyl alcohol to prepare 2,5-furanediformate isoocty in organic medium, and the reaction process was optimized. The optimal process conditions were determined by single factor experiment: in 10 mL toluene system, the additional amount of immobilized lipase Novozym435 was 0.02 g, the molar ratio of 2,5-furanediformate dimethyl ester (1 mmol) and isooctyl alcohol was 1:4, and 1 g 4Å molecular sieve was added to the reaction system, the reaction temperature was 50°C, the reaction time was 24 h, and the conversion rate of 2,5-furanediformate isoocty was 89.63%.

Can DLVO theory be applied to MOF in different dielectric solvents?

ZIF-8 is widely used as a porous crystal material in the field of colloids. Its interfacial interactions are crucial to the performance of colloidal particles. In this paper, the Hamaker constant of ZIF-8 (3.45 × 10−20 J) was calculated for the first time by contact angle measurement parameters. The non-retarded Hamaker constant of ZIF-8 (4.66 × 10−21 J) was calculated using the Lifshitz's theory. Its dispersion in the dipolar (water) and monopolar (toluene) solvent systems was discussed using DLVO theory. The results showed that the energy potential barrier reached +183.9 KBT in the water system. However, the particles tended to be unstable in the toluene system, which did not correspond to the experimental phenomena we observed. Using the XDLVO theory, we took the Lewis acid-base fraction as an object of investigation, and the results showed that the hydrophobic attraction force between particles was 102 mJ/m2 in the dipolar solvent (water). In the monopolar system, the steric repulsion was linked to the Lewis acid-base fraction of the particles. XDLVO theory can better describe the dispersion of ZIF-8 particles in different solvents. In future work, it is necessary to consider the Lewis acid-base surface energy due to crystal defects, especially for the interfacial interaction between solvent and particles during the preparation of colloidal suspensions.

Spectrophotometric determination of cadmium(II) with a new thiazolylazo reagent

Controlling the content of heavy metals in environmental objects at the level of their maximum permissible concentrations is an important analytical task. The widely used physicochemical methods do not always provide a direct solution to this problem due to the influence of the matrix composition of the sample on the results of determinations, as well as low concentrations of the determined elements. Therefore, targeted synthesis and search for inexpensive and effective technologies for analytical control of heavy toxic metals is still relevant. 1,3-triazole derivatives such as 1-(2-thiazolylazo)-2-naphthol are available compounds. They are produced on an industrial scale. The weak basic and complexing properties of these compounds are due to the presence of a triazole ring in their structure. Extraction is one of the most widespread methods for the isolation and separation of substances and is widely used in technology and analysis. The spectral characteristics of the Cd(II)-1-[5-(4-methylbenzyl)-1,3-thiazol-2-yl)] azonaphthalen-2-ol (MBnTAN) system in toluene were studied for the first time. Optimal interaction conditions for 1-[5-(4-methylbenzyl)-1,3-thiazol-2-yl] azonaphthalen-2-ol with cadmium were established, namely: acidity of the medium (the compound is formed in an alkaline medium at pH = 11.0); the ratio of the components of the complex compound cadmium: reagent is 1:2; maximum light absorption of the Cd-MBnTAN complex at λ = 588 and 610 nm. The effective molar coefficient of light absorption is 1.05∙10 4 l∙mol -1 ∙cm -1 . A sensitive spectrophotometric method for the determination of Cd (II) using MBnTAN with a detection limit of 0.5 μmol/l has been developed and the limits of the linear dependence of the optical density on the concentration of 2.4 to 12.0 μmol/l. The developed method for determining Cd(II) was tested on model solutions. Keywords : сadmium(II), extraction, spectrophotometry, azodyes.