Solvent Dilution Research Articles

Density functional theory study with and without COSMO of H2 SO4 reactions in an aqueous environment for metal extraction.

In a recent study investigating the suitability of solvent extraction (SX) for the separation of Ta and Nb, it was shown that speciation data would be required to help explain the data obtained. As traditional speciation techniques cannot be readily applied for Ta and Nb, it was decided to determine the suitability of molecular modeling for this purpose. During the SX experiments the aqueous phase consisted of sulfuric acid (H2 SO4 ), water, and metal species. In this study density functional theory (DFT) modeling was used to calculate the formation energy of five possible reactions of H2 SO4 and H2 O. Different functional and basis set combinations were compared as well as the effect of infinite dilution by using the conductor-like screening model (COSMO), which simulates infinite dilution of solvents of varying polarity and includes the short-range interactions of the solute particles. The results obtained were used to determine whether it is possible to predict the reactions and mechanism when H2 SO4 and H2 O interact during SX. According to the results, the deprotonation of H2 SO4 was endothermic in a 1:1 acid-water ratio, while being both exothermic in the 1:5 and 1:10 acid-water ratio forming HSO4 - and SO4 2- respectively. Furthermore, it was seen that the hydration and dehydration of H2 SO4 in a bulk H2 O solution was a continuous process. From the energy calculations it was determined that although the H2 SO4 ●H2 O, HSO4 - ●H2 O, and H2 SO4 ●2H2 O species could form, they would most likely react with H2 O molecules to form HSO4 - , H3 O+ , and H2 O. © 2018 Wiley Periodicals, Inc.

Speciation Analysis of Arsenic Compounds by HPLC-ICP-MS: Application for Human Serum and Urine.

A high-performance liquid chromatography (HPLC) in combination with inductively coupled plasma mass spectrometry (ICP-MS) as an elemental specific detector was used for the speciation analysis of arsenic compounds in urine and serum samples from Vietnam. Five arsenic species including arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and arsenobetaine (AsB) were studied. A gradient elution of ammonium carbonate ((NH4)2CO3), ethylenediaminetetraacetic acid disodium salt (Na2EDTA), and methanol at pH 9.0 utilizing Hamilton PRP-X100 strong anion-exchange column allowed the chromatographic separation of five arsenic species. In this study, urine and serum samples were prepared by dilution in solvent and protein precipitation by trichloroacetic acid, respectively. The extraction efficiency was greater than 91% for urine matrix, and recoveries from spiked samples were in the range of 94–139% for the arsenic species in human serum. The method limit of detection (MDL) and limit of quantification (MQL), which were calculated by signal to noise ratio, were found to be 0.3–1.5 and 1.0–5.0 ng·mL−1, respectively. The concentration of arsenic species in 17 pairs of urine and serum samples from Vietnam was also quantified and evaluated. The major species of arsenic in the urine and serum samples were AsB and DMA.

Pharmaceutical Preparations for Intradermal Drug Tests

AbstractOur department of pharmacy takes over all the medical skin tests prescribed by the allergy department. The production takes place in specific premises, with qualified and calibrated equipment, by a qualified and regularly assessed staff—in compliance with the French preparation guidelines. The whole activity is under the responsibility of a pharmacist—handlings are performed by hospital pharmacy technicians. Each new intradermal skin test demand leads to a feasibility analysis—irritating nature, dilution solvent, concentration—this information is gathered in a thesaurus. The manufacturing steps are the following: prescription validation, production sheet and label printing, preparation of the needed equipment, batch numbers and expiration date checking, handling under a vertical laminar flow hood and control after production. The preparation activity increases continuously and the thesaurus currently contents 302 rows with following information: drug, dilution and reconstitution solvent, pure solution concentration and maximum concentration to test with intradermal tests. Work would prospect in costs reduction and resources optimization. Thanks to the allergists’ confidence, the partnership between the two departments can go on. This guarantees the quality of the preparations tested on patients but also the skin tests reproducibility.

Physicochemical and Electrochemical Compatibility of High-Concentrated Solvate Ionic Liquids and Low-Viscosity Dilute Solvent

Lithium-sulfur battery has been attracted attention as a next-generation battery of large capacity. Lithium-sulfur battery has reversible theoretical capacity of 1,672mA h g-1. This is 10 times the theoretical capacity compared with conventional positive electrode materials such as LiCoO2 using Li-ion battery. One serious problem of lithium sulfur battery is dissolution of lithium polysulfide (Li2S x ) as reaction intermediate into the electrolyte solution during charge/discharge reaction. This causes degradation of the charge/discharge cycle characteristics and coulombic efficiency of the battery. In order to solve this problem, “solvate ionic liquid (SIL)” is proposed as new electrolyte, because dissolution of Li2S x can be suppressed owing to weak Lewis acidity/basicity. For example, significant improvement for stability of electrolyte solution has been reported by high-salt concentration (ether series[1]/acetonitrile[2]) owing to strong interaction between Li salt and solvent molecule. However, high-concentration electrolyte exhibits large viscosity. And the electrolyte systems has risks of rate performance for high rate charge/discharge operations. Therefore, in order to obtain low viscosity electrolyte, we proposed to add low viscosity dilute solvent into electrolyte[3]. Most important demands for dilute solvent are, Improvement of rate performances for batteries by low viscosity of electrolyte solutionStabilization of solvated structure between Li salt and solvent molecule with/without dilute solvent. In this study, we investigated physicochemical effects for understanding compatibility of two effective approaches of super-concentrated Li salt electrolyte and non-interactive dilute solvent. In this study SIL sample, [Li(G4)0.8]TFSA (G4: CH3-O-(C2H4O)4-CH3, TFSA:N(SO2CF3)2) was prepared in Ar-filled glovebox. Molar ratio of [Li(G4)0.8]TFSA was G4:LiTFSA=0.8:1. In addition We added given amount of 1,1,2,2, - tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (HFE) dilute solvent into SIL, and measured temperature dependences of viscosity and density of prepared sample. Fig.1(a) showed the composition dependences of the viscosity from 10 to 80℃ (h) for SIL/HFE mixtures. We confirmed that diluting HFE decreased viscosity [Li(G4)0.8]TFSA. Fig.1(b) showed the temperature dependences of the density from 10 to 80℃ (ρ) for SIL/HFE mixtures. ρ values of HFE were larger than that of SIL ones owing to the difference of fluorine density between SIL and HFE. At this time, we assumed SIL as one molecule, excess densities (E ρ) were expressed as following, E ρ=ρ-(xρSIL+(1-x)ρHFE) Where x, ρSIL and ρHFE are mole fraction of SIL, ρ of neat SIL and HFE, respectively. Fig.1(c) shows mole fraction dependences of E r for SIL-HFE mixtures. E r always shows a negative value in the temperature range below 30℃. Therefore, by mixing SIL and HFE, and suggested that the density decreasing. This result correlated with spectroscopic method that coordination structure of SIL and G4 doesn’t change significant in dilute HFE[4]. In this presentation, relationships between lithium-sulfur battery performance (rate properties) and composition of [Li(G4)0.8]TFSA/HFE will be reported, and also will be discussed optimum dilution amount of HFE. Reference s : [1]K. Yoshida et al, J. Am, Chem. Soc. 2011, 133, 13121. [2]Y. Yamada et al, J. Am. Chem. Soc. 2014, 136, 5039. [3]K. Dokko et al, J. Electrochem. Soc. 2013, 160, A1304. [4]S. Saito et al, J. Phys. Chem. B 2016, 120, 3378. Figure 1

The Effect of pH on Fuel-Cell Catalyst-Layer Inks

Fuel cell catalyst layers are cast from inks containing a solvent, an ionomer, and catalyst particles. Though there are generally accepted material classes (water/alcohol mixtures for the solvent, perfluorosulfonic acid (PFSA) polymers, and Pt-alloy based catalyst particles supported on carbon), there are no standard ratios or metrics for ink formulation. As such, ink recipes have been highly empirical to date, with little understanding of the governing interactions controlling resultant properties and behavior. This study therefore aims to systematically investigate the effect of pH on ink aggregation and rheology. Solvent choice greatly influences the morphology of PFSAs in solution1-4, which in turn alters pH. Starting with a solvent-ionomer compositional matrix, solvent versus pH effects are decoupled. Using dynamic and electrophoretic light scattering, rheology, and direct visualization with cryo electron microscopy, particle-solvent-ionomer systems are then studied to understand aggregation, stability, and rheology under various pH conditions. AcknowledgementsThis work was mainly funded under the Fuel Cell Performance and Durability Consortium (FC PAD) funded by the Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231. S.A.B also acknowledges support from National Science Foundation Graduate Research Fellowship under Grant No. DGE 1106400. References Welch, C.; Labouriau, A.; Hjelm, R.; Orler, B.; Johnston, C.; Kim, Y. S., Nafion in Dilute Solvent Systems: Dispersion or Solution? ACS Macro. Lett. 2012, 1 (12), 1403-1407.Ma, C.-H.; Yu, T. L.; Lin, H.-L.; Huang, Y.-T.; Chen, Y.-L.; Jeng, U. S.; Lai, Y.-H.; Sun, Y.-S., Morphology and properties of Nafion membranes prepared by solution casting. Polymer 2009, 50 (7), 1764-1777.Lee, S.-J.; Yu, T. L.; Lin, H.-L.; Liu, W.-H.; Lai, C.-L., Solution properties of nafion in methanol/water mixture solvent. Polymer 2004, 45 (8), 2853-2862.Gebel, G.; Loppinet, B., Colloidal structure of ionomer solutions in polar solvents. J. Mol. Struct. 1996, 383 (1), 43-49.

Effect of solvents on the microstructure aggregation of a heavy crude oil

We study the asphaltene microstructure in a heavy crude oil in response to the addition of solvents of different qualities by measuring the intrinsic viscosity and the Huggins coefficient. Dilution with good solvents (xylene and cyclohexanone) causes the native asphaltene clusters swelling, while that with poor solvents (a diesel oil and a C11-C14 alkanes mixture) may induce different microstructural rearrangements. The mixture of C11-C14 alkanes induces the aggregation of clusters, while the diesel oil their shrinkage. Moreover, if the diesel is added in small quantities instead of cluster shrinkage it may induce cluster aggregation thus forming larger “macro-clusters”. These structures survive after further dilution in both poor and good solvents and their formation is always accompanied by a reduction of the Huggins coefficient that implies the better solubility of these self-aggregated structures in the used solvent. Finally, an unusual negative Huggins coefficient is measured, when the macro-clusters are formed and the solution is diluted in a good solvent. This might be due to a prevalence of the intra-macro-cluster interactions on the inter-macro-cluster ones.

Formulation and Characterization of Cubosomes Containing REB for Improvement of Oral Absorption of the Drug in Human Volunteers

Objectives: To prepare rebamipide (REB) -loaded cubosomal nanoparticles to improve the oral bioavailability of the drug in human volunteers. Methodology: The poorly water soluble drug REB was incorporated into cubosomal nanoparticles by solvent dilution method. The prepared REB-loaded cubosomes were in vitro characterized for particle size, polydispersity index (PDI), zeta potential, drug crystallinity and in vitro drug release. In vivo absorption of REB-loaded cubosomes was compared with drug powder and commercially available tablets Mucosta® (Egypt Otsuka Pharmaceutical Company) in healthy human volunteers. Results: In vitro, REB-loaded cubosomes entrapped about 82.44 % drug and revealed nanometer-size ranged from 303.1 ± 4.9 to 444.9 ± 6 nm. In vitro REB release from cubosomes exhibited a phase of rapid and high release of the drug during the first hour followed by a slower and complete drug release over a period of 3 hrs. The results of bioavailability study in healthy human volunteers showed that cubosomes significantly improved the rate and extent of REB absorption. The mean relative bioavailability of the REB loaded cubosomes compared to the drug powder and commercially available tablets (Mucosta®) was 191.23 ± 1.24 % and 166.29 ± 1.14 % respectively. Conclusion: The prepared cubosomes significantly improved the In-vivo absorption of REB in comparison with drug powder and commercially available tablets (Mucosta®).

Development of an Analytical Method for Analyzing Pyrrolizidine Alkaloids in Different Groups of Food by UPLC-MS/MS

Suspected nontargeted pyrrolizidine alkaloids (PAs), without analytical reference standard, were observed and interfered with the determination of targeted PAs in complex food matrices, especially for spices samples. Selectivity and applicability of multiple reaction monitoring (MRM) transitions, multistage fragmentation (MS3), and MRM with differential ion mobility spectrometry (DMS) for eliminating false positive identifications were evaluated. Afterward, a selective and sensitive LC-MS/MS method for the determination of 15 PAs and 13 PA N-oxides in foodstuffs was developed. The sample preparation and cleanup are applicable to a wide range of foodstuffs, including cereal products, dairy products, meat, eggs, honey, tea infusion, and spices. Freezing-out of the raw extract and the water/acetonitrile washing steps in a solid phase extraction was found to efficiently remove complex matrices. The method was validated at 0.05 μg kg-1 for general food and 0.5 μg kg-1 for spices, with reference to the Eurachem Guide. The estimated limit of quantifications of different PAs was in the range of 0.010-0.087 μg kg-1 for general food and 0.04-0.76 μg kg-1 for spices. Isotopically labeled PAs were used as internal standards to correct the variation of PAs/PANs performance in different food commodities. Matrix effects observed in complex food matrices could be reduced by solvent dilution. Recoveries of PAs and PA N-oxides were all seen within 50-120%.

Quantitative Characterization of Metastability and Heterogeneity of Amyloid Aggregates

Amyloids are heterogeneous assemblies of extremely stable fibrillar aggregates of proteins. Although biological activities of the amyloids are dependent on its conformation, quantitative evaluation of heterogeneity of amyloids has been difficult. Here we use disaggregation of the amyloids of tetramethylrhodamine-labeled Aβ (TMR-Aβ) to characterize its stability and heterogeneity. Disaggregation of TMR-Aβ amyloids, monitored by fluorescence recovery of TMR, was negligible in native buffer even at low nanomolar concentrations but the kinetics increased exponentially with addition of denaturants such as urea or GdnCl. However, dissolution of TMR-Aβ amyloids is different from what is expected in the case of thermodynamic solubility. For example, the fraction of soluble amyloids is found to be independent of total concentration of the peptide at all concentrations of the denaturants. Additionally, soluble fraction is dependent on growth conditions such as temperature, pH, and aging of the amyloids. Furthermore, amyloids undissolved in a certain concentration of the denaturant do not show any further dissolution after dilution in the same solvent; instead, these require higher concentrations of the denaturant. Taken together, our results indicate that amyloids are a heterogeneous ensemble of metastable states. Furthermore, dissolution of each structurally homogeneous member requires a unique threshold concentration of denaturant. Fraction of soluble amyloids as a function of concentration of denaturants is found to be sigmoidal. The sigmoidal curve becomes progressively steeper with progressive seeding of the amyloids, although the midpoint remains unchanged. Therefore, heterogeneity of the amyloids is a major determinant of the steepness of the sigmoidal curve. The sigmoidal curve can be fit assuming a normal distribution for the population of the amyloids of various kinetic stabilities. We propose that the mean and the standard deviation of the normal distribution provide quantitative estimates of mean kinetic stability and heterogeneity, respectively, of the amyloids in a certain preparation.

Nozzle Printed-PEDOT:PSS for Organic Light Emitting Diodes with Various Dilution Rates of Ethanol

In this study, we investigated the ink formulation of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the hole injection layer (HIL) in an organic light emitting diode (OLED) structure. Generally, in a PEDOT:PSS solution, water is incorporated in the solution for the solution process. However, the fabrication of thin film which contained the water, main solvent, could not easily form by using printing technology except spin-coating process because of the high surface tension of water. On the other hand, mixing PEDOT:PSS solution and ethanol (EtOH), a dilution solvent, could restrain the non-uniform layer that forms by the high surface tension and low volatility of water. Therefore, we printed a PEDOT:PSS solution with various concentrations of EtOH by using a nozzle printer and obtained a uniform pattern. The line width of PEDOT:PSS diluted with 90% (volume ratio) ehtanol was measured as about 4 mm with good uniformity with a 0.1 mm nozzle. Also, imaging software and a scanning electron microscope (SEM) were used to measure the uniformity of PEDOT:PSS coated on a substrate. Finally, we fabricated a green phosphorescent OLED device with printed-PEDOT:PSS with specific concentrations of EtOH and we achieved a current efficiency of 27 cd/A with uniform quality of luminance in the case of device containing 90% EtOH.

High-resolution patterning of silver nanopaste containing volatile solvents achieved with gas-permeable mold

Sub-400-nm high-resolution and -accuracy nanopatterning of silver nanopaste containing volatile solvents was demonstrated by thermal nanoimprint lithography using a porous, cyclodextrin-based, gas-permeable mold for the application of high-surface-area heat sinks. The silver nanoparticles have desirable heat-radiation characteristics. However, high-resolution and accurate nanopatterning of silver nanoparticles by thermal nanoimprint lithography is challenging because volatile dilution solvents, which are contained in nanoparticle pastes for high fluidity, can be trapped by gas-impermeable molds to cause pattern failures. The normalized heat-transfer amount of the 380-nm dense-line pattern of silver was calculated to be three times than that of the existing 10-μm dense-line pattern.

Intramolecular HB Interactions Evidenced in Dibenzoyl Oxalamide Derivatives: NMR, QTAIM, and NCI Studies.

Extensive NMR spectroscopic studies revealed information on the occurrence of bifurcated intramolecular hydrogen bond in the dibenzoyl oxalamide derivatives. One-dimensional NMR experiments, viz., solvent dilution, temperature perturbation, and two-dimensional experimental techniques, such as 15N-1H HSQC and 19F-1H HOESY, have been exploited to derive unambiguous confirmation of the participation of organic fluorine in the hydrogen-bonding interaction. The experimental NMR findings have been ratified by density functional theory based calculations, viz., NCI (noncovalent interaction) and QTAIM (quantum theory of atoms in molecules).

Simple Spectrophotometric Method for Determination of Iron in Crude Oil

In this research article, spectrophotometric method for the determination of iron with 1,10-phenanthroline (phen) in two different crude oil samples from different oil fields in the Suez-Gulf region of Egypt has been proposed. The method is efficient, reliable and inexpensive where a cost-effective technique, along with commercially available spectrophotometric reagent, was utilized in this work. The method was based on decomposition of the organic matrix by combustion in a heating muffle furnace at 550°C. The inorganic residue was then dissolved in diluted nitric acid and the iron was reduced to the divalent state. The color was developed by the addition of 1,10-phenanthroline as chelating agent after adjusting the pH of the solution, then the absorbance of the solution was measured at approximately 510 nm after a short reaction period. The limit of detection (LOD) and limit of quantification (LOQ) obtained were found to be 0.017 and 0.051 μg/mL, respectively. The effect of interferences was studied and the accuracy of the method was evaluated by recovery experiment, analysis of oil reference material and by comparison of results with those obtained using flame atomic absorption spectrometer (FAAS) after dilution in an organic solvent for sample preparation.

A Low-Molecular-Weight Gelator Composed of Pyrene and Fluorene Moieties for Effective Charge Transfer in Supramolecular Ambidextrous Gel.

Charge-transfer (CT) gel materials obtained from low-molecular-weight (LMW) compounds through a supramolecular self-assembly approach have received fascinating attention by many researchers because of their interesting material property and potential applications. However, most of the CT gel materials constructed were of organogels while the construction of CT gels in the form of a hydrogel is a challenge because of the solubility issue in water, which considerably limits the use of CT hydrogels. Herein, for the first time, we report a new LMW gelator [Nα-(fluorenylmethoxycarbonyl)-Nε-(δ-butyric-1-pyrenyl)-l-lysine, (FmKPy)], composed of two functional moieties such as fluorenylmethoxycarbonyl and pyrene, which not only parade both hydro and organo (ambidextrous) supramolecular gel formation but also exhibit CT ambidextrous gels when mixed with an electron acceptor such as 2,4,7-trinitro-9-fluorenone (TNF). This finding is significant as the established CT organogelator in the literature did not form an organogel in the absence of an electron acceptor or lose their gelation property upon the addition of the acceptor. CT between pyrene and TNF was confirmed by the color change as well as the appearance of the CT band in the visible region of the absorption spectrum. CT between FmKPy and TNF was supported by the solvent dilution method using tetrahydrofuran as the gel breaker and pyrene fluorescence quenching in the case compound containing pyrene and TNF. The morphology of FmKPy ambidextrous gels indicates the fibrous nature while the self-assembled structure is primarily stabilized by π-π stacking among fluorenyl and pyrenyl moieties and hydrogen bonding between amide groups. The FmKPy-TNF CT ambidextrous gel retains the fibrous nature; however, the size of the fibers changed. In FmKPy-TNF CT gels, TNF is intercalated between pyrene moieties in the self-assembled structure as confirmed by fluorescence quenching and powder X-ray diffraction. The FmKPy ambidextrous gel exhibits significant properties such as low minimum gelation concentration (MGC), thixotropic nature, pH stimuli response, and high thermal stability. Upon the addition of TNF, the FmKPy-TNF CT ambidextrous gel maintains all these properties except MGC which increased for FmKPy-TNF. Because pyrene-based LMW organogels have been developed widely for many applications while their hydrogels were limited, the current finding of the pyrene-based ambidextrous fluorescent gel with the CT property provides a wide opportunity to use FmKPy as a soft material maker and also for potential applications in fields like surface coating, three-dimensional printing, and so forth.

Partial molar volume of NaCl and CsCl in mixtures of water and methanol by experiment and molecular simulation

Densities of solutions of NaCl and CsCl in mixtures of water and methanol are determined by experiment and molecular dynamics simulation. Both experiments and simulations cover the concentration range up to the solubility limit of the salt in the temperature range 288.15 ≤T /K ≤ 318.15 at ambient pressure. Non-polarizable molecular models from the literature are used for the ions and solvents. The partial molar volume of the salts at infinite dilution in the mixed solvent is determined from an empirical correlation of the data. The mixed solvent effects on the density and the partial molar volumes of the salts are well predicted by the molecular models.

Hydrophobicity of hemp shiv treated with sol-gel coatings

This is the first time sol-gel technology is used in the treatment of hemp shiv to develop sustainable thermal insulation building materials. The impact on the hydrophobicity of hemp shiv by depositing functionalised sol-gel coatings using hexadecyltrimethoxysilane (HDTMS) has been investigated. Bio-based materials have tendency to absorb large amounts of water due to their hydrophilic nature and highly porous structure. In this work, the influence of catalysts, solvent dilution and HDTMS loading in the silica sols on the hydrophobicity of hemp shiv surface has been reported. The hydrophobicity of sol-gel coated hemp shiv increased significantly when using acid catalysed sols which provided water contact angles of up to 118° at 1% HDTMS loading. Ethanol diluted sol-gel coatings enhanced the surface roughness of the hemp shiv by 36% as observed under 3D optical profilometer. The XPS results revealed that the surface chemical composition of the hemp shiv was altered by the sol-gel coating, blocking the hydroxyl sites responsible for hydrophilicity.

Direct detection of organophosphate compounds in water by a fluorescence-based biosensing device

The main drawbacks in the use of acetylcholinesterase-based biosensors are their susceptibility to inhibition by too many chemicals, their limited time-stability, and the constant need for a supply of substrates for the measurements. In order to offset these deficiencies, we have addressed our studies towards the thermophilic esterase 2 from A. acidocaldarious, which shows a high specificity and affinity towards organophosphates and a high resistance under raw operative conditions. In particular, we have investigated the possibility of measuring the binding of organophosphates to the protein by using a fluorescent probe covalently linked near the active site. We have produced a mutant where the serine 35, a residue located at the entrance of the alcohol binding site, has been replaced by a cysteine residue. The addition of 1,5-IAEDANS as a fluorescent probe to the thiol group of the mutant-protein did not affect the capability of the enzyme to bind the paraoxon and its stability or instability over time. We have set up a continuous flow system based on a re-circulating solution of the probe-enzyme complex through a fluorimetric flow cell inside a spectrofluorimeter. The addition of paraoxon aliquots has been detected in real-time by measuring the fluorescence quenching of the probe-enzyme complex. The fluorescence signals, as well as the enzyme activity, were not affected by dilution and organic solvent addition. These results support the development of biosensing devices for the continuous monitoring of organophosphate compounds.

Experimental validation of equilibrium based mathematical modelling of liquid‐liquid phase transfer catalysis

The reaction between two compounds which reside in immiscible phases can be accelerated using a phase transfer catalyst. The catalyst helps to transfer a species ion from one phase to the other phase, thus promoting its reaction. Several mechanisms have been proposed to describe phase transfer catalyzed reactions. In this work, we have carried out an experimental and theoretical study of phase transfer catalysis in batch mode. A mathematical model is developed which helps to predict the progress of the reaction under different operating conditions. Here the different species in the aqueous phase are assumed to be in equilibrium and these react with the species in the organic phase. The effect of diffusional resistance inside the dispersed organic phase is shown to be negligible. The two reaction systems studied are the phase transfer catalyzed (i) thioetherification and (ii) benzyl alcohol oxidation using sodium hypochlorite. Batch experiments were performed to determine the effect of catalyst loading, solvent dilution, and pH. The experimental results show that with an increase in catalyst loading, the phase transfer catalyzed reactions were accelerated. The use of a minimal amount of solvent results in a better performance. Benzyl alcohol oxidation is favoured under low pH conditions. The developed model is able to capture the performance of the system over a wide range of operating conditions accurately.

Comparison of Preparation Methods for the Determination of Metals in Petroleum Fractions (1000 °F+) by Microwave Plasma Atomic Emission Spectroscopy

Microwave induced plasma atomic emission spectroscopy (MP-AES) with nitrogen gas was employed for the determination of trace elements in petroleum fractions with a boiling point above 1000 °F, using direct dilution in an organic solvent. Nitrogen produces robust plasma for the analysis of fractions having an American Petroleum Institute (API) gravity range from −2° up to 9.7° and elemental composition as follows: S (1.0–5.5 wt %) and N (200–14 000 mg kg–1). A satisfactory limit of quantification and spike recoveries at low and high concentration levels were determined for Na, K, Ca, V, Fe, Ni, and Mo present in different residua samples. The recoveries obtained from the analysis of three QC test materials were within ±10% of the actual and or certified values. It was found that V, Fe, and Ni are the most predominant elements present in these samples and the effect of the source of sustained plasma gas as well as sample preparation method was focused on the quantification of these three elements. Using a d...

Controlled Crystal Grain Growth in Mixed Cation-Halide Perovskite by Evaporated Solvent Vapor Recycling Method for High Efficiency Solar Cells.

We developed a new and simple solvent vapor-assisted thermal annealing (VA) procedure which can reduce grain boundaries in a perovskite film for fabricating highly efficient perovskite solar cells (PSCs). By recycling of solvent molecules evaporated from an as-prepared perovskite film as a VA vapor source, named the pot-roast VA (PR-VA) method, finely controlled and reproducible device fabrication was achieved for formamidinium (FA) and methylammonium (MA) mixed cation-halide perovskite (FAPbI3)0.85(MAPbBr3)0.15. The mixed perovskite was crystallized on a low-temperature prepared brookite TiO2 mesoporous scaffold. When exposed to very dilute solvent vapor, small grains in the perovskite film gradually unified into large grains, resulting in grain boundaries which were highly reduced and improvement of photovoltaic performance in PSC. PR-VA-treated large grain perovskite absorbers exhibited stable photocurrent-voltage performance with high fill factor and suppressed hysteresis, achieving the best conversion efficiency of 18.5% for a 5 × 5 mm2 device and 15.2% for a 1.0 × 1.0 cm2 device.