Utilizing a Rapid Multi-Plug Filtration Cleanup Method for 72 Pesticide Residues in Grape Wines Followed by Detection with Gas Chromatography Tandem Mass Spectrometry

A convenient and fast multi-residue method for the efficient identification and quantification of 72 pesticides belonging to different chemical classes in red and white grape wines has been developed. The analysis was based on gas chromatography tandem quadrupole mass spectrometric determination (GC–MS/MS). The optimization strategy involved the selection of the amount of multi-walled carbon nanotubes (MWCNTs) and the number of cleanup procedure cycles for multi-plug filtration cleanup (m-PFC) to achieve ideal recoveries and reduce the sample matrix compounds in the final extracts. The optimized procedure obtained consistent recoveries between 70.2 and 108.8% (70.2 and 108.8% for white wine, and 72.3 and 108.4% for red wine), with relative standard deviations (RSDs) that were generally lower than 9.2% at the three spiking levels of 0.01, 0.05 and 0.1 mg/kg. The linearity was studied in the range between 0.002 and 0.1 mg/kg using pesticide standards prepared both in pure solvent and in the presence of the matrix, showing coefficients of determination (R2) higher than 0.9495 for all the pesticides. To improve accuracy, matrix-matched calibration curves were used for calculating the quantification results. Finally, the method was used successfully for detecting pesticide residues in commercial grape wines.

Ideal Solutions and Colligative Properties

Ideal Solutions and Colligative Properties deals with the properties of solutions that depend on the concentration, but not the identity, of solute particles. The discussion examines the solution properties of vapour pressure depression, boiling point elevation, freezing point depression and osmotic pressure for an ideal solution, and how they differ from the properties of the pure solvent. Raoult’s law is used to quantify the magnitude of vapour pressure lowering. This is followed by illustrations of boiling point elevation and freezing point depression as well as the determination of boiling and freezing points of a solution. Calculation of osmotic pressure and its use to determine the molar mass of a solute is discussed.

Development of Aqueous Formulation Containing the Extracted Mangiferin

Mangiferin, a polyphenol of C-glycosylxanthone, exhibits various bioactivities with poor aqueous solubility. It is known as a potent antioxidant, which leads to remarkable UV protection and anti-aging properties. Mangiferin can be found in many plant species, among which the mango leaf is one of the primary sources. From our study, the extraction yield of mangifein obtained from the leaves of Mangifera indica L. variety Nam Doc Mai was 3.17% with 95.02% ± 0.064 purity (HPTLC analysis). The solubility of mangiferin in the studied pure solvents arranging in descending order were ethoxydiglycol, dimethyl isosorbide, polyethylene glycol 400, polyethylene glycol 600, propylene glycol, dipropylene glycol, glycerin, isopentyldiol, methanol, ethanol and water, whereas the addition of the solvent in water could increase the aqueous solubility of mangiferin. In several cases, the solubility was apparently higher than that dissolved in its pure solvent state. The log-linear solubility model for the cosolvent system was used to calculate the volume fractions of the selected solvents needed to solubilize mangiferin content at the twenty times of the IC50 against DPPH radicals. In conclusion, the developed aqueous formulation contained 0.5% w/v of mangiferin and 20% w/v of polyethylene glycol 600 or dipropylene glycol as a solubilizer in water.

Cerium(III) Nitrate Containing Electrospun Wound Dressing for Mitigating Burn Severity

Thermal injuries pose a risk for service members in prolonged field care (PFC) situations or to civilians in levels of lower care. Without access to prompt surgical intervention and treatment, potentially salvageable tissues are compromised, resulting in increases in both wound size and depth. Immediate debridement of necrotic tissue enhances survivability and mitigates the risks of burn shock, multiple organ failure, and infection. However, due to the difficulty of surgical removal of the burn eschar in PFC situations and lower levels of care, it is of utmost importance to develop alternative methods for burn stabilization. Studies have indicated that cerium(III) nitrate may be used to prolong the time before surgical intervention is required. The objective of this study was to incorporate cerium(III) nitrate into an electrospun dressing that could provide burst release. Select dosages of cerium(III) nitrate were dissolved with either pure solvent or polyethylene oxide (PEO) for coaxial or traditional electrospinning set-ups, respectively. The solutions were coaxially electrospun onto a rotating mandrel, resulting in a combined nonwoven mesh, and then compared to traditionally spun solutions. Dressings were evaluated for topography, morphology, and porosity using scanning electron microscopy and helium pycnometry. Additionally, cerium(III) loading efficiency, release rates, and cytocompatibility were evaluated in both static and dynamic environments. Imaging showed randomly aligned polymer nanofibers with fiber diameters of 1161 ± 210 nm and 1090 ± 250 nm for traditionally and coaxially spun PEO/cerium(III) nitrate dressings, respectively. Assay results indicated that the electrospun dressings contained cerium(III) nitrate properties, with the coaxially spun dressings containing 33% more cerium(III) nitrate than their traditionally spun counterparts. Finally, release studies revealed that PEO-based dressings released the entirety of their contents within the first hour with no detrimental cytocompatibility effects for coaxially-spun dressings. The study herein shows the successful incorporation of cerium(III) nitrate into an electrospun dressing.

Monolayer graphene membranes for molecular separation in high-temperature harsh organic solvents

The excellent thermal and chemical stability of monolayer graphene makes it an ideal material for separations at high temperatures and in harsh organic solvents. Here, based on understanding of solvent permeation through nanoporous graphene via molecular dynamics simulation, a resistance model was established to guide the design of a defect-tolerant graphene composite membrane consisting of monolayer graphene on a porous supporting substrate. Guided by the model, we experimentally engineered polyimide (PI) supporting substrates with appropriate pore size, permeance, and excellent solvent resistance and investigated transport across the resulting graphene-covered membranes. The cross-linked PI substrate could effectively mitigate the impacts of leakage through defects across graphene to allow selective transport without defect sealing. The graphene-covered membrane showed pure solvent permeance of 24.1 L m−2 h−1 bar−1 and stable rejection (∼90%) of Allura Red AC (496.42 g mol−1) in a harsh polar solvent, dimethylformamide (DMF), at 100 °C for 10 d.

Intensification of CO2 absorption using MDEA-based nanofluid in a hollow fibre membrane contactor

Porous hollow fibres made of polyvinylidene fluoride were employed as membrane contactor for carbon dioxide (CO2) absorption in a gas–liquid mode with methyldiethanolamine (MDEA) based nanofluid absorbent. Both theoretical and experimental works were carried out in which a mechanistic model was developed that considers the mass transfer of components in all subdomains of the contactor module. Also, the model considers convectional mass transfer in shell and tube subdomains with the chemical reaction as well as Grazing and Brownian motion of nanoparticles effects. The predicted outputs of the developed model and simulations showed that the dispersion of CNT nanoparticles to MDEA-based solvent improves CO2 capture percentage compared to the pure solvent. In addition, the efficiency of CO2 capture for MDEA-based nanofluid was increased with rising MDEA content, liquid flow rate and membrane porosity. On the other hand, the enhancement of gas velocity and the membrane tortuosity led to reduced CO2 capture efficiency in the module. Moreover, it was revealed that the CNT nanoparticles effect on CO2 removal is higher in the presence of lower MDEA concentration (5%) in the solvent. The model was validated by comparing with the experimental data, and great agreement was obtained.

A Mathematical Model to Predict Solvent/Steam Flashing in Pure Solvent or Solvent/Steam Coinjection in Horizontal Producers

Summary Although the steam assisted gravity drainage (SAGD) process is still the preferred thermal-recovery process method for Athabascan deposits in Alberta, Canada, the interest in solvent-based techniques is growing due to reduce greenhouse-gas (GHG) emissions and water treatment concerns. In SAGD process, the thermodynamic trapping or subcool trapping is quite efficient due to strongly dependency of bitumen viscosity to temperature. As Irani (2018) discussed subcool trapping for solvent applications such NsolvTM recovery process is inefficient due to week dependency of solvent viscosity to temperature. Other factor that effects the efficiency of the thermodynamic trapping is that the pure solvent injection recovery processes are operated at low pressure and it is not large temperature window for operators to apply large subcools. Such challenges make the pure solvent injection recovery processes a perfect case for deployment of Flow-Control-Devices (FCDs). FCDs have demonstrated significant potential for improving recovery in SAGD production wells. FCD experience in SAGD has been primarily positive and most producers performed better with FCDs. Application of FCDs are even more important in pure-solvent injection recovery processes due to large amount of solvent in the liquid pool and also low latent heat of solvent in comparison of water. With FCDs, the draw-down pressure is typically higher, resulting in flashing near the well bore, which is largely correlated to latent heat of the main fluid in the liquid pool. The flashing creates either steam or vapour breakthrough that causes the reduction in the relative permeability of the liquid phase. Such mobility reduction creates new equilibrium that stabilizes at lower rates. Such new equilibrium analysis is conducted by forcing a new temperature gradient to the model. Such condition creates an environment that leads into extensive solvent-breakthrough called solvent-coning in this study. The main output of such analysis is the produced solvent gas-fraction produced at the sand-face. The gas-fraction is an important input for the flow control devices (FCDs) especially at subcools close to the zero, as it controls its behavior. EoS model is also created and simplified to be possible to used in defining different equilibrium conditions. This type of analysis can help the operators evaluate the effectiveness of different type of FCDs, whether they are primarily momentum- or friction-style devices for application of the pure solvent injection recovery processes. This study is the first of its kind that couple the EoS and Darcy flow in the liquid pool. The model includes all the factors into a liquid-relative-permeability, and limitation of the liquid flow into producer is modeled by Darcy flow and reduction of such relative-permeability.

Molecular Simulation of Electrode-Solution Interfaces

Many key industrial processes, from electricity production, conversion, and storage to electrocatalysis or electrochemistry in general, rely on physical mechanisms occurring at the interface between a metallic electrode and an electrolyte solution, summarized by the concept of an electric double layer, with the accumulation/depletion of electrons on the metal side and of ions on the liquid side. While electrostatic interactions play an essential role in the structure, thermodynamics, dynamics, and reactivity of electrode-electrolyte interfaces, these properties also crucially depend on the nature of the ions and solvent, as well as that of the metal itself. Such interfaces pose many challenges for modeling because they are a place where quantum chemistry meets statistical physics. In the present review, we explore the recent advances in the description and understanding of electrode-electrolyte interfaces with classical molecular simulations, with a focus on planar interfaces and solvent-based liquids, from pure solvent to water-in-salt-electrolytes. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.