Acetic Acid Aqueous Solution Research Articles

Chitosan membranes from acetic acid and imidazolium ionic liquids: Effect of imidazolium structure on membrane properties

Mixed solvent systems of an acetic acid aqueous solution with different imidazolium ionic liquids were developed for successful chitosan dissolution at room temperature, then chitosan membranes were prepared using casting method. 1-butyl-3-methyl-imidazolium acetate ([Bmim]Ac), 1-ethyl-3-methyl-imidazolium chloride ([Emim]Cl), and 1-methyl-3-(3-sulfopropyl) imidazolium zwitterion (mPSO3) were used for chitosan dissolution. Chitosan membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance characterization (1HNMR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), water contact angle, swelling degree, and tensile strength. The effect of imidazolium ionic liquid addition upon the physicochemical properties of chitosan membrane was clarified. The results indicated that chitosan could not dissolve in common imidazolium-based ionic liquid aqueous solutions, while the imidazolium ionic liquid addition positively participated in chitosan dissolution of acetic acid aqueous solutions. The results also showed that imidazolium ionic liquids reduced the crystallinity of chitosan membranes, while improved the thermal stability and strength tensile of membranes. Moreover, imidazolium ionic liquids showed different effects on crystallinity reduction, contact angles, and swelling degree. It is possible of tuning the physicochemical properties of chitosan membranes by adding different imidazolium ionic liquids during aqueous acetic acid dissolution. The information obtained will shed light on the optimization of novel solvent systems for fast and rapid chitosan dissolution.

Report of the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) on the safe use of two aqueous solutions of hydrogen peroxide, acetic acid and peracetic acid as processing aids for the bacterial disinfection of apples and peaches washing water

Report of the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) on the safe use of two aqueous solutions of hydrogen peroxide, acetic acid and peracetic acid as processing aids for the bacterial disinfection of apples and peaches washing water

A novel comparative chromatographic research of secoiridoid glycosides in two species of centaury herb

The aim: A novel comparative analysis of the secoiridoid glycosides composition in Centaurium erythraea Rafn. and Cеntaurium pulchellum (Sw.) Druce has being described. Swertiamarin has been chosen as an active marker and its comparative quantitative estimation in two species of the raw material has been carried out by HPLC method.
 Materials and methods: The quantitative HPLC analysis of swertiamarin was conducted using a chromatographic column ACE 5 C18. Methanol and 0,5 % acetic acid aqueous solution were used as mobile phases; the chromatographic procedure was carried out in a gradient mode.
 Results: The content of swertiamarin in the C. pulchellum herb ranges from 2.51 to 3.07 mg/100 mg. In that time swertiamarin content in C. erythraea herb varies and depends from 3.83 to 8.94 mg/100 mg. The content of swertiamarin in C. pulchellum herb is much lower than in C. erythraea herb. Taking into account this fact the possibility of using of C. pulchellum herb for medicine instead of C. erythraea herb must be proven additionally by biological experiments. Also it could be preliminary concluded that the most appropriate climate for swertiamarin accumulation in C. erythraea herb is located in Central and Eastern parts of Ukraine.
 Conclusions: It was discovered that the main representative of secoiridoid glycosides in C. erythraea is swertiamarin when in C. pulchellum Druce that are represented by both sweroside and swertiamarin. A more perspective raw material – C. erythraea herb, according to the content of swertiamarin, was chosen

EFFECT OF PHYSICOCHEMICAL PROPERTIES OF d-METAL OXIDES ON SUNFLOWER OIL TRANSESTERIFICATION

The physicochemical indicators of d-metal oxides (NiO, CuO, MnO, FeO, PbO, ZnO) which are heterogeneous catalysts for the transesterification process of sunflower oil triglycerides by ethanol and butan-1-ol have been determined. The available specific surface area, surface acidity and basicity, as well as the hydrogen potential change of the catalyst suspension in water were determined for the oxides. The available specific surface area of the oxides was determined by titration of their aqueous suspension with a solution of methylene blue with a predetermined concentration. The surface acidity and basicity of the catalysts were determined by back titration of samples treated with an aqueous solution of ammonia and acetic acid, respectively. It was found that all investigated d-metal oxides have a low specific surface area. The value of specific surface area is in the range of 0.6-1.5 m2/g. The surface acidity and basicity of the catalysts is 0.13-0.27 mmol/g and 0.019-0.066 mmol/g, respectively. It is shown that the change in the aqueous suspension hydrogen potential of the investigated catalysts relative to the distilled water pH is maximum for NiO and ZnO and it is 0.6-0.65, while for CuO this change is the smallest and it is only 0.3. The character of the pH change curves and the pH values of the oxides suspension in equilibrium condition indicate the presence of weak acid sites in the studied catalysts. The indicated catalysts characteristics are compared with the results obtained in the transesterification process of sunflower oil triglycerides by ethanol and butan-1-ol. It was found that there is a correlation between the surface acidity of catalyst and the reaction initial rate of triglycerides transesterification by ethanol and butan-1-ol. At the same time, such a correlation is absent for the surface basicity of the catalysts. This is consistent with the data on the catalysis of the triglyceride transesterification reaction only by strong major active sites. It is concluded that the transesterification reaction of sunflower oil triglycerides by ethanol and butan-1-ol occurs predominantly on the weak acid centers of the d-metal oxides.

Quantitation and content investigation of bilirubin in cultured cow-bezoar

A determination method for bilirubin in cultured cow-bezoar was developed in this study, with which the bilirubin in 15 batches of samples was quantified. The samples were first processed with 10% oxalic acid solution for the conversion of bilirubin from conjugated to unconjugated, followed by the extraction with dichloromethane. Then the obtained sample solutions were analyzed at 450 nm by HPLC[chromatographic column: Agilent TC-C_(18)(4.6 mm × 250 mm, 5 μm); mobile phase: acetonitrile and 1% glacial acetic acid aqueous solution(95∶5); flow rate: 1.0 mL·min~(-1)]. The bilirubin content in the 15 batches of cultured cow-bezoar was ranged from 21.9% to 41.7% with the average of 32.4%. The proposed method is accurate and reliable, thus making it suitable for the quantitation of bilirubin in cultured cow-bezoar and its quality assessment and control.

Chitosan and Aloe vera gel formulations as wound healing agents in episiotomy

Episiotomy is an obstetric technique that consists of making an incision in the perineum during vaginal childbirth, to facilitate the baby to pass through. After delivery, the perineal region is sutured with absorbable threads to heal the cut. However, are frequent reports of pain, infections, and dyspareunia after the execution of this technique. In this context, the use of biomaterials becomes relevant as they promote faster and safer tissue repair, making it an attractive alternative for the healing process of episiotomy. Based on the physical-chemical and biological properties of chitosan and Aloe vera, this research developed three different vaginal gels, with the purpose of promoting tissue regeneration and infection prevention post-episiotomy. Chitosan solutions with concentrations of 5% w/v were prepared by dissolving the chitosan powder in 2% v/v aqueous solution of acetic acid. After the extraction and processing of the mucilage, the pulp of the Aloe vera leaf was added to the chitosan gel in the proportions of 1, 2, and 3% v/v. All formulations were neutralized by the slow drip technique of a neutralizing solution of sodium hydroxide (2 M). The compositions were analyzed according to their organoleptic aspect, optical microscopy, spreadability, hydrogen potential, absorption spectroscopy, cytotoxicity, and rheological behavior. Based on the results obtained, it was possible to conclude that gels produced have the potential to be used as vaginal gels.

Improvement of Extractive Alkylation Gas Chromatography of Short-chain Carboxylic Acids in Aqueous Solution.

In the analysis of short-chain carboxylic acids such as formic acid and acetic acid in aqueous solution using extractive alkylation gas chromatography, tetrahexylammonium bromide (THAB) as a phase-transfer catalyst (PTC) causes a high intensity and broad peaks in the gas chromatogram, and interfere with the detection of carboxylic acid derivatives. By an easy treatment of the extractive alkylation solution with perchloric acid and n-hexane, it is possible to remove more than 95% of THAB, and to provide good gas chromatogram with a little admixture of carboxylic acid derivatives. The desensitization was 16% at the maximum, the contamination of the glass insert in gas chromatograph and liquid phase in column by THAB was minimized, and trouble in continuous measurement could be avoided.

Synthesis, characterization and application of spherical and uniform molecularly imprinted polymeric nanobeads as efficient sorbent for selective extraction of rosmarinic acid from plant matrix

This work reports the synthesis and application of uniform and spherical molecularly imprinted polymeric (MIP) nanobeads for selective and efficient preconcentration of Rosmarinic acid (RA). The as-prepared RA MIP nanobeads were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) techniques. As analyzed, nano-sized particles of MIP with spherical and uniform shape and the average size of 88 nm were synthesized. The prepared MIP nanobeads were used in an ultrasonic-assisted dispersive solid phase extraction approach (UA-DSPE) for extraction of RA as a natural antioxidant specie from the extract of Salvia Officinalis leaves. In UA-DSPE process, the RA content of the samples was determined using high-performance liquid chromatography (HPLC). The highest recovery percentage (>90%) was observed after loading of RA solution (pH 5.7) and after elution with 3 mL of acetic acid aqueous solution, followed by 6 min sonication. The selectivity studies demonstrated a selective and high affinity binding of the template molecule (i.e. RA) toward MIP sorbent compared to other compounds such as gallic acid, caffeic acid, and pyrocatechol.

Bio-inspired construction of ion conductive pathway in covalent organic framework membranes for efficient lithium extraction

Summary As the most sophisticated separation system, biological membranes have served as natural prototypes for the design of artificial membranes because they provide high permeability and solute selectivity, owing to the presence of specialized ion channels. However, developing stable and selective artificial ion channels remains a formidable challenge. Herein, we demonstrate the construction of lithium nanochannels in two-dimensional covalent organic frameworks (COFs) to create biomimetic membranes. Implanted lithiophilic oligoethers conferred specificity and facilitated Li+ diffusion along the pore pathway of the COF. The ion channel characteristics were indicated by reversal potential measurements, showing that the relative permeability decreased in the order Li+ > K+ > Na+ > Ca2+ > Mg2+. The Li+ transfer was enhanced, while other ions were obstructed, allowing for high selectivity and permeability. A Li+/Mg2+ separation factor of 64 was achieved, confirming high lithium affinity. This study may serve as a design principle to develop selective artificial membranes for effective ion separation.

Tailored organosolv banana peels lignins: Improved thermal, antioxidant and antimicrobial performances by controlling process parameters

There is a growing environmental concern in the world for replacing the traditional petroleum-based products. The aim of this work was to evaluate the structure – property relationship of banana peel lignins (BPLs) as antioxidant and antimicrobial agents by controlling the parameters of organosolv process. The milled banana peel was hydrolyzed using an aqueous acetic acid solution (70, 80 and 90% v/v) and 2.0% v/v HCl at 110 °C for 1, 2 and 3 h. BPLs were characterized by FTIR, 1H NMR, 1H13C HSQC, 31P NMR, GPC and TGA. The antioxidant capacity of BPLs was evaluated by DPPH, ABTS and H2O2 assays, comparing their performance with that of ascorbic and gallic acid. The antimicrobial activity of BPLs was evaluated against E. coli. The reaction time and acetic acid/water ratio had significant effects on the yield and purity of BPLs. The composition of organosolv solution also affected their total amount of hydroxyls (0.71–0.82 mmol g−1), Mw (2759–3954 g mol−1), Tonset (232–254 °C), antioxidant and antimicrobial activities. It can be concluded that the control of organosolv parameters can be a useful tool for tuning the structural features of lignins and to maximize their performance.

Electrophoretic Determination of Symmetric and Asymmetric Dimethylarginine in Human Blood Plasma with Whole Capillary Sample Injection.

Asymmetric and symmetric dimethylarginines are toxic non-coded amino acids. They are formed by post-translational modifications and play multifunctional roles in some human diseases. Their determination in human blood plasma is performed using capillary electrophoresis with contactless conductivity detection. The separations are performed in a capillary covered with covalently bonded PAMAPTAC polymer, which generates anionic electroosmotic flow and the separation takes place in the counter-current regime. The background electrolyte is a 750 mM aqueous solution of acetic acid with pH 2.45. The plasma samples for analysis are treated by the addition of acetonitrile and injected into the capillary in a large volume, reaching 94.5% of the total volume of the capillary, and subsequently subjected to electrophoretic stacking. The attained LODs are 16 nm for ADMA and 22 nM for SDMA. The electrophoretic resolution of both isomers has a value of 5.3. The developed method is sufficiently sensitive for the determination of plasmatic levels of ADMA and SDMA. The determination does not require derivatization and the individual steps in the electrophoretic stacking are fully automated. The determined plasmatic levels for healthy individuals vary in the range 0.36–0.62 µM for ADMA and 0.32–0.70 µM for SDMA.

High Energy Density Rechargeable Aqueous Lithium Batteries with an Aqueous Hydroquinone Sulfonic Acid and Benzoquinone Sulfonic Acid Redox Couple Cathode

The demand for high energy density rechargeable batteries beyond lithium-ion batteries has increased for electric vehicles. In the present study, a novel high energy density rechargeable aqueous lithium battery was proposed. The battery was composed of a lithium metal anode, a lithium-stable non-aqueous electrolyte, a water-stable lithium-ion conducting solid electrolyte of Li1.4Al0.4Ge0.2Ti1.4(PO4)3-epoxy-TiO2 separator, and a hydroquinone sulfonic acid (HQS)/benzoquinone sulfonic acid (BQS) redox couple in an aqueous acetic acid solution (HAc). An open-circuit voltage of 3.7 V at 25 °C was recorded, and the theoretical energy density of the battery based on the reaction 2Li + BQS + 2H2O = 2 LiOH + HQS was 833 Whkg-1, about two times higher than that of the lithium-ion battery. The battery was successfully cycled at 0.5 mA cm-2 and 25 °C with low polarization.

Efficient preparation of caffeoylquinic acids from the flowers of Artemisia anomala by supramolecular solvent/equilibrium solution extraction followed by re-extraction

In this study, the potential of supramolecular solvent/equilibrium solution (SUPRAS/EqS) for the extraction of caffeoylquinic acids from the flowers of Artemisia anomala (AAF) coupled with re-extraction was evaluated. Extraction and re-extraction parameters were optimized based on the yield of 3-chlorogenic acid, isochlorogenic acid A-C. The DPPH radical scavenging and xanthine oxidase inhibitory activity of the final extracts were also evaluated. SUPRAS/EqS, made up by n-octanoic acid, ethanol, 5% acetic acid aqueous solution, offered advantages in terms of rapidity (extraction for 1 min) and simplicity (the process involved vortex-shaken and centrifugation at room temperature), thus avoiding cost processes based on high pressure or temperature. Multi-stage countercurrent extraction (MSCE) procedure was successfully applied to reduce the consumption of extraction solvent (24-fold volume of raw materials in total). SUPRAS/EqS-MSCE extracts were evaporated to recycle ethanol and then re-extracted by water for 3 times (with a total consumption of 9-fold volume of material weight). The contents of 3-chlorogenic acid, isochlorogenic acid B, isochlorogenic acid A, isochlorogenic acid C in the final extract were 3.61 ± 0.01, 2.32 ± 0.01, 26.42 ± 0.05, 5.38 ± 0.01 mg/g dry weight of AAF with a recovery rate of 95.0%, 92.7%, 90.6% and 94.5%, respectively. Furthermore, the final extract of AAF exhibited moderate DPPH radical scavenging activity (IC50 value was 839. 46 ± 1.02 μg/mL, vitamin C’s was 220.29 ± 1.02 μg/mL) and weak xanthine oxidase inhibitory activity (IC50 value was 4518.56 ± 1.03 μg/mL, quercetin’s was 103.04 ± 1.04 μg/mL).

Quantitative Determination of 7 Saikosaponins in Xiaochaihu Granules Using High-Performance Liquid Chromatography with Charged Aerosol Detection.

Bupleuri Radix (Chaihu, in Chinese) is the principal drug in Xiaochaihu granules (XGs) that is a famous Chinese medicine preparation in China. Since previous analytical methods have not focused on the multiactive saikosaponins of Chaihu, it is difficult to effectively control the quality of XG on the market. In this manuscript, the simultaneous determination of 7 saikosaponins (saikosaponins C, I, H, A, B2, G, and B1) in XG by HPLC with charged aerosol detection (CAD) and confirmation by LC-Q-Orbitrap HRMS were described. The saikosaponins were purified on an SPE cartridge and determined on a Waters CORTECTS C18 column (4.6 mm × 150 mm, 2.7 μm) by gradient elution using 0.01% acetic acid aqueous solution and acetonitrile. The results showed good linearity with the r2 values higher than 0.998 for all analytes. The average recoveries at three different concentration levels ranged from 80% to 109% and the intraday and interday precision (relative standard deviations, RSD%) were in the range of 1.0%∼1.9% and 1.4%∼2.1%, respectively. The established HPLC-CAD method was subsequently applied to 15 batches of XG to investigate the batch-to-batch consistency and controllability. The proposed method could potentially be used for the quality control of XG and also be helpful in the quality evaluation of Chaihu and its related preparations.

Development of a Simple and Sensitive Pre-column Derivatization HPLC Method for the Quantitative Analysis of Miglitol Intermediates

In the synthesis of hypoglycemic agent miglitol, the quantitative analysis of two key intermediates, N-2-hydroxyethyl glucamine and 6-(N-hydroxyethyl)-amino-6-deoxy-alpha-L-sorbofuranose, has long been a challenge. In this study, derivatization reagents were screened, and then a novel HPLC method coupled with 9-fluorenylmethyl chloroformate derivatization was developed for the quantitative analysis of the two miglitol intermediates. The derivatization was performed by reacting Fmoc-Cl and the intermediates at a molar ratio of 16:1 and sodium borate at a final concentration of 0.2 mol/L at pH 8.0, 35 °C for 40 min, followed by the addition of 1.5 times the volume of acetic acid (0.1%, w/v). The analysis was achieved on Hypersil ODS2 (4.6 mm × 250 mm) column applying an isocratic mobile phase containing acetonitrile and 0.1% acetic acid aqueous solution (45:55, v/v) at 0.8 mL/min flow rate and an injection volume of 10 μL. The analyte was detected at 254 nm. The method showed good linearity, precision, and accuracy. It was capable of detecting both intermediates at low concentrations. Interestingly, we found that a small amount (> 5%) of N-2-hydroxyethyl glucamine was not converted to 6-(N-hydroxyethyl)-amino-6-deoxy-alpha-L-sorbofuranose in the biotransformation. This method was reliable and efficient for the analysis of miglitol intermediates.

Dehydration of a Dilute Acetic Acid‐Water Mixture via Batch Heteroazeotropic Distillation

AbstractDehydration via batch heteroazeotropic distillation emerges as a promising technology for the recovery of acetic acid (HAc) from dilute aqueous solutions. In this preliminary work, this process was studied with the aid of Aspen Batch Modeler®, using an acetic acid aqueous solution as the model feed instead of wood vinegar from biorefineries andn‐butyl acetate as the azeotropic entrainer. The non‐random two liquids (NRTL)‐virial Hayden‐O'Connell model (HOC) model was chosen to calculate the thermodynamic properties. The response surface methodology with Box‐Behnken design was successfully applied to obtain optimum process conditions, providing a dehydrated HAc product from the pot with high purity and recovery.

Investigation of the possibility of using coagulant for cleaning used motor oils

The article is devoted to studying the possibility of using organic or inorganic coagulants in the process of purification of used motor oils (UMO). In experimental studies, combinations of aqueous solution of carbomide, acetic acid and isopropyl alcohol were used as coagulants. The analysis showed that the third variant of coagulant combination was the most effective. Mathematical models were obtained. Varying factors: percentage of coagulant α (%), settling temperature t (°C) and settling time τ (min−1). The mathematical model is constructed for response functions: alkaline pH number, oil color (OC) of mechanical impurities content (β). The research results showed that this coagulant improves the color of used oil. The use of this coagulant increases the alkaline number of purified oil. It reduces the content of mechanical impurities.

Influence of the Ni-Co/Al-Mg Catalyst Loading in the Continuous Aqueous Phase Reforming of the Bio-Oil Aqueous Fraction

The effect of catalyst loading in the Aqueous Phase Reforming (APR) of bio-oil aqueous fraction has been studied with a Ni-Co/Al-Mg coprecipitated catalyst. Because of the high content of water in the bio-oil aqueous fraction, APR could be a useful process to convert this fraction into valuable products. Experiments of APR with continuous feeding of aqueous solution of acetol, butanol and acetic acid as the only compound, together with a simulated and a real aqueous fraction of bio-oil, were carried out. Liquid products in the liquid effluent of the APR model compounds were quantified and the reaction pathways were revised. The increase of catalyst loading produced an increase of gas production and a gas with higher alkanes content. Acetol was the compound with the highest reactivity while the conversion of acetic acid was very low. The presence of acetic acid in the feed caused catalyst deactivation.

Chromatographic Estimation of Water Soluble Vitamins in Wild Edible Plants

A reversed-phase high performance liquid chromatographic technique has been developed for the simultaneous quantitation of water soluble vitamins in 10 potent wild edible plants consumed by the tribal people of North-eastern region in India. The chromatographic separations of vitamins were assessed on Acclaim C18 column using a mobile phase of acetonitrile and aqueous trifluoro acetic acid solution with gradient elution. The experimental results exhibited that for different plants, the vitamin C content ranged between 0.15 ± 0.003 to 8.10 ± 0.03 mg/100g dry plant material (DPM). The vitamin B2 content was determined high in C. album (2.64 ± 0.03 mg/100g DPM) and significant amount of vitamin B9 (1.44 ± 0.03 mg/100g) was detected in E. acuminata. The results showed that these plants are rich sources of vitamins, which can contribute immensely to nutrition and food security. The high percentage of recovery and low limit of detection confirm the suitability of the method for simultaneous estimation of vitamins in these 10 wild edible plants.

Gas Transmission Rates of Mango (Mangifera indica L. ‘Carabao’) Peel as Affected by Chitosan-Nanosilica Composite Fruit Coating

Direct measurement of gas transmission rates of coated commodity under controlled environmental conditions is needed in formulating coatings to extend shelf life of fruits. The gas transmission rate of coated commodities, along with its respiration rate can be used to predict the level of modification of internal atmosphere and the quality of the product during storage. Oxygen (O2) and carbon dioxide (CO2) transmission rates of mango (Mangifera indica L. cv Carabao) peel coated with different formulations of chitosan-nanosilica at three storage temperatures were estimated using Exponential Decay Method. The coating was prepared by dissolving chitosan (CS) in aqueous solution of glacial acetic acid (0.25% v/v) and blending with nanosilica (NS) dispersion. The resulting films have microcracks and agglomeration of NS throughout the surface. 0.75% CS at 25°C had the highest gas transmission rate (1.136 mLO2 cm-2 h -1 and 3.243 mLCO2 cm-2 h -1 ) whereas 1% CS+ 0.03% NS at 15°C had the lowest gas transmission rate (0.406 mLO2 cm-2 h -1 and 1.586 mLCO2 cm-2 h -1 ). At constant temperature, increasing chitosan concentration decreases O2 and CO2 transmission rates by almost 44% and 41%, respectively, whereas the incorporation of NS decreases the O2 transmission rate by 10% to 20% and CO2 transmission rate by 5% to 14%. Gas transmission rates were highest at 25°C and lowest at 15°C