Acetic Acid Aqueous Solution Research Articles

High-performance liquid chromatography (HPLC) analysis for flavonoids profiling of Napier grass herbal tea

Natural plant products are becoming more and more essential in helping to promote safe well-being worldwide. This leads to a substantial rise in the consumption of various herbal teas. The presence of beneficial bioactive ingredients such as flavonoids may be correlated with Napier grass herbal tea having health benefits associated with their intake. Studies have shown that herbal teas have preferentially high antioxidant activity due to the presence of flavonoids in them. The purpose of this study was to identify the Napier grass herbal teas flavonoids prepared under different conditions. Napier grass herbal teas have been formulated using green tea and black tea processes, respectively. The tea samples were extracted in water (95°C, 30 mins) and 60% (v/v) aqueous methanol (30 mins), respectively. Approximately, 1% (v/v) aqueous acetic acid solution (solvent A) and acetonitrile (solvent B) were used as the mobile phase. The flow rate was adjusted to 0.7 mL/min, the column was thermostatically controlled at 28°C, and the injection column was kept at 20 μL. HPLC chromatograms were detected using a photodiode array UV detector at 272 nm. Gallic acid, P-coumaric acid, catechin, epigallocatechin gallate, quercetin, rutin, myricetin and kaempferol were found in both Napier grass water and methanolic extracts, respectively. The findings suggested that the HPLC techniques are ideal for the detection and identification of flavonoids in Napier grass teas

EFFECT OF CATALYSTS ON THE YIELD AND PROPERTIES OF LIGNIN FROM MICROWAVEASSISTED ACETOSOLV EXTRACTION OF OIL PALM EMPTY FRUIT BUNCH FIBRES

cetosolv is an enhancement organosolv technique utilising acetic acid as solvent and produces high purity of lignin. However, the limitation of this technique in the conventional heating method is the high energy consumption during a long reaction time. Therefore, the employment of microwave is used to overcome this limitation with the expectation of a lower power consumption and short reaction time. In this study, three types of catalysts, sulphuric acid (H2SO4), aluminium choride (AlCl3), and chromium nitrate [Cr(NO3)3] were used to investigate the lignin extraction performance and its properties from microwave-assisted acetosolv (MWA) treatment of oil palm empty fruit bunches (EFB). The highest yields of lignin (76.98%) were obtained using an aqueous solution of acetic acid combined with 3.0% of H2SO4 under 110°C for 30 min. Meanwhile, AlCl3 performed almost similar to H2SO4, providing lignin yield of 71.57% at the highest temperature of 110°C. The usage of microwave-assisted technique also produces a high yield and high purity of lignin. It is also proven that AlCl3 can be a substitute to Bronsted acid for lignin extraction. However, Cr(NO3)3 was found not suitable for the lignin’s extraction despite having a high potential for cellulose extraction.

Carboxylic acid recovery from Fischer\u2013Tropsch aqueous product by fractional freezing

About half of the product from iron-based high-temperature Fischer–Tropsch synthesis is an aqueous product containing dissolved oxygenates. Volatile oxygenates can be recovered by distillation, but the bulk of the carboxylic acids remain in the water, which is called acid water. Fractional freezing was explored as a process for producing a more concentrated carboxylic acid solution from which the carboxylic acids could be recovered as petrochemical products, while concomitantly producing a cleaner wastewater. Solid–liquid equilibrium data were collected for aqueous solutions of acetic acid, propionic acid, and butyric acid. A synthetic Fischer–Tropsch acid water mixture (0.70 wt% acetic acid, 0.15 wt% propionic acid, and 0.15 wt% butyric acid) was prepared and the liquid phase concentrations of the acid species at solid–liquid equilibrium were determined. Control experiments with material balance closure on each of the carboxylic acid species were performed at selected conditions. Having more than one carboxylic acid species present in the mixture meaningfully changed the solid–liquid equilibrium versus temperature of the system. The carboxylic acids partitioned between the solid phase and the liquid phase and a practical design would require multiple duty-controlled solid–liquid equilibrium stages, with most of the separation taking place in the temperature range 0 to − 5 °C.

A density functional theory study on the structure formation of Al(III) carboxylate complexes in aqueous aluminum sols

AbstractIn‐depth studies of the structure of precursor sols is very important for understanding the subsequent sol to gel transition. Here, density functional theory was applied to study the reaction of Al powder with formic and acetic acid in aqueous solution to find the structure of Al(III) complex in precursor sols. The Al3+ ion obtained by dissolving Al powder in aqueous solution of formic and acetic acid would preferentially coordinate with water molecules to form aluminum hydrates. As the reaction energy barrier of aluminum hydrates with CH3COO− and HCOO− was comparable, both aluminum formoacetate and other aluminum carboxylate monomers could be obtained. Most Al(III) complexes formed by other carboxylate monomers were similar to that prepared from aluminum formoacetate. However, some Al(III) monomers and Al(III) dimer with different structural characteristics might be detrimental to the formation of linear polymers. The formation of other aluminum carboxylate monomers had great influence on the structure of precursor sols.

Exfoliated graphite preparation based on an eco-friendly mechanochemical route

In the present study, we proposed an eco-friendly method to produce exfoliated graphite based on a dry mechanochemical process. This route represents an alternative that avoids the use and disposal problems related to highly corrosive and dangerous reagents use, manipulation and elimination. As non-toxic alternative exfoliation route, an equimolar mixture of graphite flakes and calcium carbonate was milled and leached with an aqueous solution of acetic acid (vinegar). There was a notable reduction of the graphite particle size with a significantly increased level of exfoliation, which dramatically improved the surface area of the prepared samples from 4 to 363 m2 g-1. After 16 h of processing, milled particles reached a thickness reduction of up to 5 nm and micrometric widths.The overall yield of processed graphite is around 92% based on the raw graphite. The evident benefits of the obtained exfoliated graphites in the adsorption of methylene blue (a common pollutant of textile wastewater) are presented. Exfoliated graphite represents a valid alternative as adsorption agent for dye removal reaching efficiencies above 95% after 30 min of testing with an aqueous solution of methylene blue. Contrary, the untreated graphite sample showed a null adsorption activity.

Aqueous solutions ofglycolic, propionic, or lactic acid in substitution of acetic acid to prepare chitosan dispersions: a study based on rheological and physicochemical properties.

Chitosan (CH) is a biopolymer derived from chitin, which is the second most abundant polysaccharide in nature, after cellulose. Their functional groups -NH2 and -OH can form intermolecular interactions with water and other molecules, enabling a variety of applications for CH. -NH2 groups become protonated in acidic solutions, causing an increase in electrostatic repulsion between CH chains, which facilitates their dispersionin aqueous media. Aqueous solutions ofacetic acid and/or acetates buffers have been used to disperse CH, but may not be adequate for technological applications, espeacially because of the strong flavor this acid confers to formulations. In this study, 0.125; 0.250; 0.500; 0.750 and 1.000g(100g)-1 CH dispersions were prepared in acidic aqueous media (50mmolL-1), not only withacetic (AA), but also withglycolic (GA), propionic (PA), or lactic (LA), acid aiming to evaluate the effects of biopolymer concentration and type of organic acid on: electrical conductivity, pH, density and rheological characteristics of dispersions. Moreover, ζ potential values of CH chains dispersed in these acidic aqueous media were assessed. pH, density and consistency index were influenced by the biopolymer concentration, butnot by the acid type. At a given biopolymer concentration, ζ potential signs (+) and values suggested that electrostatic interactions between CH chains and counter-anions occurred, regardless of the type of the organic acid. Thus, at least from a physicochemical point of view,GA, PA or LA showed to be suitable to replace AA when preparingdispersions containing from 0.125 to 1.000g(100g)-1 CH for technological purposes, such asthickening or stabilizerin formulatedfood products.

Simultaneous Quantitation of Caffeine, Ethoxybenzamide and Propyphenazone in Oral Analgesic Tablets by High-Pressure Liquid Chromatography

A method for simultaneous quantitation of caffeine, ethoxybenzamide and propyphenazone is described. The method was based on reversed-phase high-pressure liquid chromatography with a mobile phase of methanol-acetonitrile-3% aqueous acetic acid solution (24 : 16 : 60, v/v). The compounds were well separated from each other by the procedure, using salicylamide as internal standard. The method gave excellent results and provided a simple, rapid and accurate method for separation and quantitation of synthetic mixtures and commercial products.

Report of the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) on the safe use of three aqueous solutions of hydrogen peroxide, acetic acid and peracetic acid as processing aids for the bacterial disinfection of citrus fruit and pepper washing water at processing plants

Report of the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) on the safe use of three aqueous solutions of hydrogen peroxide, acetic acid and peracetic acid as processing aids for the bacterial disinfection of citrus fruit and pepper washing water at processing plants

Microwave synthesis of high-quality mordenite membrane by a two-stage varying heating-rate procedure

High performance mordenite membranes were successfully prepared on porous α-Al2O3 tubes by a novel two-stage varying heating-rate procedure under microwave assisted heating. The effect of heating rate on microstructure and performance of mordenite membrane was first time to be investigated. It was found that slowing down the heating rate at lower temperature range can improve the nucleation process, and further enhance compactness as well as performance of mordenite membrane. Crystallization time was also optimized for the preparation of high-quality mordenite membrane and it was reduced to only 75 min in this work. The as-synthesized M14 exhibits an excellent PV performance for dehydration of 90 wt% acetic acid/water mixture at 75 °C with a flux of 1.48 kg m−2 h−1 and a separation factor of larger than 10,000, which shows an excellent potential for dehydration of acetic acid aqueous solutions in industrial separation applications. Our work also provides a new idea for regulating microstructure and performance of zeolite membrane.

Determination of 42 mycotoxins in oats using a mechanically assisted QuEChERS sample preparation and UHPLC-MS/MS detection

A method was developed and validated for the simultaneous determination of 42 mycotoxins in oats. The method includes all the mycotoxins listed under Commission Regulation 1881/2006 and Commission Recommendation 165/2013, the emerging mycotoxins (beauvericin, alternariol, alternariol-methyl-ether and enniatins), and two masked metabolites, namely deoxynivalenol-3-glucoside and T-2-glucoside. The method also focuses on a wide range of analytes of toxicological interest. The sample preparation involved extraction with an aqueous acetic acid solution and acetonitrile, followed by QuEChERS with mechanically assisted vibrational shaking. No further clean-up steps were employed, and analysis was performed using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Trueness ranged between 78% and 158%, while precision ranged from 1.7% to 49.9% under within-laboratory reproducibility conditions. Beside the high degree of accuracy and sample throughput provided, the method can be applied to a large number of compounds currently not regulated, thus generating knowledge and for risk assessment purposes.

The Effect of the Nature of a Coagulant on the Nanofiltration Properties of Cellulose Membranes Formed from Solutions in Ionic Media

The effect of the nature of a coagulant on the nanofiltration characteristics of the cellulose membranes obtained from solutions in 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) or a mixture of this ionic liquid with dimethylsulfoxide (DMSO) is studied in this work. Precipitation in water leads to the formation of the densest cellulose membrane characterized by the low permeability of dimethylformamide (PDMF = 0.25 kg m−2 h−1 atm−1) and high rejection coefficients of the model substances, Orange II (350 g/mol) and Remazol Brilliant Blue R (626 g/mol), of 65 and 82%, respectively. To reduce the rate of precipitation of cellulose for the purpose of decreasing the density of the membranes, various compounds that partially mimic the medium of the solvent are introduced to water to obtain their 30% solutions: acetic acid to increase the concentration of acetate anions, N-methylmorpholine N-oxide to increase the concentration of ammonium fragments, and DMSO. In all the cases, the modification of the coagulant leads to a 2–2.5-fold increase in the permeability of the membranes without sacrificing the high values of the rejection coefficients. A cellulose membrane obtained by precipitation in a 30% aqueous solution of acetic acid demonstrates the best nanofiltration characteristics, namely, PDMF = 0.67 kg m−2 h−1 atm−1, ROrangeII = 66%, and RRemazol = 78%.

A Rat Model of Oral Mucositis Induced by Cancer Chemotherapy for Quantitative Experiments.

Oral mucositis, which occurs frequently in the treatment of cancer, is a major problem. In this study, we aimed to develop a rat model of oral mucositis induced by cancer chemotherapy for quantitative measurement. A model animal of oral mucositis was prepared by injecting an acetic acid aqueous solution into the buccal mucosa of rats to which a 5-FU solution had been previously administered. The doses of 5-FU and acetic acid were examined, and a treatment experiment using Kenalog® was performed. The optimal dose of the 5-FU solution and the optimal concentration of the acetic acid aqueous solution were 40 mg/kg and 25%, respectively. Treatment with Kenalog® confirmed that this model mimics immunocompromised oral mucositis. Compared with a mouse model, oral mucositis can be easily observed in this model and provides a large amount of oral mucosal tissue.

Separation of anaesthetic ketamine and its derivates in PAMAPTAC coated capillaries with tuneable counter-current electroosmotic flow

Capillary electrophoretic separation of ketamine, norketamine, hydroxynorketamine, and dehydronorketamine was performed in the counter-current regime under the influence of oppositely-directed electroosmotic flow. For this purpose, the fused silica capillaries were covalently coated with the poly(acrylamide-co-3-acrylamidopropyl trimethylammonium chloride) copolymer (PAMAPTAC). The content of the cationic monomer APTAC in the polymerization mixture varied in the range 0–6 mol. % and the generated electroosmotic flow increased continuously in the 0–20 · 10−9 m2V−1s−1 interval. Importantly, it resulted in improved electrophoretic resolution of ketamine/norketamine, which increased from 0.8 for neutral PAM coating (i.e. 0% PAMAPTAC) to 3.0 for 6% PAMAPTAC. The determination of ketamine and its derivates in rat serum was performed in a 4% PAMAPTAC capillary with an inner diameter of 25 μm. The separation was performed in a 500 mM aqueous solution of acetic acid (pH 2.3). The clinical sample was deproteinized by the addition of acetonitrile to the serum and a large volume of the treated sample was injected directly into the capillary. The achieved limit of detection ranged from 2.2 ng/mL for dehydronorketamine to 4.1 ng/mL for hydroxynorketamine; the intra-day repeatability was 1.0–1.5% for the migration time and 2.8–3.3% for the peak area. The developed methodology was employed for time monitoring of ketamines in rat serum after intra venous administration of low doses of anaesthetic at a level of 2 μg per g of body weight.

Corrosion mechanism analysis of the front-side metallization of a crystalline silicon PV module by a high-temperature and high-humidity test

The failure of photovoltaic modules in high-temperature and high-humidity tests is generally caused by the loss of electrical contact between the cell emitter and finger metallization, due to the corrosion of the glass layer by the acetic acid which is generated by the hydrolysis of the ethylene vinyl-acetate copolymer that is used as the encapsulant. In this study, a high-temperature high-humidity test was conducted on a photovoltaic module—namely, a solar cell with reduced output—to examine the metallization–Si wafer interface. The results confirmed that Pb was eluted from the glass layer to form an alteration layer that inhibits electron movement from the emitter layer to the metallization, thereby decreasing the output of the module. The corrosion products generated from the eluted Pb indicated that the front-side metallization was statically exposed to the same environment inside the PV module as that in an aqueous solution of acetic acid.

Green synthesis and possible applications of MoO2 nanoparticles

This work reports the green hydrothermal synthesis of MoO2 nanoparticles and their applications in Cr6+ adsorbent and MoO3 precursor. A green hydrothermal method, which was based on the autoclave-sealed reactions of (NH4)6Mo7O24•4H2O and glucose in acetic acid (12.5 vol%) aqueous solution at 190 °C for 12 hours, was proposed for the synthesis of MoO2 nanoparticles. The characterization results from X-ray diffraction and transmission electron microscopy suggested the successful preparation of pure monoclinic phase MoO2 (m-MoO2) nanoparticles. The m-MoO2 nanoparticles exhibited a good adsorption capacity for Cr6+ (for example, 300 mg of m-MoO2 nanoparticles can adsorb the whole Cr6+ in 300 mL of 50 mg/L K2Cr2O7 aqueous solution after mixing for 280 minutes). Besides, the m-MoO2 nanoparticles can be completely converted to orthorhombic phase MoO3 nanoflakes after heating in air at 400 °C for 5 hours.

Report of the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) on the safe use of an aqueous solution of hydrogen peroxide, acetic acid and peracetic acid (23/17/15) as a processing aid for the bacterial disinfection of the washing water used for cut carrots and lettuces, peeled garlic, sweet potatoes, persimmons, mangoes and avocados in processing

Report of the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) on the safe use of an aqueous solution of hydrogen peroxide, acetic acid and peracetic acid (23/17/15) as a processing aid for the bacterial disinfection of the washing water used for cut carrots and lettuces, peeled garlic, sweet potatoes, persimmons, mangoes and avocados in processing

Determination of Dissociation Constants of (5,6-Dioxo-3-sulfoquinoline-7-yloxy)acetic Acid in Aqueous Solution at 25°C by Potentiometric Titration

The thermodynamic dissociation constants of (5,6-dioxo-3-sulfoquinoline-7-yloxy)acetic acid in aqueous solution at 25.0 ± 0.1°C were firstly determined using an improved potentiometric titration method. Based on the data of the potentiometric titrations and the least-square method, the values of pKa of this acid were calculated and the pKa1 = 1.795 ± 0.005 was assigned to quinoline ring and the pKa2 = 3.368 ± 0.010 for carboxyl group. The obtained results were analyzed in detail and compared with some similar known structures in order to conclude the accuracy and reliability of the improved potentiometric titration method.

Compressive strength enhancement of artificial bone using hydroxyapatite/fish-collagen nanocomposite

Marine collagen was used to prepare an artificial bone composite based on calcium phosphate nanocrystallites such as hydroxyapatite (HAp). The mechanical strength of calcium phosphate bone blocks is much lower than that of real bones. Hence, their strength needs to be enhanced for application of a human body. As-received freeze-dried fish collagen (fish COL) was dissolved in an acetic acid aqueous solution and then mixed with an aqueous H3PO4 solution. HAp crystallites were precipitated in the matrix of the fish-COL solution. The precipitated HAp/COL nanocomposite slurries were vacuum-filtered using a glass filter to prepare specimens for measuring compressive strength. Obtaining uniform density in the HAp/COL sample block was a challenge in this study. With a change in the COL content in the precipitated HAp/COL nanocomposite, the compressive strength was estimated using a universal testing machine.

Hydroxyapatite mineralization on chitosan-tragacanth gum/silica@silver nanocomposites and their antibacterial activity evaluation

The goal of this research was the fabrication of chitosan (CT)-tragacanth gum (TG)/SiO2 nanocomposite as a potential use in tissue engineering. For the antibacterial activity induction and stabilization of SiO2 nanoparticles (NPs) in the polymer matrix, SiO2 and green synthesized Ag NPs were hybrid with SiO2/Ag. Then, the obtained hybrids were inserted into the CT-TG blend, separately. The ultrasonic waves were applied, and the films were subsequently constructed by the solution casting technique. Finally, the CT-TG/SiO2 nanocomposites and CT-TG/SiO2@Ag nanocomposite films were studied by the variant techniques. The in-vitro bioactivity examination all samples was performed in a simulated body fluid. It was observed that hydroxyapatite was grown more on the surface of the CT-TG/SiO2@Ag (1/1) nanocomposite film in comparison to the other specimens, due to its high surface area and the presence of many specific functional groups. Furthermore, the antibacterial activity assessment of the all samples were performed against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria via well diffusion method. The higher inhibition zone diameters for the CT-TG/SiO2@Ag (1/1) nanocomposite film against both bacteria were observed in the presence of aqueous solution of acetic acid 1% v/v (11 and 13 mm) and deionized water (18 and 20 mm), respectively.

Dynamic Covalent Synthesis of Crystalline Porous Graphitic Frameworks

Summary Porous graphitic framework (PGF) is a two-dimensional (2D) material that has emerging energy applications. An archetype contains stacked 2D layers, the structure of which features a fully annulated aromatic skeleton with embedded heteroatoms and periodic pores. Due to the lack of a rational approach in establishing in-plane order under mild synthetic conditions, the structural integrity of PGF has remained elusive and ultimately limited its material performance. Here, we report the discovery of the unusual dynamic character of the C=N bonds in the aromatic pyrazine ring system under basic aqueous conditions, which enables the successful synthesis of a crystalline porous nitrogenous graphitic framework with remarkable in-plane order, as evidenced by powder X-ray diffraction studies and direct visualization using high-resolution transmission electron microscopy. The crystalline framework displays superior performance as a cathode material for lithium-ion batteries, outperforming the amorphous counterparts in terms of capacity and cycle stability.