Fatty Acids In Aqueous Solution Research Articles

Self-Assembly of Palmitic Acid in the Presence of Choline Hydroxide.

To disperse fatty acids in aqueous solution, choline, a quaternary ammonium ion, has been used recently. So far, only the self-assembly of myristic acid (MA) in the presence of choline hydroxide as a function of the molar ratio has been investigated, and, thus, the current understanding of these fatty acid systems is still limited. We investigated the self-assembly of palmitic acid (PA) in the presence of choline hydroxide (ChOH) as a function of the molar ratio (R) between ChOH and PA. The self-assemblies were characterized by phase contrast microscopy, cryo-TEM, small-angle X-ray scattering, and 2H NMR. The ionization state of PA was determined by pH, conductivity, and FT-IR measurements. With increase in R, various self-assembled structures, including vesicles, lamellar phase, rigid membranes (large sheets, tubules, cones, and polyhedrals), and micelles, form in the PA/ChOH system, different from those of the MA/ChOH system. The change in R induces pH variation and, consequently, a change in the PA ionization state, which, in turn, regulates the molecular interactions, including hydrogen bonding and electrostatic interaction, leading to various self-assemblies. Temperature is an important factor used to tune the self-assembly transitions. The fatty acid choline systems studied here potentially may be applicable in medicine, chemical engineering, and biotechnology.

Sustainable harvesting of aqueous phase fatty acids by expanded graphite and isopropyl alcohol

Fatty acids (FA) from organic wastes are environmentally friendly raw materials with high economic value ranging from fuels to oleo-chemicals for growing diversity of products. In this study, expanded graphite (EG) and isopropyl alcohol have been used to adsorb and concentrate the low content of FA in aqueous solution to replace the existing solid-phase extraction methods. The results showed that the maximum adsorption capacity of EG was more than 8.2 g-FA/g due to the inter-latticed structure of graphene sheets, and subsequent coalescence of FA droplets. The extraction efficiency of isopropyl alcohol was always higher than those of dichloromethane and ethanol for the recovery of absorbed FA due to the lower surface tension and higher miscibility with water. After 5 times of recycle, although the specific FA adsorption was decreased 42% of raw EG, extraction efficiencies by isopropyl alcohol were not changed. In conclusion, our study suggested that the EG and isopropyl alcohol could achieve the efficient and environmentally friendly harvesting of low concentration of FA in aqueous solutions during the biological conversion of organic matters in food waste.

Sulfonated methyl esters of fatty acids in aqueous solutions: Interfacial and micellar properties

The interest to sulfonated methyl esters of fatty acids (SME) has been growing during the last decade, because these surfactants are considered as an environmentally friendly and renewable alternative of the linear alkyl-benzene sulfonates (LAS). Here, we present a quantitative study on the properties of aqueous SME solutions, and especially on their surface tension isotherms, critical micelle concentration (CMC) and its dependence on the concentration of added NaCl. It is demonstrated that the CMC of an ionic surfactant determined by electrical conductivity is insensitive to the presence of a small nonionic admixture, so that the CMC values determined by conductivity represent the CMC of the pure surfactant. Using SME as an example, we have demonstrated the application of a new and powerful method for determining the physicochemical parameters of the pure ionic surfactant by theoretical data analysis (“computer purification”) if the used surfactant sample contains nonionic admixtures, which are present as a rule. This method involves fits of the experimental data for surface tension and conductivity by a physicochemical model based on a system of mass-balance, chemical-equilibrium and electric-double-layer equations, which allows us to determine the adsorption and micellization parameters of C12-, C14-, C16- and C18-SME, as well the fraction of nonionic admixtures (if any). Having determined these parameters, we can further predict the interfacial and micellization properties of the surfactant solutions, such as surface tension, adsorption, degree of counterion binding, and surface electric potential at every surfactant, salt and co-surfactant concentrations.

Aggregation Behavior of Tetraenoic Fatty Acids in Aqueous Solution

Aggregation Behavior of Tetraenoic Fatty Acids in Aqueous Solution

Aggregation Behavior of Tetraenoic Fatty Acids in Aqueous Solution

Welche Packung wollen Sie? Charakteristische blauverschobene UV-Absorptionen wurden genutzt, um die Aggregation von C24-Tetraen-Fettsäuren in wässriger Lösung zu verfolgen. Die Aggregation verläuft über drei Zustände (K→T1→T2; siehe Bild), und es wird vorgeschlagen, dass alle diese Aggregate lokal lamellar sind, sich aber im Packungsmodus des Fettsäure-Rückgrats unterscheiden.

Fatty acid-binding proteins in the heart.

Long-chain fatty acids are important fuel molecules for the heart, their oxidation in mitochondria providing the bulk of energy required for cardiac functioning. The low solubility of fatty acids in aqueous solutions impairs their cellular transport. However, cardiac tissue contains several proteins capable of binding fatty acids non-covalently. These fatty acid-binding proteins (FABPs) are thought to facilitate both cellular uptake and intracellular transport of fatty acids. The majority of fatty acids taken up by the heart seems to pass the sarcolemma through a carrier-mediated translocation mechanism consisting of one or more membrane-associated FABPs. Intracellular transport of fatty acids towards sites of metabolic conversion is most likely accomplished by cytoplasmic FABPs. In this review, the roles of membrane-associated and cytoplasmic FABPs in cardiac fatty acid metabolism under (patho)physiological circumstances are discussed.

Binodal curve of two liquid phases and solid-liquid equilibrium for water + fatty acid + ethanol systems and water + fatty acid + acetone systems

To determine the liquid-liquid-solid three-phase equilibrium (LLSE), binodal data of the liquid-liquid equilibrium (LLE) and the solid-liquid equilibrium (SLE) have been measured for the ternary water + acetone or ethanol + lauric acid, myristic acid or palmitic acid systems. The binodal region for two liquid phases increases successively in the following order of the third component: lauric acid < myristic acid < palmitic acid. The binodal regions of the ternary systems with acetone as the second component are larger than those for ethanol. These binodal curves are not highly sensitive to temperature. The isothermal solubility of these fatty acids is considerably reduced when the water content in the aqueous phase increases. The solubility of fatty acids is successively reduced in the following order: lauric acid > myristic acid > palmitic acid. The solubility of fatty acids in aqueous solutions containing acetone is smaller than in those containing ethanol. Predictions of both the binodal curve for LLE and the SLE curve by the UNIFAC method and the NRTL equation do not represent the experimental data. However, data of the binodal curve and solubility are well correlated by the NRTL equation, and also the LLSE relationship could be represented.

5,6-Dimethoxy-2-(4′-Hydrazinocarbonylphenyl)benzothlazole as a Highly Sensitive and Stable Fluorescence Derivatization Reagent for Carboxylic Acids in High Performance Liquid Chromatography

Abstract 5,6-Dimethoxy-2-(4-hydrazinocarbonylphenyl)benzothiazole (BHBT-hydrazide) was found to be a highly sensitive and stable fluorescence derivatization reagent for carboxylic acids in liquid chromatography. Its reactivity was investigated for various C18:0-C22:6 saturated and unsaturated fatty acids. The reagent readily reacted with the fatty acids in aqueous solution in the presence of pyridine and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at 37°C to produce the corresponding fluorescent derivatives. The derivatives were separated on a reversed-phase column, TSK-gel ODS 120T, with gradient elution using 40–100% (v/v) aqueous acetonitrile, and were detected spectrofluorimetrically at 447 nm with excitation of 365 nm. Calibration curves were linear over the range 10 fmol–5.0 pmol per 20-μl injection (r=0.992−0.999). The relative standard deviations for ten replicated determinations did not exceed 2.0% for any of the fatty acids (1.0 nmol/ml). The detection limits (signal-to-noise ratio=3) for the acids were 1–2 fmol for an injection volumn of 20 μl. Further, the BHBT derivative of stearic acid was synthesized to examine the fluorescence properties.

Oxidative Stability of Geometric and Positional Isomers of Unsaturated Fatty Acids in Aqueous Solution

The geometric and positional isomers of monoenoic, dienoic and trienoic fatty acids were oxidized in aqueous solution using Fe2+-ascorbic acid as the catalyst. The oxidative stability of each acid was assessed based on decrease in unoxidized substrate content. The trans and cis isomers of dienoic and trienoic acids were found to differ in stability while this parameter for trans isomers of monoenoic acids was essentially the same as that of the cis isomers. The oxidative stability of monoenoic acid increased with the proximity of olefinic bonds to methyl ends and shortness of chain length. The effect of chain length on oxidative stability was the same for isomers of methylene-interrupted trienoic acids. In aqueous solution, oleic acid was more oxidatively stable than linoleic acid, but oxidized more rapidly than α-linolenic acid. This order for the oxidative stability of unsaturated C18 acids was different from that in air. The relative oxidative stability of nonmethylene-interrupted dienoic and trienoic acids in aqueous solution also differed from that in air.

6,7-Dimethoxy-1-methyl-2(1H)-quinoxalinone-3-propionylcarboxylic acid hydrazide: a highly sensitive fluorescence derivatisation reagent for carboxylic acids in high-performance liquid chromatography

6,7-Dimethoxy-1-methyl-2(1H)-quinoxalinone-3-propionylcarboxylic acid hydrazide was found to be a highly sensitive fluorescence derivatisation reagent for carboxylic acids in high-performance liquid chromatography. The reaction conditions were optimised for various C5–C20 saturated fatty acids. The reagent readily reacted with the fatty acids in aqueous solution in the presence of pyridine and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at room temperature to produce the corresponding fluorescent derivatives, which were separated on a reversed-phase column, Biofine RPC-SC 18 B, by gradient elution with 40–100% aqueous methanol. The derivatives were detected spectrofluorimetrically at 447 nm with excitation at 365 nm. The detection limits (signal to noise ratio = 3) for the acids were 3–6 fmol for an injection volume of 10 µl. The reagent was also applied to the derivatisation of some metabolites of arachidonic acid.

A Rapid, Precise Determination of C1-C4 Normal Volatile Fatty Acids in Aqueous Solutions by Gas Chromatography

The objective of this work is to develop a rapid and precise method for determining free volatile fatty acids (VFAs) in cellulosic polymers. The VFAs are extracted with water and determined quantitatively by gas chromatography (GC). A thermal conductivity detector (TCD) is used to detect formic acid, and separation of the VFAs is achieved by using a wide-bore fused-silica Carbowax 20M capillary column. The method is rapid and precise, and a coefficient of variation of 3% for formic acid is determined.

Insoluble mixed monolayers: III. The ionization characteristics of some fatty acids at the air/water interface

The surface pressure versus molecular area isotherms of stearic, oleic, and linoleic acids spread at aqueous solution/air interfaces have been recorded within a wide range of pH (1 to 10.7). The dissolution process of the surfactant from the monolayer into the alkaline subphases is investigated. Collapse pressure and equilibrium spreading pressure are determined. The relationship between them is discussed by presuming that the freshly collapsed bulk phase is in a metastable mesomorphous state. Molecular model studies show the limiting molecular area and the collapse one of the studied acids to be determined by the space necessities of the hydrocarbon chain in its most extended conformation. Apparent surface acidity constants ( K a) are derived from the dependence of the collapse pressure on pH. For stearic, oleic, and linoleic acidsp K a , values of 5.63, 6.22, and 5.94 were obtained, respectively. Correlation between the apparent surface acidity constants and the acidity constants of fatty acids in aqueous solutions is discussed.

Oxygen uptake during the gamma-irradiation of fatty acids.

The radiation-induced oxidation of saturated and unsaturated fatty acids in aqueous solutions has been estimated by measurement of the continuous uptake of oxygen using an oxygen electrode. Chain reactions, initiated by HO radicals, are easily identified to be occurring in the case of unsaturated fatty acids. Other mild oxidation agents, namely (SCN)-.2, Br-.2 and N.3, are also found to be capable of oxidizing the polyunsaturated fatty acids. Evidence is presented that O-.2 may also initiate peroxidation. The oxidation of the polyunsaturated fatty acids is dependent on dose rate, fatty acid concentration, temperature and the presence of antioxidant and other protective agents. Kinetic studies of the reaction of (SCN)-.2 and Br-.2 with linoleic and linolenic acids have been carried out using pulse radiolysis. The bimolecular rate constants for both radical species with the lipids are approx 10(7) mol-1 dm3 s-1, below their critical micelle concentrations, and decrease at higher concentrations due to micelle formation.

Direct gas chromatographic determination of short-chain (C 2–C 4) volatile fatty acids in aqueous solutions

1. 1. A gas chromatographic method for direct analysis of short-chain (C 2–C 4) volatile fatty acids (VFA) in aqueous solutions completely without ghosting problems is described. 2. 2. The sensitivity for routine quantification of VFA is less than 1 nmol. 3. 3. An example is given for analysis of volatile fatty acids (acetic and propionic) from anoxic incubation of the freshwater annelid Tubifex tubifex.

Separation of Sodium Salts of Fatty Acids in Aqueous Solutions by Reverse Osmosis Membranes

The removal of some sodium salts of fatty acids in aqueous solutions was studied by reverse osmosis process (batch system) using cellulose acetate membranes.The results were as follows : When the concentration of sodium salts of fatty acids is 100 mg/l, the rejection showed the low values when the carbon number of alkyl groups on the sodium salts of fatty acids was C2 to C8, and when the carbon number of alkyl groups increases to C10C18 the rejection tends to be higher. The difference in water permeability was little between C2 to C18 sodium salts of fatty acids.The rejection increased as the surface tension of sodium salts of fatty acids became lower.

Dimerization of Lower Fatty Acids in Aqueous Solutions

Dimerization of Lower Fatty Acids in Aqueous Solutions

Influence of the products of phospholipolysis of phosphatidylcholine on micellar solubilization of fatty acids in the presence of bile salts.

1. The solubility of fatty acids in aqueous solutions containing bile salts and lysolecithin at pH values between 2-0 and 7-4 was studied. Both the 1-acyl and 2-acyl isomers of lysolecithin increased the solubility of fatty acids to the same extent, the order of solubility being linoleic greater than oleic greater than elaidic greater than palmitic greater than stearic. 2. The influence of the products of phospholipolysis of lecithin on palmitic acid solubility was determined. On a molar basis, lysolecithin was more effective than were bile salts in promoting the solubilization of the fatty acid. 3. In bile salt solutions in which the phospholipid concentration was constant on a molar basis, in solubility of palmitic acid decreased linearly with the progressive replacement of lecithin by lysolecithin. Palmitic acid was solubilized to the same extent on replacing lecithin with lysolecithin on a constant weight basis. 4. In bile salt solution containing lysolecithin and oleic acid in equimolar amounts, the solubility of palmitic acid was similar to that in bile salt solution containing lecithin in equivalent proportion. 5. The results are discussed in relation to the action of phospholipolytic activity on the intestinal absorption of fatty acids in sheep.

The molecular depression of the surface tension by fatty acids in aqueous solution

When fatty acids are dissolved in water and the lowering of the surface tension is plotted against the natural logarithm of the concentration in grams per kilogram, the equation for the rectilinear midportion of the curve is F= aRT log eg + aRTM 14 , where a is the molar surface excess calculated from the slope, aRT, g is the gram concentration, and M is the molecular weight of the fatty acid calculated from the intercept, aRTM/14.

The determination of short-chain fatty acids in aqueous solution by gas-liquid chromatography

A method is presented for the direct determination of short-chain fatty acids in aqueous solution by gas-liquid chromatography. A flame ionization detector and glass columns packed with Chromosorb 101 (a polystyrene-divinylbenzene resin developed by Johns-Manville), coated with 3 per cent F.F.A.P., were used. Complete separation of both the normal and iso-acids (from C 2 to C 6) was achieved. The linearity of the detector over the concentration range 0 to 2500 mg 1 −1 for C 2 and C 3 and 0–1000 mg 1 −1 for the C 4 to C 6 acids was also established. Per unit weight, acetic acid gave responses of the order of those of the higher homologues. Column characteristics (as evidenced by retention times and detector responses) remained unimpaired after well over 500 injections of fatty acid solutions, water and digester samples.

Dehydration temperatures of polyethylene glycol esters of high molecular weight fatty acids in aqueous solutions

Dehydration temperatures of polyethylene glycol esters of high molecular weight fatty acids in aqueous solutions