The transfer mechanisms and analytical properties of the variable-valency drug cinchonidine across the liquid/liquid interface

The electrochemical transfer of cinchonidine across the liquid/liquid (L/L) interface was investigated by linear current-scanning polarography at the ascending water electrode and chronopotentiometry at the stationary water electrode. The relation between half-wave potential and the pH value of the aqueous phase was established and is in good agreement with the experimental results. Defending on the pH value in the aqueous phase, both singly- and doubly-charged cinchonidine cations can transfer across the L/L interface. This process is controlled simultaneously by diffusion and the rate of re-establishment of the disturbed protonation equilibrium. The effects of the supporting electrolyte, buffer and organic solvent on the polarographic wave were examined, and the transfer characteristics of cinchonidine in the aqueous and organic phases were compared. Direct determinations of cinchonidine in the aqueous phase and organic phase were carried out by linear current-scanning polarography with high selectivity. The linear range for determination is 5 × 10⁻⁵−1 × 10⁻³ mol dm⁻³.     

Modeling of Single Droplet Mass Transfer of Acetic Acid with Triisooctylamine-Based Solvent

The design of mass transfer equipment based on single droplet mass transfer data is still a great challenge, although having been subject of intensive discussion for decades already. Extraction with chemical reaction may rather contribute to additional problems when modeling single droplet mass transfer. Single droplet mass transfer of acetic acid from aqueous carrier into triisooctylamine based solvents modified with the Lewis acid modifier isodecanol and the diluent Shellsol T has been investigated. Mass transfer of acetic acid into triisooctylamine-based solvent droplets is strictly controlled (actually limited) by diffusion of the laden solvent from the interface into the droplet bulk phase.     

Extraction of Benzene and Naphthalene Carboxylic Acids Using Quaternary Ammonium Salts As a Model Study for the Separation of Coal Oxidation Products

Abstract

The ion‐pair solvent extraction of benzene‐ and naphthalene‐carboxylic acids has been investigated as a model study for the separation of coal oxidation products, which are formed by treatment with alkaline solutions at high temperatures. It was possible that benzene‐ and naphthalene‐dicarboxylic acids are extracted into several types of organic solvents with quaternary ammonium ions. The extraction equilibrium constants (K_ex) for benzoic acid, 1,2‐benzenedicarboxylic acid, 1,3‐benzenedicarboxylic acid, 1‐naphthoic acid, 2‐naphthoic acid, 2,3‐naphthalenedicarboxylic acid, and 2,6‐naphthalenedicarboxylic acid into chloroform were determined at 20°C. The difference of K_ex among the aromatic acids was sufficiently large for designing a separation method for these aromatic acids. It was unexpected that the extraction of dicarboxylic acids was slower than that of monocarboxylic acids, although the ion‐pair formation of aromatic carboxylate ion with quaternary ammonium ion is normally considered as a diffusion control reaction in aqueous phase. Thus, this fact suggests that the phase transfer of the ion‐pair from aqueous to organic phase is the rate‐determining step. Liner‐free‐energy relationship was observed for the monocarboxylic acids using different quaternary ammonium salts while that was ambiguous for the dicarboxylic acids. This is due to the steric influence of the counter ions for the magnitude of K_ex.     

Hydrolysis of Fish Oil by Lipases Immobilized Inside Porous Supports

A new assay was designed to measure the release of omega-3 acids [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] from the hydrolysis of sardine oil by lipases immobilized inside porous supports. A biphasic system was used containing the fish oil dissolved in the organic phase and the immobilized lipase suspended in the aqueous phase. The assay was optimized by using a very active derivative of Rhizomucor miehei lipase (RML) adsorbed onto octyl-Sepharose. Standard reaction conditions were: (a) an organic phase composed by 30/70 (v:v) of oil in cyclohexane, (b) an aqueous phase containing 50 mM methyl-cyclodextrin in 10 mM Tris buffer at pH 7.0. The whole reaction system was incubated at 25 °C. Under these conditions, up to 2% of the oil is partitioned into the aqueous phase and most of the 95% of released acids were partitioned into the organic phase. The organic phase was analyzed by RP-HPLC (UV detection at 215 nm) and even very low concentrations (e.g., 0.05 mM) of released omega-3 fatty acid could be detected with a precision higher than 99%. Three different lipases adsorbed on octyl-Sepharose were compared: Candida antarctica lipase-fraction B (CALB), Thermomyces lanuginosa lipase (TLL) and RML. The three enzyme derivatives were very active. However, most active and selective towards polyunsaturated fatty acids (PUFA) versus oleic plus palmitic acids (a fourfold factor) was CALB. On the other hand, the most selective derivatives towards EPA versus DHA (a 4.5-fold factor) were TLL and RML derivatives.     

Recovery of carboxylic acids C1?C3 with organophosphine oxide solvating extractants

This study was aimed at examining the use of the organophosphine oxides Cyanex^®921 and Cyanex^®923 for the extraction of formic, acetic and propionic acids from aqueous solutions. The stripping of monocarboxylic acids with water from the loaded extractants was also examined. The studies were aimed at determining the equilibrium conditions for extraction and stripping. Overall, the effect of the kind of extractant was not significant although Cyanex^®921 extracted carboxylic acids slightly better than Cyanex^®923 with 1:1 complexes being formed by both extractants with the acids during extraction. The efficiency of extraction depended on temperature, acid concentration and solvent, with toluene a better diluent for the extractants than octane or Exxsol^®D 220/230. Extraction efficiency increased as the concentration of acid in the feed decreased and, also, as the temperature increased, the amount of acid extracted decreased. The extraction and stripping isotherms were determined. The apparent enthalpy and entropy of the extraction reaction were determined. Distribution data for the transfer of carboxylic acids from aqueous (NaCl) solutions to organic solvents in the presence of trialkylphosphine oxide were determined at 293 K with the distribution ratios increasing as the concentration of NaCl increased. Copyright © 2005 Society of Chemical Industry     

Lipase-catalyzed synthesis of fatty acid amide (erucamide) using fatty acid and urea

Ammonolysis of fatty acids to the corresponding fatty acid amides is efficiently catalysed by Candida antartica lipase (Novozym 435). In the present paper lipase-catalysed synthesis of erucamide by ammonolysis of erucic acid and urea in organic solvent medium was studied and optimal conditions for fatty amides synthesis were established. In this process erucic acid gave 88.74 % pure erucamide after 48 hour and 250 rpm at 60 degrees C with 1:4 molar ratio of erucic acid and urea, the organic solvent media is 50 ml tert-butyl alcohol (2-methyl-2-propanol). This process for synthesis is economical as we used urea in place of ammonia or other amidation reactant at atmospheric pressure. The amount of catalyst used is 3 %.     

Analysis of volatile fatty acids in biological specimens by capillary column gas chromatography

A method was developed to analyze and quantify volatile fatty acids (VFA) such as acetic, propionic, butyric, isobutyric, valeric and isovaleric acids in biological specimens. To obtain good sample transfer into the chromatographic system an organic solvent had to be used together with an aqueous milieu, thus improving wetting properties of the liquid sample plug introduced into the column. Sample preparation was carried out under alkaline conditions in order to exclude or minimize sample losses due to sample transfer during the extraction and work-up procedure. A cold on-column injection was applied to avoid irregular discrimination of the various acids due to sample splitting and an automatic injection technique was used to accommodate the large number of samples generated from biological origin. Connection of a pre-column of wide internal diameter (0.53 mm) to the analytical column (0.32 m) was optimized and adapted to the nature of the injection solvent mixture consisting of acetonitrile, water and hydrochloric acid. To obtain well-separated and correctly quantifiable gas chromatographic peaks, it was essential to perform the chromatography under acidic aqueous conditions. Standard resolution conditions and response factors were evaluated. The chromatographic results of applying this method to biological specimens from both rats and humans are provided.     

Carl Hanson Medal

ABSTRACT

Nondispersive equilibrium separation of citric acid from an aqueous solution by reversible chemical complexatlon with trioctyl amine in a diluent of methyl isobutyl ketone is achieved in a microporous hydrophobic hollow fiber extractor. The extractor had a shell-and-tube configuration : a total of 102 hydrophobic polypropylene (Celgard X-20, 240 μm id, 290 μm od, Hoechst Celanese) hollow fibers potted in epoxy in a stainless steel tube of 0.46 cm id. The effective fiber length vas 18.5 cm and surface area/volume was 46.8 cm. Theoretical models have been developed to predict the rate of extraction of citric acid in such systems. It essentially considers diffusion of solute molecules through the boundary layers of the two phases, in addition to the diffusion through the organic liquid occupying the membrane pores, and reversible chemical equilibrium at the phase interface. Conventionally in an aqueous-organic system having a high distribution coefficient for small solutes with a hydrophobic fiber and organic in pores, the aqueous boundary layer resistance controls. Here that is true also except when the membrane resistance of the large citric acid-amine complex diffusing through the organic-filled pores is higher than the aqueous phase boundary layer resistance. Experimental observations show further that the back extraction rate of citric acid present in the solvent (amine-organic diluent) into aqueous sodium hydroxide is much lover than the extraction rate for such a system in the sane hollow fiber extractor.     

Linoleic acid absorption in the unaesthetized rat: Mechanism of transport and influence of luminal factors on absorption

Linoleic acid intestinal absorption was studied in the unanesthetized rat. At low (21–1260 μM) intraluminal concentrations, absorption took place by facilitated diffusion; while at high (1.26–2.5 mM) concentrations, simple diffusion was the predominant mechanism of transport. At low concentrations (840 μM), the equimolar additions of oleic, linolenic, and arachidonic acids or lecithin inhibited the absorption of linoleic acid. Substitution of potassium for sodium in the buffer solution, substitution of Tween 80 for sodium taurocholate, or decrease in the hydrogen ion concentration all resulted in decreased rate of linoleic acid's absorption. These experiments demonstrate that linoleic acid is absorbed by a concentration-dependent dual mechanism of transport. The absorption rate is modified by the pH, surfactant type and concentration, the simultaneous presence of other polyunsaturated fatty acids, and the thickness of the unstirred water layer.     

Separation of Polyunsaturated Fatty Acids with Silver Nitrate Using a Hollow-Fiber Membrane Extractor

Abstract

Solvent extraction of ethyl esters of polyunsaturated fatty acid such as eicosa-pentaenoic acid (EPA) and docosahexaenoic acid (DHA) was performed with an aqueous silver nitrate solution using a microporous hydrophobic hollow-fiber membrane extractor. The mixture of four kinds ethyl esters of fatty acids involved in fish oil was employed as a model solution of fish oil. Also studied was the extraction equilibria of these fatty acids at various conditions. It was demonstrated from the experimental results that EPA and DHA ethyl esters could be satisfactorily separated from ethyl esters of lower fatty acids such as oleic and palmitic acids. In addition, the effects of silver and ester concentrations in aqueous and organic feed solutions on the apparent permeabilities of fatty acids ethyl esters were investigated in extraction and stripping stages, respectively. It was concluded that the permeation rate was controlled by the diffusion across the membrane and the laminar boundary layer in the inner and outer sides of the hollow fiber.     

Back to the future: Fatty acids,the green genie to design smart soft materials

Fatty acids are widely used in industries for various applications as soaps or in their crystalline form. Fatty acid soaps are used as surface-active agent to stabilize foams and emulsions, for detergency, and surface wetting. Fatty acid molecules in organic solvents are used as low-molecular-mass organic gelators. Currently, there is a renewed interest in using fatty acids in industrial applications instead of petrochemical surfactants since fatty acid soaps are green surfactants. Fatty acids exhibit also many advantages, including the design of responsive soft-materials. Fatty acid soaps are natural pH and thermoresponsive surfactants, which can lead to responsive foams and emulsions. In their crystalline form, fatty acid crystals in both aqueous and non-aqueous solvents stabilize liquid foams. These crystals are also efficient in the production of liquid marbles. Fatty acids are solvosurfactants with the ability to form microemulsions and capillary suspensions. In this review, we illustrate how fatty acid molecules can be used in the manufacture of multiresponsive soft-materials ranging from aqueous and non-aqueous foams, emulsions, nanoemulsions, microemulsions, liquid marbles and capillary suspensions.     

Engineering Cytochrome P450 BM3 for Terminal Alkane Hydroxylation

Enzymes that catalyze the terminal hydroxylation of alkanes could be used to produce more valuable chemicals from hydrocarbons. Cytochrome P450 BM3 from Bacillus megaterium hydroxylates medium‐chain fatty acids at subterminal positions at high rates. To engineer BM3 for terminal alkane hydroxylation, we performed saturation mutagenesis at selected active‐site residues of a BM3 variant that hydroxylates alkanes. Recombination of beneficial mutations generated a library of BM3 mutants that hydroxylate linear alkanes with a wide range of regioselectivities. Mutant 77‐9H exhibits 52% selectivity for the terminal position of octane. This regioselectivity is octane‐specific and does not transfer to other substrates, including shorter and longer hydrocarbons or fatty acids. These results show that BM3 can be readily molded for regioselective oxidation.     

微乳液体系中酶促反应的研究

综述了在微乳液体系中的酶促反应。讨论了表面活性剂、溶剂和助表面活性剂的选择对微乳液中酶促反应的影响及酶在反胶束中的增溶位置。庚烷、辛烷、壬烷是较好的溶剂 ,酶分子可增溶于反胶束中的水池 ,或吸附于油—水界面层极性头微乳液膜附近。描述了微乳液中水含量和缓冲溶液 pH对酶活力的影响 ,酶活力与水含量一般呈钟形曲线 ,与 pH可呈钟形或S形曲线。     

Interfacial Mass Transfer in the Reactive Extraction Process of Succinic Acid from Viscous Aqueous Solutions

The reactive extraction of succinic acid with TOA dissolved in butyl acetate from viscous aqueous solutions which simulate the rheological behavior of Actinobacillus succinogenes broths underlined the strong influence of viscosity and pH on interfacial mass flow, mass transfer driving force, and mass transfer coefficient. The magnitudes of these effects are attenuated by 1-octanol addition into the solvent phase, the interfacial mass transfer rate being accelerated for 1.2-3 times, depending on the apparent viscosity and the pH-value of the aqueous solution. The influences of the extraction parameters and mechanism have been included in a mathematical model adequate for the solute mass transfer coefficient from aqueous to organic phase.     

REACTIVE EXTRACTION OF LEVULINIC ACID FROM AQUEOUS SOLUTIONS WITH TRI-n-OCTYLAMINE (TOA) IN 1-OCTANOL: EQUILIBRIA,KINETICS, AND MODEL DEVELOPMENT

Levulinic acid, a carboxylic acid containing a ketone structure, can be used as an acidulant in foods and beverages. Reactive extraction is a promising alternative for the recovery of carboxylic acids from aqueous streams. The design of an amine extraction process requires kinetic data for the acid-amine + solvent system used. In this study, equilibrium and kinetic data on the extraction of levulinic acid from aqueous solutions using tri-n-octylamine (TOA) in 1-octanol have been determined. The mass transfer coefficients of levulinic acid, TOA, and 2:1 levulinic acid-amine complex in 1-octanol were calculated from the acetic acid mass transfer coefficient, which was determined by measuring its fluxes of simple diffusion from kerosene to water. Based on the Hatta number and the criterion given by Doraiswamy and Sharma, the reaction regime has been found to be instantaneous reaction regime occurring at the interface on the organic phase side. An extraction model comprising equilibrium complexation constant w.r.t 2:1 levulinic acid-TOA complex formation, K_E2i (14.794 (m³ kmol^?1)²), and complex mass transfer coefficient, k_B2A (2.193 × 10^?6 m s^?1), has been developed.     

Removal of Traces of Pentachlorophenol from Aqueous Acidic Solutions by Solvent Extraction and Solvent Sublation

Abstract

The removal of pentachlorophenol (a hydrophobic compound of low vapor pressure) from aqueous acidic solutions was studied using solvent sublation (a surface chemical technique) and solvent extraction. Both methods gave appreciable removals in highly acidic solutions (pH = 2.5), but solvent sublation had the added advantage of minimal phase contact of the organic solvent with water and increased removals under certain circumstances. Solvent sublation was also found to be more effective than conventional fine bubble aeration. The removal of pentachlorophenol (PCP) was considerably smaller at pH's near the pK_a of PCP. PCP removal by solvent sublation was enhanced by increasing ionic strength and also by the presence of small amounts of an ionic surfactant in the aqueous phase. The technique of solvent sublation was tried on an actual wastewater sample from a wood preserving industry. pH adjustment, removal of suspended solids, addition of sodium chloride, and subsequent solvent sublation into mineral oil reduced the PCP concentration in the aqueous waste by 99.7%.     

Copper Ion Extraction by a Mixture of Fatty Hydroxamic Acids Synthesized from Commercial Palm Olein

Abstract

A mixture of fatty hydroxamic acids (FHA), synthesized from a commercial palm olein, was evaluated as an extractant for extraction of copper ion from aqueous media. The content of hydroxamic acid groups in the FHA, analyzed by elemental analysis, was 3.52 mmol/g. Copper extraction from aqueous media was studied by solvent extraction technique using octanol as an organic phase. The extraction of copper ion was through the formation of 1∶2 (Cu(II)∶FHA) complex, pH dependent and not affected by the presence of a large amount of Co(II), Ni(II), Cd(II) and Zn(II) ions.     

Surface active N-acylglutamate: I. Preparation of long chain N-acylglutamic acid

Long chain N-acylglutamic acid was prepared in a high yield by a reaction of glutamic acid with fatty acid chloride in a mixed solvent of water and a water miscible organic solvent such as acetone, methyl ethyl ketone, dioxane, tetrahydrofuran,t-butyl alcohol or cyclohexanone. In this reaction the composition of the mixed solvent influenced the yield of N-acylated glutamic acid and the best yield was obtained when the reaction was carried out in the mixed solvent comprising 30–60% v/v of the organic solvent. Long chain N-acylaspartic acid was also obtained in a high yield by the same method. As the other method to obtain N-lauroyl-D L-glutamic acid, it was examined that N-acyl-α-aminoglutarodinitrile which was obtained by a reaction of α-aminoglutarodinitrile with fatty acid chloride was hydrolyzed with an aqueous alkaline solution. The salts of long chain N-acylglutamic acid are known as the surface active agents that react mildly on the human skin.     

Determination of fatty acid composition via chemical ionization-mass spectrometry

The analysis of fatty acid methyl esters by chemical ionization-mass spectrometry via a new interface system is described. The sample is applied to the interface system in dichloromethane containing trideuteromethyl (CD₃) fatty acid esters as internal standards and dodecanol as a carrier. The esters are evaporated into a carrier gas of nitrogen in the interface and then drawn through a transfer system where residual traces of solvent are removed and the esters are concentrated by a porous silver membrane separator. The sample, now enriched in the carrier gas, is passed into the mass spectrometer where it is analyzed by selective multiple ion monitoring using isobutane as the reagent gas. The method, which takes less than a minute, is computerized for the quantitative analysis of the 19 most common fatty acids occurring in major portions in animal and plant tissues. The accuracy and precision of the method was demonstrated and compared to fatty acid analysis by gas liquid chromatography on several fats.     

The hydrophilization process for the separation of fatty materials

Fats and derivatives of fats consist of mixtures of components differing in chain length and saturation. Apart from the fractional distillation, several methods exist for the separation which are based on the different melting-point and solubility behavior of these components. Modern separation processes use recrystallization from organic solvents, press or filtration methods. The hydrophil process uses an entirely different approach. A mixture of solid and liquid fatty material, for instance, tallow fatty acid, is treated with an aqueous solution of surfaceactive substances. The liquid fatty acids are removed from the surface of the fatty acid crystals and emulsified in the aqueous phase. The crystals are hydrophilized so that they leave the oil phase and completely enter the aqueous phase, where they are suspended. In a solid-bowl centrifuge the aqueous solution, containing the suspended crystals of stearic acid, is separated from the oleic acid phase. The stearic acid is recovered by heating the aqueous suspension above the melting point. The composition and concentration of the sufactants, the salt content and the volume of the aqueous phase, the crystallization performance of the fatty material, and the apparatus design are important in the efficiency of the separation. The composition of the components is besed on the phase diagram which controls iodine number, melting or cloud point of the oleic and stearic acid in relation to the separation temperature. The stearic and oleic acid is practically identical with the expeeted composition from the phase-diagram readings. This separation principle can be used for fatty acids, fatty alcohols, or fats. Presented at the AOCS Meeting, New Orleans, May, 1967.