Extraction of ethyl and methyl esters of polyunsaturated fatty acids with aqueous silver nitrate solutions
ABSTRACT Experiments on the extraction of ethyl and methyl esters of polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from various organic solvents into aqueous silver nitrate solutions were performed. The esters of PUFAs with high degree of unsaturation such as DHA and EPA could be selectively extracted into aqueous solutions. On the basis of the slope analysis, the extracted complex of PUFA ester (PUFA-E) was deduced to be (PUFA-E.nAg)n+ where n is the number of the carbon-carbon double bonds in PUFA. The distribution ratio D increased drastically with a decrease in temperature and also by addition of water-soluble alcohols such as methanol, ethanol, and n-propanol to aqueous solutions. The value of D was found to be highly dependent on the organic solvent used as the diluent of PUFA-E, and the D value of EPA ethyl ester (EPA-Et) was correlated by the activity coefficient of EPA-Et in the organic phase estimated by the UNIFAC equation.
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- "This case is identical to that of the observed higher distribution ratio (i.e. ratio of concentrations in the aqueous and organic phases) of C18 : 4n3 compared to C20 : 4n3 when the compounds were agitated in a biphasic mixture of a silver nitrate containing aqueous phase and n-hexane . A higher distribution ratio is indicative of a greater affinity of a compound toward the polar silver ion solid support. "
ABSTRACT: This article has been retracted at the request of the Editor. Please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).Reason: It duplicates significant parts of a paper that has already been published by the same authors in Enzyme Microb. Technol., volume 26 (2000) 516–529, doi:10.1016/S0141-0229(99)00191-X. One of the conditions of submission of a paper for publication is that authors declare explicitly that the paper is not under consideration for publication elsewhere. The scientific community takes a very strong view on this matter and we apologize to readers of the journal that this was not detected during the submission process.Enzyme and Microbial Technology 04/2000; 35(9-35):951-969. DOI:10.1016/S0032-9592(00)00126-6 · 2.97 Impact Factor
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ABSTRACT: Experiments on the separation of ethyl ester of eicosapentaenoic acid (EPA-Et) and that of docosahexaenoic acid (DHA-Et) contained in ethyl ester of bonito oil (bonito oil-Et) were performed using circulating liquid membranes (CIRLMs) containing sliver nitrate as a carrier. In this liquid membrane system an aqueous silver nitrate solution was circulated between a stirred vessel containing an organic solution of bonito oil-Et and another stirred vessel containing a receiving organic solvent. Using the CIRLM, two types of uphill facilitated transport of EPA-Et and DHA-Et in bonito oil-Et were demonstrated. The first type utilizes the distribution ratio of EPA-Et and DHA-Et, defined as the ratio of the concentration in the aqueous phase to that in the organic phase at equilibrium, which is remarkably dependent on the temperature, and the second uphill transport was based on the fact that the distribution ratio is considerably dependent on the solvent of the organic phase. A model of permeation through the circulating liquid membrane was proposed to explain the experimental results.Separation Science and Technology 08/1996; 31(14-14):1953-1969. DOI:10.1080/01496399608001022 · 1.20 Impact Factor
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ABSTRACT: Using silver ion as a carrier in oil/water/oil-type emulsion liquid membranes, batchwise extraction experiments were done to separate eicosapentaenoic acid ethyl ester (EPA-Et) from a model mixture consisting of EPA-Et and ethyl laurate. Moderate operating conditions were chosen for the concentration of Ag(I), the type of surfactant, and agitation strength. The emulsion liquid membranes thus formed were stable, and the concentration of Ag(I) and the surfactant types had strong effects on the permeation behavior of EPA-Et. The overall volumetric coefficients of EPA-Et obtained in the present study were equal to or smaller than those of organic solutes obtained with the data available in literature. It was found that the overall volumetric coefficients of these organic solutes increase linearly on a log-log scale, with increasing distribution ratios.Journal of Membrane Science 12/1997; 136:127-139. DOI:10.1016/S0376-7388(97)00162-2 · 4.91 Impact Factor