Extraction of ethyl and methyl esters of polyunsaturated fatty acids with aqueous silver nitrate solutions

Industrial & Engineering Chemistry Research (Impact Factor: 2.24). 04/2002; 33(2). DOI: 10.1021/ie00026a026
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    ABSTRACT: The effect of solvents on the facilitated transport of ethyl ester of docosahexaenoic acid (DHA-Et) was studied in the system where feed phase, membrane phase and receiving phase had the same solvent. The carrier of DHA-Et was Ag+ and Nafion® membrane was used as the support. First, the swelling behavior of Nafion® membrane was investigated in various solvents. The solvent contents in the membrane were well correlated with the donor number (DN) of the solvents and had the maximum at DN of about 25kcal/mol. Stability constants of complexes between Ag+ and DHA-Et were obtained from the extraction equilibrium experiments. The stability constants increased with the decrease of DN of the solvents. From the balance of two effects on the membrane swelling and the stability constants, the solvent with DN∼19kcal/mol, that is aqueous methanol solvent showed the highest permeance of DHA-Et in Ag salt form membrane. When DMF, DMA and TBP, which have about 25kcal/mol of DN, were used as the solvent, the permeance in Na salt from membrane was high due to the high membrane swelling, while the facilitation factors and the selectivities of DHA-Et to ethyl ester of oleic acid were low because the complexation ability between Ag+ and DHA-Et was poor. The heat-treatment of Nafion® membrane in glycerin and the increase of the experimental temperature were found to be useful to enhance the permeances because of the larger membrane swelling.
    Journal of Membrane Science 07/1999; 159(1):1-10. · 4.90 Impact Factor
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    ABSTRACT: Arachidonoyl ethanolamide is an endogenous cannabinoid neurotransmitter that potentially has therapeutic properties. In this study, we report an enzymatic method to synthesize this bioactive ethanolamide. First, free fatty acids were obtained from arachidonic acid-rich oil and then arachidonic acid was enriched by urea inclusion and AgNO3 solution fractionation. Arachidonic acid content was increased from 40.2 to 78.4 % with 27.6 ± 1.8 % total fatty acid mass yield (w/w, relative to total free fatty acid) after urea inclusion. Purification of arachidonic acid by AgNO3 solution fractionation was optimized, and under the optimal conditions, a product with 90.7 % arachidonic acid was obtained with 80.4 % mass yield (w/w, relative to total free fatty acid). Finally, arachidonoyl ethanolamide was synthesized by reacting the purified arachidonic acid with ethanolamine in hexane using Novozym 435 lipase of Novozymes America (Blair, NE), which resulted in the formation of 88.4 ± 0.6 % arachidonoyl ethanolamide with 72.7 ± 2.2 % mass yield. The main novelties of this study are the enrichment of polyunsaturated fatty acids by AgNO3 solution fractionation which has received little attention in recent years, and this is the first time the synthesis of arachidonoyl ethanolamide is reported.
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    ABSTRACT: In this paper, we demonstrate that the hydrophobic ionic liquid (IL) such as 1-hexyl-3-methyl imidazolium hexafluorophosphate, [hmim][PF6], with silver salt, e.g. AgBF4, is an excellent extraction phase to separate and enrich omega-3 polyunsaturated fatty acid methyl esters (PUFAMEs) from the mixed solution containing closely related saturated, monounsaturated or diunsaturated fatty acid methyl esters. With this silver salt-ionic liquids extraction phase, the health-beneficial omega-3 PUFAMEs such as methyl ester of all-cis-5,8,11,14,17-eicosapentaenoic acid (20:5 or EPA) and methyl ester of all-cis-4,7,10,13,16,19-docosahexaenoic acid (22:6 or DHA) were largely enriched from 18% (wt %) in the original cod liver oil to greater than 80% in the 1-hexene stripping solvent. The unique properties of nonvolatility and adequate polarity allow ILs to dissolve or suspend silver salts and to be conveniently adopted as extraction phase in separating PUFAMEs. The ILs with different hydrophobicities and different silver salts were screened to obtain an optimal combination of IL and silver salt with the highest extraction capability and selectivity. The screening results showed that AgBF4 exhibited high extraction capability in the hydrophobic ILs but little or no extraction capability in the hydrophilic ILs. Furthermore, the high extraction capability of AgBF4 in hydrophobic ILs was much greater than that of AgBF4 in traditional silver-water or silver-alcohol extraction systems. Pretreating the silver-ILs extraction phase with steric hindered short chain olefins could significantly enhance its extraction selectivity for PUFAMEs. Nine runs of the IL-silver extraction phase showed no obvious decrease in its extraction capabilities and selectivities.
    Separation Science and Technology 01/2008; 43(8):2072-2089. · 1.16 Impact Factor