Separation of polyunsaturated fatty acids by selective inclusion in guanidinium‐1,5‐naphthalenedisulfonate‐2‐methoxyethanol host networks

Abstract

Hydrogen-bonded networks composed of guanidinium (G) and 1,5-naphthalenedisulfonate (NDS) have been developed for the selective inclusion and separation of fatty acid esters based on their degree of unsaturation. Porous crystalline networks have been synthesized and include fatty acid esters during crystallization from both methanol and 2-methoxyethanol. Crystalline networks formed in methanol are selective for the inclusion of saturates in preference to polyunsaturated fatty acid methyl esters, but their applicability is limited by the competing inclusion of the solvent methanol. In 2-methoxyethanol, a three-component host structure is formed that provides 4.1 x 4.7 A2 pores which are also selective for saturated fatty acid ester inclusion. These networks do not suffer from the competing inclusion of the solvent 2-methoxyethanol as is the case with methanol, and thus complete removal of initial saturated fatty acid 2-methoxyethyl esters is possible. Binary selectivity experiments on mixtures of the 2-methoxyethyl esters of saturated stearic acid and the omega-3 fatty acid alpha-linolenic acid reveal that this three-component network structure provides nearly complete resolution of these two guests in the crystal and filtrate fractions. Separation of the 2-methoxyethyl esters of alpha-linolenic acid from the monounsaturated oleic acid is also possible, although with decreased efficiency in comparison to removal of the saturated fatty acid ester.

Toward Understanding the Origin of Structural Phase Transition in Guanidinium Pyridinium 1,5-Naphthalenedisulfonate

“…Ward and co-workers performed a systematic investigation of the family of guanidinium organo(di)sulfonate compounds. − The attracting features of these compounds include (i) two-dimensional H-bonding networks, (ii) adjustable porosity, and (iii) ordered arrays of guest molecules. Modifications of the G and S components significantly alter the crystal packings of the corresponding guanidinium organo(di)sulfonate compounds. − …”

Enrichment process for α‐linolenic acid from silkworm pupae oil

“…The urea inclusion method effectively obtained a yield of 31.87% PUFAs from the desilked silkworm pupae oil but could not achieve a higher purity of ALA . Similar research results show that a single inclusion method usually could not produce high purity ALA from the oil extracted from natural resources . Although using powdered β‐CD results in enrichment of PUFAs, which may not be adequate for separating ALA from food systems and for β‐CD reuse .…”

“…The enrichment of n‐3 LCPUFAs has frequently been reported, including the purification of PUFAs by selective inclusion in guanidinium‐1,5‐naphthalenedisulphonate‐2‐methoxyethanol host networks , the enrichment of γ‐linolenic acid from plant oil by low temperature crystallization and improved fractional crystallization , the preparation of LCPUFAs by enzymatic acidolysis , the fractionation of polyunsaturated and hydroxy fatty acids by urea inclusion , and the purification of PUFAs by preparative column chromatography . These enrichment methods used to obtain PUFA‐rich fractions from natural oils are mostly associated with the number of double bonds and the degree of unsaturation in the carbon chain .…”

Selective Inclusion of Equatorial Isomers of Cyclohexane‐Polyols in Phosphonium Salt Hosts

“…[14] Few of these selective inclusion events have been translated into separation processes that make possible the recovery of pure guest molecules on a reasonable scale, although Toda and coworkers have reported some simple-to-apply bulk distillation processes, [15] and host networks (with and without solvent incorporated) that incorporate saturated fatty acids preferentially over those containing unsaturation have been employed in the enrichment of supernatant liquors in the desirable unsaturated fatty acids (as esters). [16] Separation of cis and trans isomers of cyclohexane-polyols has been achieved by means such as metal complexation, [17] distillation of boronic acid derivatives [18] or trapping, again through boronate formation, on a resin. [19] Differential binding of cis-cyclohexane-1,3-diol and transcyclohexane-1,4-diol by hosts containing both hydrogenbond-acceptor and -donor sites has also been reported.…”