Anion exchange and aggregation of dicyanocobalamin with quaternary ammonium salts in apolar environment

Abstract

Liquid-liquid extraction of dicyanocobalamin was performed, using quaternary ammonium salts (Aliquat 336) as liquid ion exchangers. A chemical model, taking into account aggregation of the cyanide and dicyanmbalamin ammonium salts in the organic phase, results in quantitative agreement with experimental data, covering the whole concentration range of practical interest. Vitamin B12 is the moat complex of all vitamin molecules. Although total chemical synthesis was achieved once in the laboratory, it is made industrially by biosynthesis. Vitamin B12 or cyanocobalamin (Cbl) is obtained as a dilute component in a fermentation broth. Its purification to obtain a pharmaceutical grade product can be achieved by a two-stage ion-exchange process using an ion-exchange resin with substituted ammonium salts (Shafer and Holland, 1955).As part of an investigation of other ways to concentrate and purify vitamin B12, (Calvarin, 1989), this article describes a liquid-liquid extraction experiment where Cbl is extracted as an anionic cyanide complex CblCN-by an organic phase containing quaternary ammonium sdta (Aliquat 336) used as anion exchangers. The results are represented by a simple, but credible, empirical ideal associated solution model assuming aggregation of species in both phases. The species involved in this extraction are presented in Figure 1. Experimental SectionMaterials. Vitamin B12 was obtained from RhonePoulenc as a pharmaceutical grade product of 96% purity. Sodium cyanide and p-xylene were purchased as Prolabo Rsctapur products, dodecane as a Prolabo technical grade product, and l-decanol as a Fluka Purum product.The mixture of trialkylmethylammonium chlorides (trialkyl= C8-Cl0, mainly capryl), known under the name of Aliquat 336, was bought as an organic solution from Fluka. It was converted to cyanide salts before extraction experiments, by repeated contacts with concentrated aqueous sodium cyanide solutions. In the conditions of the experiments, the quaternary ammonium cations form ion pairs only with CN-and CblCN-, denoted respectively as ACN and ACblCN, and various aggregates. It does not diesolve in the aqueous phase as was experimentally verified.Analytical Methods. Water Karl-Fischer titrations were performed on a Tacussel Aquaprocesseur. Interfacial tensions were measured on a Kruas K10 ring tensiometer. Cbl and CblCN-concentrations in the aqueous phase were measured on a Hewlett-Packard 8452 diode-array spectrophotometer, between 480 and 820 nm. They have absorption peaks at 551 nm for Cbl and 580 nm for CblCN-, -0888-58851 921 2631-1705$03.OO/ 0 and therefore both concentrations can be obtained simultaneously. Cyanide concentrations in aqueous phase were measured on a Metrohm 512 potentiometer by Ag+ titration: this method does not distinguish free cyanide anions and CblCN-complex, and the result is therefore an overall cyanide concentration. The total ammonium concentration in the organic phase is the sum of the ionpair [ACN] and [ACblCN] concentrations; it is measured by Ag+ potentiometric titrati...

Equilibrium and kinetic studies of the extraction of chelated copper(II) anions with Aliquat 336

“…20±22 In the extraction of dicyanocobalamin with Aliquat 336, a chemical equilibrium model with six ®tting parameters was proposed to account for the aggregation of species in the organic phase. 20 Although the deviation was reduced below 10%, the mathematical complexity makes it inconvenient for further application.…”

Effect of formaldehyde on Cu(II) removal from synthetic complexed solutions by solvent extraction

“…(12) and (13) are in mol/m 3 . The non-ideality of organic phase is likely due to the interaction or aggregation of the organic-phase species involving quaternary amines [20][21][22]. For example, it was found that most of tri-n-octylmethylammomium nitrate in benzene forms tetramers in the range of amine concentration of 10-1000 mol/m 3 [21], because of the possible formation of O H bonds within a given compound.…”

The reactive extraction of phenylalanine with aliquat 336: Buffer co-extraction equilibrium and mass transfer kinetics

“…It has be tested as a potential extractant for conventional reactive-extraction processes, as well as a carrier during emulsion liquid and supported liquid membrane processes. Studies have been performed on the extraction equilibrium of various carboxylic acids (Coelhoso et al, 1996(Coelhoso et al, , 1997Yang et al, 1991), amino acids and di-and tri-peptides (Behr and Lehn, 1973;Chan and Wang, 1993;Haensel et al, 1986;Handojo et al, 1992;Hano et al, 1991Hano et al, , 1993Lazarova, 1993;Reisinger and Marr, 1993;Scarpello, 1998;Thien et al, 1988;Uddin et al, 1990Uddin et al, , 1992, vitamin B 12 (Calvarin et al, 1992;Galan et al, 1994) and 6-Aminopenicillanic acid (Bora et al, 1997). These have all shown Aliquat 336 to have a high-extraction performance relative to many other commonly used extractants, as well as giving good product recovery.…”