Separation of sugar by solvent extraction with phenylboronic acid and trioctylmethylammonium chloride

In this paper the solvent extraction of sugar with an ion-pair of boronate anion and quaternary ammonium cation was carried out. Extraction reactions were formulated, and extraction equilibrium constants were obtained based on experimental results. Extraction equilibrium constants, Kf, of extraction of glucose and xylose were higher than those of arabinose, fructose, galactose, mannose, and fucose. We measured the stability constant KS, between phenylboronic acid and sugars in the aqueous solution to clarify the dominant factor involved in the extraction reaction. The order of KS values did not correspond to Kf values. This suggests that the lesser ability of 1,3-trans-diol for ion-pair formation with trioctylmethylammonium and the instability of the ion-pair complex in the organic phase due to steric hindrance contribute mainly to the extraction reaction.