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Esterification‐coupled extraction of organic acids: Partition enhancement and underlying reaction and distribution equilibria

1989; Wiley; Volume: 34; Issue: 7 Linguagem: Inglês

10.1002/bit.260340705

1097-0290

M. Raquel Aires‐Barros, Joaquim M. S. Cabral, Richard C. Willson, Jonas Hamel, C. L. Cooney,

Analytical Chemistry and Chromatography

A novel means of extracting carboxylic acids from aqueous solutions is described which involves the use of a lipolytic enzyme to convert the acid to a more hydrophobic ester. A water-immiscible long-chain alcohol serves both as a reactant in esterifying the acid, and as a solvent for extraction of the ester. Radiochemical tracer studies of the underlying reaction and extraction equilibria established that a low equilibrium concentration of ester (0.04-0.5mM) in the presence of water is counterbalanced by the high distribution coefficient of the ester (220-3380, wt. basis). The net result is a substantial (4- to 15-fold) increase in the apparent distribution coefficient of the acid; 80%-95% of the extracted acid is in the esterified form. The method is applicable to a variety of alcohols and acids.