Analytical use of solvent extraction with acetonitrile/water/chloroform and 1-propanol/water/cyclohexane mixtures

To obtain an organic phase containing acetonitrile or 1-propanol from aqueous acetonitrile or aqueous 1-propanol solution, the effect of chloroform and cyclohexane as auxiliary solvents has been investigated. Use of such ternary systems offers an alternative to the so-called salting-out method, in which inorganic salts or hydrophilic organic materials are used to separate organic phases from otherwise miscible solvent mixtures. It also seems preferable for solvent-extraction procedures, since only a small amount of auxiliary solvent is needed instead of the usually large amount of a salt (impurities in which may cause undue contamination); also, the volume and composition of the organic phase can be predicted from phase diagrams and the overall composition of the solvent mixture. Volume-fraction diagrams are especially easy to use. Furthermore, equilibrium is attained in solvent mixtures more rapidly than in salting-out systems. The utility of the ternary solvent systems has been demonstrated for extraction of intermediate molybdophosphate complexes which are specifically formed in aqueous acetonitrile solutions.