Extraction of organic acids by ion-pair formation with tri-n-octylamine : Part 4. Influence of organic phase composition

Synthetic food dyes are extracted by ion-pair formation with tri-n-octylamine. Mixed organic phases are used, consisting of mixtures of hexane with one of the following solvent modifiers: chloroform, dichloromethane, methyl isobutyl ketone, butyl acetate or pentanol. Logarithmic plots of the distribution ratio versus the volume fracton of the solvent modifier are linear for dichloromethane, chloroform and pentanol. The efficiency of the solvents is classified as follows: dichloromethane > pentanol > chloroform > methyl isobutyl ketone > butyl acetate > hexane. The addition of pentanol to chloroform provides nearly quantitative recovery for hydrophilic solutes.