Abstract
A method of chromatographic separation of aminobenzoic acid isomers, in which a sulfonated cation exchange resin Amberlite CG-120, Cu(II) form, was used as a stationary phase and aqueous ammonia as a developer, was investigated.
Studies on the adsorption of the three isomers to the resin in aqueous ammonia showed that (a) the Kd value of each isomer decreased with increasing concentration of ammonia, (b) the Kd value of ο-isomer was much larger than that of m- or p-isomer at a pH range from 8.0 to 10.0 because of the formation of a stable complex and (c) the rate of adsorption and desorption of m-isomer was different from that of ο- or p-isomer probably because of the difference in composition of the complex.
The separation of ο- and m-isomers or of ο- and p-isomers was successfully achieved when a mixture was eluted through a column of φ 14 mm×390 mm with aqueous ammonia of pH 8.4 at a flow rate of 0.3 ml/min., but m- and p-isomers could not be separated except when pure water was used as a developer.
From the studies on the stability of Cu-ο-aminobenzoic acid complex in NaOH solution of pH 10.0, it was found that NaOH solution also was useful as a developer for separating ο- and m- or ο- and p-isomers.
