Abstract
The chromatographic behavior of saturated aliphatic di- and tricarboxylic acids of C2C8 on the column of strongly basic anion-exchange resin was studied. A 1.1 cmφ×10 cm column of Dowex 1-X8 chloride {(200400)mesh} was used. Acids in the eluate were detected photometrically by means of indicator color developement. The condition of elution was as follows. [Cl-]: 0.2 M, pH 2.0, 4.5, 5.0, 5.5, and 12. Temp.: 30°C. Flow rate: 60 ml/h.
The distribution ratio, Dv, of divalent acid is represented by the equation,
Dv=α0χ0+α1χ1/[Cl-]+α2χ2/[Cl-]2
where α0, α1, and α2 are molar fractions of undissociated molecules, monovalent and divalent ions (here α0+α1+α2=1) respectively, and then χ0, χ1, and χ2 are characteristic coefficients of them, respectively.
The Dv values were given by the elution experiments, then the χ values were calculated according to the above equation.
The behavior of these acids did not essentially differ from that of the fatty acids. However, the abnormality which had been observed in formic acid, spread over from oxalic to glutaric acid in the case of dicarboxylic acid homologs. Especially, the χ2 values of the acids from malonic to adipic acid were practically equal each other, besides, malic and tartaric acid also gave almost equal values, so that the high pH media were not adequate to separation of such acids.
The χ1 values of malonic and methylmalonic acid were extremely higher than those of oxalic and succinic acid. The phenomenon was observed in maleic and citraconic acid in the case of unsaturated acids. This is interesting in relation to the structure of such monovalent ions in aqueous solution.
