有机酸在阴离子交换树脂上的保留行为及其机理

Study on the Retention Behaviour and Mechanism of Organic Acids on an Anion Exchanger

研究了有机酸在阴离子交换树脂上的保留行为。首次报道了有机酸在阴离子交换色谱过程中的“多峰现象”，即一种有机酸有两个或两个以上的色谱峰流出色谱柱。对这种“多峰现象”形成的机理进行了初步探讨，提出了有机酸离解后的不同价数阴离子在阴离子交换树脂上同时保留的机理。研究中还发现离解很弱的有机酸的保留行为不完全符合离子交换机理。

The retention behaviour and mechanism of organic acids on an anion exchange column Shim pack IC A1 (Shimadzu, Japan) have been studied. The retention valences (x) of organic acids on the anion exchanger were measured based on the following equation:logk′=-(x/y)log〔Eluent〕+constantBy using the linearity of logk′ υs log〔Eluent〕 and the retention valences, the retention mechanisms of organic acids can be predicted. Acetic acid eluted as the non dissociated form by a non ion exchange mechsnism, because its retention valence was only 021. In this work, the multi peak for one organic acid was observed. The chromatograms of citric acid obtained using PyA eluent with different concentration were showed. Two peaks were observed. As eluent concentration decreased, the detection sensitivity (peak area) was increased due to the decrease of the background conductivity. The multiple peaks of citric acid were also observed when the mixture of phthalic acid(PhA) and trihydroxymethylaminomethane (TRIS) was used as eluent. The multi peaks for one organic acid result from the fact that different forms of the organic acid can be separated each other on anion exchanger by ion exchange mechanism. The two peaks of citric acid were caused by separation of mono and divalent citrate anion.