Horváth Krisztián, Hajós Péter
Department of Analytical Chemistry, University of Veszprém, Veszprém H-8201, P.O. Box 158, Hungary.
J Chromatogr A. 2006 Feb 3;1104(1-2):75-81. doi: 10.1016/j.chroma.2005.11.064. Epub 2005 Dec 7.
A retention model based on stoichiometric approach has been developed in order to describe analyte retention of anions on latex-based pellicular ion exchanger. The chromatographic process entails two stepwise and complex equilibria, first is ion-pair forming of analyte or eluent ion with ion-exchange sites under the effect of electrostatic forces due to the sulfonic layer behind the aminated functional groups of stationary phase. Second component is the ion-exchange between the analyte and eluent ions. As a new parameter of the fractional electrostatic coefficient of the ion exchange capacity was introduced to develop retention profiles of anions. Analysis of the dependence of the capacity factors on the eluent concentrations at different values of fractional coefficient shed light on the possible complex mechanism. Extensive experimental retention data were obtained for 14 anions (formate, acetate, propionate, pyruvate, lactate, chloride, nitrate, oxalate, malonate, succinate, tartarate, fumarate, maleate, sulphate) using hydroxide eluents of varying concentration. The ion-pair formation and ion-exchange selectivity constants for analyte and eluent species are determined using derived retention equation from experimental data by nonlinear iterative calculation. The model was utilized to predict retention data under elution conditions of practical importance. The predicted and obtained retention factors are in good agreement, which confirms the predictive power of the model.
为了描述阴离子在基于乳胶的薄壳型离子交换剂上的分析物保留情况，已开发出一种基于化学计量学方法的保留模型。色谱过程涉及两个逐步且复杂的平衡，首先是在固定相胺化官能团后面的磺酸层产生的静电力作用下，分析物或洗脱剂离子与离子交换位点形成离子对。第二个部分是分析物与洗脱剂离子之间的离子交换。作为一个新参数，引入了离子交换容量的分数静电系数来绘制阴离子的保留曲线。分析在不同分数系数值下容量因子对洗脱剂浓度的依赖性，揭示了可能的复杂机制。使用不同浓度的氢氧化物洗脱剂，获得了14种阴离子（甲酸根、乙酸根、丙酸根、丙酮酸根、乳酸根、氯离子、硝酸根、草酸根、丙二酸根、琥珀酸根、酒石酸根、富马酸根、马来酸根、硫酸根）的大量实验保留数据。通过非线性迭代计算，利用从实验数据导出的保留方程，确定了分析物和洗脱剂物种的离子对形成常数和离子交换选择性常数。该模型用于预测实际重要洗脱条件下的保留数据。预测的保留因子与获得的保留因子吻合良好，这证实了该模型的预测能力。
