Laboratory of Bioseparation and Analytical Biochemistry, Key Laboratory of MOE for Microbial Metabolism and School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, P. R. China.
Electrophoresis. 2011 Apr;32(9):1015-24. doi: 10.1002/elps.201000415. Epub 2011 Apr 4.
In this paper, we developed a novel method of acid-base titration, viz. the electromigration acid-base titration (EABT), via a moving neutralization boundary (MNR). With HCl and NaOH as the model strong acid and base, respectively, we conducted the experiments on the EABT via the method of moving neutralization boundary for the first time. The experiments revealed that (i) the concentration of agarose gel, the voltage used and the content of background electrolyte (KCl) had evident influence on the boundary movement; (ii) the movement length was a function of the running time under the constant acid and base concentrations; and (iii) there was a good linearity between the length and natural logarithmic concentration of HCl under the optimized conditions, and the linearity could be used to detect the concentration of acid. The experiments further manifested that (i) the RSD values of intra-day and inter-day runs were less than 1.59 and 3.76%, respectively, indicating similar precision and stability in capillary electrophoresis or HPLC; (ii) the indicators with different pK(a) values had no obvious effect on EABT, distinguishing strong influence on the judgment of equivalence-point titration in the classic one; and (iii) the constant equivalence-point titration always existed in the EABT, rather than the classic volumetric analysis. Additionally, the EABT could be put to good use for the determination of actual acid concentrations. The experimental results achieved herein showed a new general guidance for the development of classic volumetric analysis and element (e.g. nitrogen) content analysis in protein chemistry.
本文提出了一种新的酸碱滴定方法，即电迁移酸碱滴定（EABT），通过移动中和边界（MNR）实现。以 HCl 和 NaOH 分别作为强酸和强碱模型，首次采用移动中和边界法进行了 EABT 实验。实验结果表明：（i）琼脂糖凝胶浓度、所施加的电压以及背景电解质（KCl）的含量对边界移动有明显影响；（ii）在恒定酸和碱浓度下，移动长度是运行时间的函数；（iii）在优化条件下，HCl 的移动长度与自然对数浓度之间存在良好的线性关系，该线性关系可用于检测酸的浓度。实验进一步表明：（i）日内和日间运行的 RSD 值分别小于 1.59%和 3.76%，表明在毛细管电泳或 HPLC 中具有相似的精密度和稳定性；（ii）具有不同 pK(a) 值的指示剂对 EABT 没有明显影响，与经典方法中对等当点滴定判断的强烈影响形成鲜明对比；（iii）EABT 中始终存在恒定的等当点滴定，而不是经典的容量分析。此外，EABT 可用于实际酸浓度的测定。本文的实验结果为经典容量分析和蛋白质化学中元素（如氮）含量分析的发展提供了新的普遍指导。
