Equivalence-point electromigration acid-base titration via moving neutralization boundary electrophoresis

• Published in: Electrophoresis Vol. 32; no. 9; pp. 1015 - 1024
• Main Authors: Yang, Qing, Fan, Liu-Yin, Huang, Shan-Sheng, Zhang, Wei, Cao, Cheng-Xi
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.04.2011; WILEY‐VCH Verlag
• Subjects: Acid-base titration; agarose; Boundaries; capillary electrophoresis; electrolytes; Electromigration; Electrophoresis; Electrophoresis, Agar Gel - methods; Equivalence; gels; high performance liquid chromatography; hydrochloric acid; Hydrochloric Acid - chemistry; Hydrogen-Ion Concentration; Linear Models; Linearity; Mathematical models; Models, Chemical; Moving reaction boundary; neutralization; nitrogen; Nonlinear Dynamics; potassium chloride; Reproducibility of Results; sodium hydroxide; Sodium Hydroxide - chemistry; Titration; Titrimetry - methods; Volumetric analysis
• ISSN: 0173-0835; 1522-2683; 1522-2683
• DOI: 10.1002/elps.201000415

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 pKa 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.