Equivalence‐point electromigration acid–base titration via moving neutralization boundary electrophoresis

Abstract

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.

Undergraduate laboratory experiment on determination of total protein content in milk powder by moving reaction boundary titration

“…Based on these concepts, Yang et al . and Wang et al . developed the MRBT method and designed the relevant device for acid–base titration analysis.…”

“…The MRBT method was established on the basis of the concept of moving reaction boundary (MRB) electrophoresis [18,19] derived from the ideas of "precipitate reaction front" and "moving reaction front" [20,21]. Based on these concepts, Yang et al [22] and Wang et al [23] developed the MRBT method and designed the relevant device for acid-base titration analysis. Then in 2013, Wang et al [24] and Guo et al [25] advanced the MRBT technique for determination of total protein content in milk.…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

“…This was first applied to CE by Aebersold and Morrison in 1990 and termed dynamic pH junction in 2000 by Britz‐McKibbin et al. , but it is also known as a moving neutralization boundary and is a subcategory of moving reaction boundaries .…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2014–2016)

“…. However, this preconcentration technique is also known as a moving neutralization boundary and is a subset of moving reaction boundaries . Even though the mechanism of dynamic pH junction is well studied, the amount of molecules injected compared to the amount captured by the dynamic pH junction focusing is sometimes not clear.…”