Recursion approach for moving neutralization boundary formed on IPG strips Part I: With strong alkali rehydration buffer

Abstract

Moving neutralization boundary (MNB) is an important foundation to understand and improve IEF. However, there are obstacles in theoretical predictions of MNB on IPG strips due to the unknown local concentrations of carrier ampholytes on commercial IPG strips and the time-varying boundary velocities. We introduce a recursion approach to extend the current MNB theories into the space-time varying MNB system. The recursion approach emphasizes the localizability of physicochemical parameters in the discrete time intervals and local positions in Lagrangian coordinates, such as local concentrations of carrier ampholytes, local OH concentrations, local boundary velocities, local judgments, etc. The boundary-position recursion equation in a complete time sequence was presented to quantitatively predict the MNB position-time curves by distinguishing three kinds of titration cases according to NaOH concentrations in rehydration buffers. The theoretical position-time curves and local relative judgments of boundaries were satisfactorily validated by corresponding images of boundary migrations achieved from the IPG-MNB experiments with the some typical NaOH concentrations-bromophenol blue-rehydration buffers on pH 4-7 IPG strips. The results achieved herein have evident significances to the development of moving reaction boundary and IEF.

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

“…The reaction led to the formation of MNB. There was always a 1:1 equivalence-point chemical reaction between the H 1 and OH À in the EABT system whether the boundary moved toward the the anode or the cathode, or remained stationary [23,24]. Furthermore, such an equivalence-point reaction between the H 1 and OH À is present in the EABT system at any time.…”

“…The concept of MRB is very useful in the field of electrophoresis. For example, the dynamic theory of isoelectric focusing (IEF) has been well developed from the concept of MNB [23,24,29]. It has been revealed that (i) IEF is based on the physical chemical model of MNB [23,24,29] and (ii) a series of historic issues (viz.…”

“…For example, the dynamic theory of isoelectric focusing (IEF) has been well developed from the concept of MNB [23,24,29]. It has been revealed that (i) IEF is based on the physical chemical model of MNB [23,24,29] and (ii) a series of historic issues (viz. pH gradient drifting and plateau during run of IEF, Hjerten's mobilization of pH gradient after run of IEF, and IEF run without carrier ampholytes) can be quantitatively illuminated by the theory of MNB [23,24,29,30].…”

“…It has been revealed that (i) IEF is based on the physical chemical model of MNB [23,24,29] and (ii) a series of historic issues (viz. pH gradient drifting and plateau during run of IEF, Hjerten's mobilization of pH gradient after run of IEF, and IEF run without carrier ampholytes) can be quantitatively illuminated by the theory of MNB [23,24,29,30]. Second, the method of MNB has been used for the sample stacking of zwitterions (viz.…”

“…At the same time, Deman [21,22] observed the elution displacement of metal ions and the separation of six rare earth ions in his experiments. In 1990s, the idea of equivalent electromigration reaction between H 1 and OH À was developed for protein concentration [23]. During the last decade, Cao et al [24][25][26][27] advanced systemic theories and methods of MRB, such as moving precipitate boundary [24], neutralization boundary (MNB) [24][25][26], chelation boundary (MCB) [24,27] and affinity boundary [28].…”