The effect of blob size and network dynamics on the size‐based separation of polystyrenesulfonates by capillary electrophoresis in the presence of entangled polymer solutions

Abstract

This work focuses on the separation of standard polystyrenesulfonates (PSS), with molecular masses (Mr) between 16 and 990 x 10(3) in capillaries filled with semidilute (entangled) linear hydrophilic polymers. Contrary to cross-linked chemical gels, which produce permanent networks, solutions of linear polymers lead to dynamic networks. The analytical performances and migration mechanisms are discussed on the basis of experiments performed in solutions of linear polyethyleneoxides and derivatized celluloses of various molecular masses. The influence of the mesh size and of the lifetime of the obstacles of the separating network has been investigated in detail. The mesh size is assimilated to the blob size of the separating polymer and is a decreasing function of its concentration. The lifetime of the obstacles of the network, identified with the reptation time of the polymer chain, characterizes its dynamics. This characteristic time increases with both the molecular weight of the separating polymer and its concentration. Its impact was first examined at fixed blob size. Then, the influence of the blob size was studied while keeping the reptation time of the network constant. By doing so, the existence of interactions between the solute and the separating polymer or between the solute and capillary wall can be more safely assessed. It appears that the reptation time of the mesh has a large influence on the electrophoretic mobility of the PSSs under a threshold value, which is of the order of magnitude of the time taken by the PSS to migrate on the blob size. Also shown are separations using networks made up with mixtures of polyethyleneoxides of the same nature and same mass concentration, but of very different molecular masses. This latter approach allows one to adapt the viscosity of the solution and the dynamics of the network, keeping the blob size constant.

Separation of double-stranded and single-stranded DNA in polymer solutions: I. Mobility and separation mechanism

“…Following the argument by Cottet et al (see Fig. 2 of [16]), this indicates that even for short chain pDMA, at 1% the ªthreshold valueº is already reached, above which the reptation of the polymer ceases to affect the separation. The situation is slightly different under denaturing conditions (Fig.…”

“…The reptation time of the matrix polymers, however, remains the same. According to Cottet et al [16], the network dynamics has an influence on the separation when the reptation time of the polymer is smaller than the renewal time of the analyte, which could be the case here. Another explanation could be given using the concept of constraint release: The Kuhn length b D for ssDNA is much smaller than for dsDNA, so that the first term in Eq.…”

“…For ideal chains (a = 0.5; no excluded volume), b becomes zero and we regain F = F 0 . Following Cottet et al [16], Eq. (1) can be rewritten to:…”

“…2 ) with b = (2a±1)/3 and F 0 being 2.5´10 23 mol ±1 for uncharged polymers [13,16]. For ideal chains (a = 0.5; no excluded volume), b becomes zero and we regain F = F 0 .…”

“…The influence of network dynamics on size-based electrophoretic separation has been studied in more detail by Cottet et al [16]. Estimating the reptation time of the matrix polymer, they found that a threshold value exists below which the electrophoretic mobility of the analyte is influenced by the polymer motion.…”