Guo Xuhong, Kirton Gavin F, Dubin Paul L
Department of Chemistry, Indiana University-Purdue University, Indianapolis, 402 N. Blackford Street, 46202-3274, USA.
J Phys Chem B. 2006 Oct 26;110(42):20815-22. doi: 10.1021/jp062658q.
Carboxylated ficolls were prepared as model spherical colloids of variable charge and size, with radii ranging from 3.0 to 19.3 nm. Capillary electrophoresis (CE), electrophoretic light scattering (ELS), and potentiometric titration were used to determine mobilities as a function of pH, degree of ionization alpha, and surface potential psi(0). Measured mobilities typically display a plateau at high pH, corresponding to high alpha and psi(0), confirming the general nature of this effect for charged spheres, seen also for charged dendrimers and charged latex particles. This result is examined in the context of a discontinuity in mobility predicted by the Wiersema, O'Brien, and White (WOW) theory and a more recent primitive model electrophoresis (PME) theory, in which bound counterions are considered either as point charges or as hard spheres. While no mobility maximum can be determined as expected by these two theories, our data seem more to support Belloni's theoretical expectations on charged polymers and spheres. Here we explain the mobility plateaus in terms of counterions accumulated close to the surface (surface potential-determining ions) or within the shear plane (mobility-determining ions).
羧化聚蔗糖被制备成具有可变电荷和尺寸的球形胶体模型，半径范围为3.0至19.3纳米。采用毛细管电泳（CE）、电泳光散射（ELS）和电位滴定法来测定迁移率与pH值、电离度α和表面电位ψ(0)的函数关系。测得的迁移率通常在高pH值时呈现出一个平台期，对应于高α和ψ(0)，这证实了这种效应对于带电球体的普遍性，在带电树枝状大分子和带电乳胶颗粒中也能看到。在由维瑟马、奥布赖恩和怀特（WOW）理论以及最近的原始模型电泳（PME）理论预测的迁移率不连续性的背景下研究了这一结果，在这些理论中，结合的抗衡离子被视为点电荷或硬球。虽然无法如这两种理论所预期的那样确定迁移率最大值，但我们的数据似乎更支持贝洛尼对带电聚合物和球体的理论预期。在此，我们根据在表面附近积累的抗衡离子（表面电位决定离子）或在剪切面内积累的抗衡离子（迁移率决定离子）来解释迁移率平台期。
