Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617.
Langmuir. 2012 Jan 10;28(1):1013-9. doi: 10.1021/la203245n. Epub 2011 Nov 29.
The Joule heating effect is inevitable in electrophoresis operations. To assess its influence on the performance of electrophoresis, we consider the case of a charge-regulated particle in a solution containing multiple ionic species at temperatures ranging from 298 to 308 K. Using an aqueous SiO(2) dispersion as an example, we show that an increase in the temperature leads to a decrease in both the dielectric constant and the viscosity of the liquid phase, and an increase in both the diffusivity of ions and the particle surface potential. For a particle having a constant surface potential, its electrophoretic mobility is most influenced by the variation in the liquid viscosity as the temperature varies, but for a charged-regulated particle both the liquid viscosity and the surface potential can play an important role. Depending upon the level of pH, the degree of increase in the mobility can be on the order of 40% for a 5 K increase in the temperature. The presence of double-layer polarization, which is significant when the surface potential is sufficiently high, has the effect of inhibiting that increase in the mobility. This implies that the influence of the temperature on the mobility of the particle is most significant when the pH is close to the point of zero charge.
焦耳加热效应在电泳操作中是不可避免的。为了评估其对电泳性能的影响，我们考虑了在 298 到 308 K 温度范围内含有多种离子物种的溶液中带电荷调节的粒子的情况。以水合二氧化硅分散体为例，我们表明，温度的升高会导致液相介电常数和粘度降低，而离子扩散系数和粒子表面电势增加。对于具有恒定表面电势的粒子，其电泳迁移率受温度变化时液相粘度变化的影响最大，但对于带电荷调节的粒子，液体粘度和表面电势都可以发挥重要作用。根据 pH 值的高低，温度升高 5 K 时，迁移率的增加幅度可达 40%左右。当表面电势足够高时，双电层极化的存在会抑制迁移率的增加。这意味着当 pH 值接近零电荷点时，温度对粒子迁移率的影响最为显著。
