Electrochemically modulated liquid chromatography and the Gibbs adsorption equation.
Electrochemically modulated liquid chromatography and the Gibbs adsorption equation.
复制标题
电化学调制液相色谱和吉布斯吸附方程。
作者：
D. Keller;M. Porter
电化学调制液相色谱法使用导电材料如多孔石墨碳（PGC）作为色谱固定相和工作电极。这种双重功能使得能够通过改变施加到填料的电势（E（app））来操纵分离。因此，通过监测相对于E（app）的保留因子（k '），可以设计用于检查电吸附过程的色谱工具。本文通过检查带电芳族化合物在PGC的保留来开发这种新的能力。吉布斯吸附方程和相关公式（例如，Lippmann方程）用于确定这些溶质在不同支持电解质中的界面过量（γ）、界面张力的变化（dgamma）、电极上的电荷（q（M））和零电荷电位（PZC）。PZC的值也从ln k'对E（app）的图中确定。在这种情况下，ln k'的依赖性揭示了随着电解质浓度增加，随着阴离子的特异性吸附强度的增加，PZC向更阴极值的偏移。总之，这些结果提供了深入了解保留机制，更一般地说，在带电的碳电极吸附。作为探针的带电接口相对于流动相的组成，温度和压力的扩展这一战略进行了简要描述。
Electrochemically modulated liquid chromatography uses a conductive material like porous graphitic carbon (PGC) as a chromatographic stationary phase and a working electrode. This dual functionality enables manipulation of separations by changes in the potential applied (E(app)) to the packing. Thus, by monitoring the retention factor (k') with respect to E(app), a chromatographic tool for examination of electrosorption processes can be devised. This novel capability is developed herein by examining the retention of charged aromatic compounds at PGC. The Gibbs adsorption equation and related formulations (e.g., the Lippmann equation) are used to determine interfacial excesses (Gamma) of these solutes in different supporting electrolytes, changes in interfacial tension (dgamma), the charge on the electrode (q(M)), and the potential of zero charge (PZC). Values of the PZC were also determined from plots of ln k' versus E(app). In this case, the dependence of ln k' reveals a shift in the PZC to more cathodic values as the strength of specific adsorption by anions as the electrolyte concentration increases. Together, these results provide insights into the retention mechanism and, more generally, to adsorption at electrified carbon electrodes. Extensions of this strategy as a probe of electrified interfaces with respect to mobile-phase composition, temperature, and pressure are briefly described.