Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712-0165, United States.
Anal Chem. 2012 Sep 4;84(17):7393-9. doi: 10.1021/ac301101b. Epub 2012 Aug 14.
We have previously demonstrated up to 5 × 10(5)-fold enrichment of anionic analytes in a microchannel using a technique called bipolar electrode focusing (BEF). Here, we demonstrate that BEF can also be used to enrich a cationic fluorescent tracer. The important point is that chemical modification of the microchannel walls enables reversal of the electroosmotic flow (EOF), enabling cations, instead of anions, to be enriched via an electric field gradient focusing mechanism. Reversal of the EOF has significant consequences on the formation and shape of the region of the buffer solution depleted of charge carriers (depletion zone). Electric field measurements and numerical simulations are used to elucidate the factors influencing the depletion zone. This information is used to understand and control the location and shape of the depletion zone, which in turn influences the stability and concentration of the enriched band.
我们之前已经证明，使用一种称为双极电极聚焦（BEF）的技术，可以将阴离子分析物在微通道中富集 5×10（5）倍。在这里，我们证明 BEF 也可用于富集阳离子荧光示踪剂。重要的一点是，通过对微通道壁进行化学修饰，可以反转电渗流（EOF），从而使阳离子而不是阴离子通过电场梯度聚焦机制进行富集。EOF 的反转对电荷载流子耗尽区域（耗尽区）的形成和形状有重大影响。使用电场测量和数值模拟来阐明影响耗尽区的因素。这些信息用于理解和控制耗尽区的位置和形状，这反过来又影响富集带的稳定性和浓度。
