Hayes M A
Department of Chemistry and Biochemistry, Arizona State University, P.O. Box 871604, Tempe, Arizona, 85287.
Anal Chem. 1999 Sep 1;71(17):3793-8. doi: 10.1021/ac990301v.
Control of electroosmosis by an applied external voltage field in capillary electrophoresis has been limited to buffer pH approximately 5 or below. This poor control at higher pH is caused by a high density of surface charge induced by chemical equilibrium overwhelming the influence of the external voltage-induced charges within the electric double layer. A tert-butyldiphenylchlorosilane treatment was used on fused-silica capillaries to minimize chemically generated ζ-potential where this treatment allowed for control of electroosmosis over a large pH range (2-10). Blocking the surface with traditional polymer-based surface treatments does not work in this application since the polymers increase the viscosity within the electric double layer and impede electroosmosis. The surface created by this reaction is demonstrated in extremely narrow capillaries, down to 2-μm internal diameter. The treated surface is sterically hindered against acid- and base-catalyzed degradation reactions typically associated with organosilanes. This results in a surface that was stable to experimental buffer pH extremes, from pH 3 to pH 10, and was stable for at least 8 weeks exposed to both solution and air.
在毛细管电泳中，通过施加外部电压场来控制电渗作用一直局限于缓冲液pH值约为5或更低的情况。在较高pH值下控制不佳是由于化学平衡诱导的高表面电荷密度压倒了双电层中外部电压诱导电荷的影响。对熔融石英毛细管采用叔丁基二苯基氯硅烷处理，以尽量减少化学产生的ζ电位，这种处理使得在较大的pH范围（2 - 10）内能够控制电渗作用。用传统的基于聚合物的表面处理方法来封闭表面在这种应用中不起作用，因为聚合物会增加双电层内的粘度并阻碍电渗作用。这种反应产生的表面在内径低至2μm的极细毛细管中得到了验证。处理过的表面在空间上阻碍了通常与有机硅烷相关的酸催化和碱催化降解反应。这导致表面在极端的实验缓冲液pH值（从pH 3到pH 10）下稳定，并且在暴露于溶液和空气的情况下至少8周保持稳定。
