A sol-gel-modified poly(methyl methacrylate) electrophoresis microchip with a hydrophilic channel wall

A sol-gel method was employed to fabricate a poly(methyl methacrylate) (PMMA) electrophoresis microchip that contains a hydrophilic channel wall. To fabricate such a device, tetraethoxysilane (TEOS) was injected into the PMMA channel and was allowed to diffuse into the surface layer for 24 h. After removing the excess TEOS, the channel was filled with an acidic solution for 3 h. Subsequently, the channel was flushed with water and was pretreated in an oven to obtain a sol-gel-modified PMMA mi-crochip. The water contact angle for the sol-gel-modified PMMA was approximate to 27.4 degrees compared with approximate to 66.3 degrees for the pure PMMA. In addition, the electro-osmotic flow increased from 2.13 x 10(-4) cm(2) V-1 s(-1) for the native-PMMA channel to 4.86 x 10(-4) cm(2) V-1 s(-1) for the modified one. The analytical performance of the sol-gel-modifiedPMMA microchip was demonstrated for the electrophoretic separation of several purines, coupled with amperometric detection. The separation efficiency of uric acid increased to 74 882.3 m(-1) compared with 14730.5 m(-1) for native-PMMA microchips. The result of this simple modification is a significant improvement in the performance of PMMA for microchip electrophoresis and microfluidic applications.