Polymer monolith-integrated multilayer poly(dimethylsiloxane) microchip for online microextraction and capillary electrophoresis

We reported the in situ synthesis and use of porous polymer monolith (PPM) columns in an integrated multilayer PDMS/glass microchip for microvalve-assisted on-line micro-extraction and microchip electrophoresis for the first time. Under the control of PDMS microvalves, the grafting of the microchannel surface and in situ photopolymerization of poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith in a defined zone were successfully achieved. Different factors including the surface grafting, polymerization time, PDMS elastic properties (ratio of oligomer/curing reagent) and UV intensity that affect the monolith synthesis in the PDMS microchannel were investigated and optimized. Dopamine, a model analyte, has been online microextracted, eluted, electro-phoresized and electrochemically detected in the microchip, with a mean concentration enrichment factor of 80 (n = 3). The results demonstrated that the PPM could be synthesized successfully in the PDMS microchip with a homogeneous structure and excellent mechanical properties. Furthermore, owing to the intrinsic character using PDMS in large-scale integrated microsystems, the implantation of PPM pretreatment units in PDMS microchips would make it possible to deal with complicated analytical processes in a high-throughput way.