The use of photopolymers as retaining frits and monoliths for electrochromatography in capillaries or microfluidic devices and some selected applications.

摘要

This work explores the use of two different organic photopolymers for electrochromatography in the capillary format and also demonstrates their incorporation into a microfluidic platform. The first photopolymer studied functioned as a retaining frit for silica-supported, microparticulate stationary phase. After using the photopolymerization procedure in the capillary format the retaining frits were successfully integrated into the microfluidic platform. However, packing the microfluidic device with stationary phase particles could not be accomplished. A second photopolymer possessing C4-functionalities was therefore investigated as a porous stationary phase. It could be incorporated as a monolith in capillaries and thereby avoided the packing difficulties associated with individual particles and polymer retaining frits. Six polyaromatic hydrocarbons were baseline-separated within two minutes on this monolithic column. The monolith was also successfully created in the microfluidic format as verified by the separation of two fluorescent dyes. Due to the high cost of microfluidic devices the properties of the monolith were studied primarily in the capillary format. Van Deemter plots revealed the potential to use high mobile phase velocities without sacrificing resolution. Hydrodynamic and electrokinetic flow measurements gave insights into the porosity and tortuosity of the polymer by non-destructive means. Additionally, scanning electron microscopy and atomic force microscopy were employed to elucidate the microscopic structure and evaluate the pore size. The dependence of the electroosmotic flow on percentage and type of organic solvent, pH, ionic strength and concentration of sulfonate moieties in the polymer was measured. Various applications were surveyed with an emphasis on the separation of proteins. Their separation also served to evaluate the manufacturing process in terms of inter- and intra-capillary reproducibility. By comparing capillary electrochromatography, capillary electrophoresis and micro-LC it was found that chromatography is not the major contributor to the overall CEC separation of proteins. However, the monolithic columns demonstrated very good reproducibility as could be seen by using serum proteins as probes. Separations of small molecules were shown to be greatly based on a chromatographic separation mechanism. These applications included quality assessment in the synthesis of anthracene-2;3-dialdehyde, the separation of oligonucleotides and the separation of non-steroidal anti-inflammatory drugs.