In situ prepared MIP monoliths

Thus far, the most successful approach to M IP-based CEC utilises capillary columns filled with a monolithic, super-porous imprinted polymer [39-41]. The morphology of a certain MIP monolith is depicted in Fig. 16.3. Using this system enantiomer separations with baseline resolution have been carried out in less than 2 minutes. The M IP-filled capillaries are obtained by an in situ photo-initiated polymerisation process (Fig. 16.4]. The capillary is filled with a pre-polymerisation mixture of imprint molecule, functional and cross-linking monomers (MAA and TRIM, respectively), radical initiator (2,2 -azobisisobutyronitrile) and solvent (toulene). Both ends of the capillary are sealed and the polymerisation is performed 

In a slightly modified approach, the MIPs can be rendered super-porous by the use of 1-25% iso-octane as a porogenic agent [40,41]. The porogen is composed of a mixture of solvents in which the porogenic agent (iso-octane) acts as a bad solvent for the growing polymer chains, while the other solvent (toluene for 

Capillary with sealed ends and covered detection a 

Regarding the detection protocols used with capillary columns with molecularly imprinted stationary phases, on-column UV absorbance detection has been exclusively used. Some sort of open tubular area without imprinted polymer is normally prepared to perform detection. It has been shown, however, that UV detection can be performed through the imprinted polymer [39] in some cases. A nice feature with the photo-induced polymerisation procedure is that a part of the capillary column can be covered during the polymerisation reaction, thus preventing polymer being formed in that area. This is utilised to readily prepare detection windows on the MIP capillary columns. There is then no need for coupling of a second capillary to the imprinted polymer-filled capillary to be able to perform detection. 

Another approach to monolithic imprinted polymer capillary columns has been reported. The polymerisation was performed at 60°C and thus thermally initiated [70,71]. The result is a dense polymer inside the whole capillary. The resulting MIP capillary then has to be connected to an electrolyte-filled open capillary via a teflon tube and a detection window is prepared on the open capillary to facilitate detection (as described above. Fig. 16.2). Also, ammonium acetate (1-2 mM) is added as a conducting agent to the pre-polymerisation mixture. This is done to allow exchange of the solvent of polymerisation for electrolyte, which can be achieved electrophoretically by stepwise increase of the electric field until a stable base-line is obtained. 

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