Visible light initiated polymerisation of styrenic monolithic stationary phases using 470 nm light emitting diode arrays

摘要

Poly(styrene-co-divinylbenzene) monolithic stationary phases have been synthesised for the first time by photoinitiated polymerisation. An initiator composed of (+)-S-camphorquinone/ethyl-4-dimethylaminobenzoate/N-methoxy-4-phenylpyridinium tetrafluoroborate was activated using a 470 nm light emitting diode array as the light source. Spatially controlled polymerisation of styrenic monoliths has been achieved within specific sections of a 100 µm i.d. polytetrafluoroethylene (PTFE)-coated fused silica capillary using simple photo-masking. The sharpness of the edges was confirmed by optical microscopy, while scanning electron microscopy was used to verify a typical porous, globular morphology. Flow resistance data was used to assess the permeability of the monoliths and they were found to have good flow through properties with a flow resistance of 0.725 MPa cm⁻¹ at 1 µl min⁻¹ (water, 20°C). Conductivity profiling along the length of the capillary was used to assess their lateral homogeneity. Monoliths which were axially rotated during polymerisation were found to be homogeneous along the whole length of the capillary. The monolithic stationary phases were applied to the reversed phase gradient separation of a mixture of proteins. Column fabrication showed excellent reproducibility with the retention factor (k) having a RSD value of 2.6% for the batch and less than 1.73% on individual columns.