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Plasma functionalization, surface characterization and protein retention of multiple‐sized polymer beads

The surfaces of several types of polymer beads used in solid‐phase extraction processes were modified with functional groups. Porous polystyrene (PS) macrospheres and polyvinylchloride (PVC) microspheres were plasma‐modified in a fluidized‐bed reactor by functionalization with allylamine (AlA) or acrylic acid (AcA). The surface compositions, as measured by XPS, showed the successful incorporation of the functional groups, and the numbers of these groups were assayed by derivatization onto model planar substrates. Furthermore, the influence on the surface Zeta potential of the beads was measured, which showed shifts of ±10 mV at physiological pH by the immobilized amino or carboxylic groups, respectively. A bovine serum albumin–fluorescein conjugate was used in a liquid chromatography system to evaluate the protein retention capacity. The results indicate higher protein retention on plasma‐treated beads with respect to the untreated materials, and on PS when compared to PVC. Particularly high retention is obtained with AlA functionalization at 100 W. Copyright © 2006 John Wiley & Sons, Ltd.