## 2 Various PPF Strategies
### PPF Based on Photografting  
Surface photografting is an efficient method for the modification of polymer surfaces, invented and developed in the laboratories of Ranby and first published in 1986 by [PERSON] et al. [10]. This process has recently gained popularity in monolith fabrication. For instance, the separation of metal cations was achieved using IDA functionalized organic polymer monolith by capillary high- performance immobilized metal chelate chromatography [11]. In this work a poly (lauryl methacrylate (LMA)-_co_-EDMA) monolith was prepared in UV-transparent fused silica capillary followed by photografting of a poly(GMA) layer on the monolith surface through the benzophenone activated surface following a similar route to that in Scheme 3, (see route II). The difference resides in substituting GMA to 2-acrylamide-2-methyl-1-propanesulfonic acid (AMPS). The grafted monolith was then modified with IDA through the ring opening of the epoxy on the GMA structure according to Route II shown in Scheme 1. The results demonstrated that increasing the concentration of GMA led to an increase in the retention factors of analytes. The proposed monolith was applied to the separation of alkaline earth and transition metal ions in natural and potable waters.  
The photografting of a monolithic capillary column prepared by the in situ co-polymerization of butyl methacrylate (BMA) and EDMA in a binary porogen consisting of 1-decanol and cyclohexanol in the presence of the initiator 2,2-dimethoxy-2-phenylacetophenone (DMPA) has been reported [12]. The prepared monolithic capillaries were subjected to PPF in single- and two-step photografting techniques in the aim of reducing protein adsorption to the monolith of interest (see Scheme 4). In the single step photografting, there are two procedures, the original monolith was flushed with monomer solution without initiator and the other way was to flush the original monolith with monomer solution with initiator and both were exposed to UV irradiation (see Scheme 4). The two-step photografting was obtained by flushing the original monolith first with only initiator and exposed it to UV irradiation, then the obtained monolith was flushed with monomer solution and exposed again to UV irradiation. The adsorption of protein was reduced to less than 2% when using PPF compared to unmodified monolith surface. It has been shown that the single-step without initiator and two-step techniques were more effective than the single-step with initiator. The authors expected that the proposed monolith can be used for multifunctional microanalytical devices.  
Furthermore, PPF via a photografting process has been used to prepare a monolithic capillary for the separation of intact proteins and peptides in two-dimensional liquid chromatography coupled with mass spectrometry [13]. The precursor monolith was prepared via UV photopolymerization of a mixture of BMA and EDMA using cyclohexanol and 1-dodecanol as the porogenic solvents. After polymerization, the monomer 2-acrylamide-2-methyl-1-propanesulfonic acid was grafted to the BMA-_co_-EDMA monolithic capillary in single-step and two-step photografting as described previously to yield a strong cation exchange stationary phase, see Scheme 3. The results showed the successful separation of 11 intact proteins that were obtained within 20 min by implementing a gradient across a limited RPC composition window in the second dimension.  
**Scheme 4.** Scheme of the (**b**) single- and (**a**) two-step photografting procedures. Taken with permission from [12].