## 2 Various PPF Strategies
### Monoliths with GMA Functional Monomers
The precursor poly(GMA-_co_-EDMA) monolith was subjected to PPF with both sodium hydrogen sulfide and cysteine in separate experiments to obtain thiol modified monoliths. The resulted thiol monolithic columns were modified with GNP by passing chloroauric acid within the columns (see route I in Scheme 2). Due to their high affinity toward gold, cysteine containing peptides were effectively and selectively captured by the GNP-modified monoliths. In a continuation set of studies, the same thiol activated precursor poly(GMA-_co_-EDMA) monolith was loaded with colloidal GNP by pumping the suspension through the column (see also route I in Scheme 2). This approach afforded higher surface coverage with GNP than the in situ reduction of chloroauric acid within the column. This type of monolith with bound GNP permit the functionalization of the surface with low molecular weight thiol-containing surface ligands (see routes Ia, Ib, Ic, Id and Ic in Scheme 2). Thus, a single monolithic column would be used in different separation modes. These columns with exchangeable chemistries were demonstrated in CEC, micro- and nano-HPLC separations of peptides and proteins in both RPC and ion exchange modes [6]. The preparation of methacrylate-based diol monoliths for the separation of polar and nonpolar solutes under hydrophilic interaction liquid chromatography (HILIC) and reversed-phase chromatography (RPC) modes in capillary LC was reported [7]. In this work, after copolymerizing GMA and poly (ethylene glycol) dimethacrylate (PEGDMA) in situ in a 150 mm \(\times\) 320 \(\upmu\)m I.D. capillary column, the obtained monolith was flushed with sulfuric acid solution to form diols at the surface of the monolith. The results showed that increasing the GMA content in the monolith led to increasing the monolith hydrophilicity. The poly(GMA-_co_-PEGDMA) monolith was evaluated in the separation of phenol compounds, phthalic acids and polyaromatic hydrocarbons (PAHs). Commonly, the critical compositions of the mobile phases corresponding to the transition from the HILIC to the RPC mode were around 70% acetonitrile in water. The separation of polar analytes, such as phenols and amides, was commonly performed with more than 90% acetonitrile content in the mobile phase to achieve good retention. The critical value of the poly(GMA-_co_-PEGDMA) monolith stationary phase was gained when the content of acetonitrile in the mobile phase exceeded 90%, and for separation of phenols 98% acetonitrile in the mobile phase was needed. This result indicated that this monolith still has low hydrophilicity. In terms of applications of monolith precursors subjected to PPF processes one can cite a poly(GMA-_co_-EDMA) monolithic that was converted to an anion exchange column via PPF with quaternary amine groups through the reaction of the monolith with trimethylamine. The resulting anion-exchange column proved useful for the determination of the low level of bromate in food and drinking water by ion chromatography [8]. The precursor of the anion exchange monolith was based on poly(GMA-_co_-EDMA) prepared via in situ polymerization inside a stainless steel tubing. This method successfully detected bromate after the post reaction and showed good LOD, linearity, short analysis time of 8.5 min and reproducibility. Another application involved the separation of DNA fragments and oligonucleotides on a poly(GMA-_co_-EDMA) precursor monolith prepared in a microbore column that was converted to a weak anion-exchange monolithic bearing diethyl amine ligands via PPF (see route V in Scheme 1) [9]. The prepared monolith demonstrated good potential for the separation of DNA molecules and oligodeoxythymidylic acids and can be used for the rapid separation of biomolecules as well as in various applications in biomedical and pharmaceutical analysis.