## 2 Various PPF Strategies
### PPF of NAS Based Monoliths  
[PERSON] et al. (2018) reported the study of functionalization of monolithic capillary column using \(N\)-acryloxysuccinimide (NAS) as a functional monomer in the template monolith and various alkylamine ligands were attached to the surface of the NAS-based monolith for RPC. The precursor monolith of poly(NAS-_co_-EDMA) was prepared with NAS and EDMA in toluene as porogen solvent via an in situ photopolymerization in the presence of AIBN. The obtained monolith was then subjected to PPF (see Scheme 16) with alkylamines by flushing the monoliths with alkylamine solutions for 30 min at a flow rate of 1 uL/min. The analysis of Raman Spectra was obtained before and after the PPF process to insure the grafting of the alkylamines to the surface of the monolith. The monolithic capillary columns were evaluated in terms of retention, selectivity and efficiency using alkylbenzenes and PAHs as solute probes in reversed-phase CEC (RP-CEC). The results of the electrochromatography were based, among other things, on the chemical structure of different alkyl chains in the monolith. The same research group continued their investigation on functionalizing monolithic capillary column using NAS and reported shortly after the above investigation, the preparation of hexylamine-functionalized poly(NAS-_co_-EDMA) and its ability to separate aromatic compounds and proteins in CEC ([PERSON] et al., 2018). It was demonstrated that the monolithic capillary columns followed the reversed-phase behavior. The hexylamine-functionalized poly(NAS-_co_-EDMA) were successfully able to separate alkylbenzenes, anilines, amino acids, phenols, organic acids and proteins. Furthermore, the same group reported that the precursor poly(NAS-_co_-EDMA) can be functionalized with chiraly active ligands for chiral capillary chromatography [27]. Propargylamine is one of the alkylamines and was first attached to the surface of the monolith. Then, \(\beta\)-cyclodextrinrin was grafted to the functionalized poly(NAS-_co_-EDMA). The characterization of the monolith was obtained after each synthetic step by using for example, Raman spectroscopy. The enantioseparations of flavanone enantiomers were successfully obtained in both CEC and nano-LC. In another study, the same group focused on functionalizing the surface of microporous monolithic capillary columns with varying aromatic ligands to be used in RP-CEC [28]. A mixture containing NAS and EDMA in toluene solution as porogen and in the presence of AIBN was prepared via in situ photopolymerization to obtain poly(NAS-_co_-EDMA). The next step was to graft the aromatic amines, such as benzylamine, phenylbutylamine and naphthylamine, individually on the surface of the precursor monolith by nucleophilic substitution of N-hydroxysuccinimide esters (see Scheme 17). The obtained functionalized poly(NAS-_co_-EDMA) monoliths were evaluated in terms of resolution, retention and selectivity. It was determined that the small change in the chemical structure of the aromatic selectors as ligands gave different chromatographic results. The immobilization of gold nanoparticles to the surface of poly(NAS-_co_-EDMA) through the thiol-yne click chemistry was also developed [29]. The propargylamine was first attached to the poly(NAS-_co_-EDMA) monolith by nucleophilic substitution and then the cysteamine was grafted to the surface through thiol-yne addition reaction (see Scheme 18). Afterwards, the adsorption of gold nanoparticles to the monolithic surface was performed. This proposed method allowed the design of microdevices containing nanostructure and it can be used in microfluidic chip technology. **Scheme 17. ** Schematic representation of the two-step synthetic pathway applied to prepare poly(\(N\)-acryloxysuccinimide (NAS)-_co_-EDMA) monolith functionalized with varied aromatic selectors: (i) NAS and EDMA are photopolymerized in the presence of toluene as porogen; (ii) aromatic amines are grafted on the surface of the macroporous monolith via nucleophilic substitution of \(N\)-hydroxysuccinimide esters.