Graphene Oxide Nanoparticles and Their Influence on Chromatographic Separation Using Polymeric High Internal Phase Emulsions

Abstract

This work presents the first instance of reversed-phase liquid chromatographic separation of small molecules using graphene oxide nanoparticle-modified polystyrene-divinylbenzene polymeric high internal phase emulsion (GONP PS-co-DVB polyHIPE) materials housed within a 200-µm internal diameter (i.d.) fused silica capillary. The graphene oxide nanoparticle (GONP)-modified materials were produced as a potential strategy to increase both the surface area limitations and the reproducibility issues observed in monolithic stationary phase materials. GONP PS-co-DVB polyHIPEs were found to have a surface area up to 40% lower than unmodified polymeric high internal phase emulsion (polyHIPE) stationary phases. However, despite having a surface area significantly lower than that of the unmodified material, the GONP-modified polyHIPEs demonstrated superior analyte adsorption properties. Reducing the GONP material did not have any significant impact on elution order or retention factor of the analytes, which was most likely due to low GONP loading attributed to the 250-nm GONPs utilised. The lower surface area of GONP-modified polyHIPEs provided similar separation efficiency and increased repeatability from injection to injection resulting in % relative standard deviations (%RSDs) of less than 0.6%, indicating the potential offered by graphene oxide (GO)-modified polyHIPES in flow through applications such as adsorption or separation processes.

Recent advances in separation applications of polymerized high internal phase emulsions

“…Various porous materials as stationary phases have been widely used and exhibited excellent performance in chromatographic separation [3]. PolyHIPEs as stationary phase exhibited higher permeability in comparison with other porous materials, such as organic polymer, inorganic zeolites, and MOFs, and thus have been applied in chromatographic separation such as CEC [73, 90, 91], TLC [74], nano‐liquid chromatography (nano‐LC) [92], and HPLC [76, 93, 94]. The chromatographic separation performance of polyHIPE monoliths mainly depended on the molecular sieving effect, van der Waals interactions, and the special group interactions (e.g., π‐π interaction, hydrogen‐bonding interactions), therefore, the pore size and distribution of polyHIPEs should be carefully controlled in confined spaces, and the higher shearing stress in HIPEs preparation was deemed to be better for the resulting polyHIPEs, providing a narrower void size distribution and improved homogeneity [95].…”

Effect of shearing stress on the radial heterogeneity and chromatographic performance of styrene-based polymerised high internal phase emulsions prepared in capillary format

“…These results are particularly concerning as the use of low shear mixers for the preparation of poly(HIPE)s for separation science is popular, with most reports utilising shear rates in the order of 300 rpm, [16][17][18][19][20]29,30 as this typically affords larger void and window sizes, allowing high permeabilities to be achieved. However, it is apparent that when these materials are prepared using capillaries with internal diameters less than 540 mm signicantly different structures are obtained compared to the bulk material, with the capillary i.d.…”

“…27 However, their application as stationary phases for liquid chromatography (LC) using typical HPLC housing has so far been limited. 17,18,20,[28][29][30] For example, Yao et al 17 prepared poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [poly(GMA-co-EGDMA)] poly(HIPE)s in 4.6 mm internal diameter (i.d.) stainless steel columns for the anion-exchange separation of proteins, while Choudhury et al 20 prepared poly(styrene-codivinylbenzene) [poly(Sty-co-DVB)] poly(HIPE)s in 1 mm i.d.…”

“…16,17,28 In addition, relatively few reports have focused in depth on the inuence of the poly(HIPE)s structure on the chromatographic performance. 16,30 Of the reports currently available in the literature, only a handful have investigated the preparation of poly(HIPE)s in capillary format, 18,28,29 which is an extremely attractive format for chromatography due to lower sample and solvent consumption and the reduction of peak broadening as a result of radial diffusion. 33 For example, Tunç et al 18 prepared poly(HIPE)s based on isodecylacrylate and DVB in 100 mm i.d.…”

“…capillaries. 29 These reports only focused on the separation of alkylbenzenes, which are relatively small molecules and are known to be problematic for conventional polymer monoliths. 34 To the best of our knowledge there exist no examples for the separation of larger molecules, such as proteins, for poly(HIPE)s prepared in capillary format.…”