Graphene oxide nanoparticles and their influence on chromatographic separation using polymeric high internal phase emulsions

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.