A facile route for the chemical functionalisation of polydivinylbenzenes and the application of amphoteric polydivinylbenzene microspheres to the simultaneous solid-phase extraction of acidic and basic drugs from water samples

Mixed-mode ion-exchange sorbents with amphoteric character are intriguing materials because not only can anions and cations be extracted from liquid samples using one single sorbent rather than two (anion extraction under one set of conditions, cation extraction under a second set of conditions), but it may be feasible to establish extraction conditions where anionic and cationic analytes can be extracted simultaneously. In the present study, an unusual but versatile synthetic route was used to install amphoteric character into polydivinylbenzene microspheres produced through precipitation polymerisation. The key synthetic step used for the chemical functionalisation of the polydivinylbenzenes exploited Diels–Alder cycloaddition chemistry to target the pendent styryl groups that are present in polydivinylbenzenes. With maleic anhydride as a dienophile, Diels–Alder cycloaddition yielded polydivinylbenzenes decorated with anhydride moieties. Whilst such materials are interesting in their own right as reactive resins, ring-opening of the polymer-bound anhydride units with ethylenediamine yielded an amphoteric material with both weak anion-exchange (WAX) and weak cation-exchange (WCX) character. This polymer was evaluated as a pH-tuneable sorbent for the solid-phase extraction (SPE) of acidic and basic pharmaceuticals from water samples. Following optimisation of the analytical method including the SPE, the method was subjected to validation and then applied to the extraction and determination of acidic and basic pharmaceuticals present at low concentrations in river water, effluent wastewater and influent wastewater samples. Simultaneous extraction and determination of acidic and basic compounds was found to be achievable, with method quantification limits down to 1 ng L⁻¹.