Non-invasive determination of ionizable ligand group density on high internal phase emulsion derived polymer

Tubular Catalytic Polyhipe Reactor with Deposited Silver Nanoplate Nanoparticles

“…Positively charged quaternary amine (QA) groups were selected, due to a negative zeta potential of silver nanoparticles around neutral pH and above [86]. Although the modification procedures for the conversion of epoxide groups into QA groups are already well established [71], the precise determination of their amount in a noninvasive manner was introduced rather recently [71,87,88]. The determination is based on the pH transition using two mobile phases with the same pH but different ionic strength [87,89].…”

“…When the groups present on a matrix have an ionizable character, they are titrated during the stepwise buffer exchange and cause a pH shift. It was demonstrated that the duration and height of the pH transition shift is linearly proportional to the amount of ionizable groups [71,88].…”

“…PolyHIPE monoliths with a matrix volume of approximately 0.5 ml were prepared and characterized for permeability and open porosity as described elsewhere [11,21]. Briefly, the epoxy groups of the polyHIPE polymer were converted to quaternary amine (QA) ionizable functional groups with a basic aqueous solution of TMAHC [71]. Different molar concentrations of TMAHC, namely 0.01, 0.1, 0.15 M, were adjusted to pH 11 with NaOH.…”

“…The amount of QA groups present on the functionalized polyHIPE-QA was determined with a pH transition method as described in the literature [71]. Briefly, the measurements were performed on a highperformance liquid chromatography system ( ÄKTA HPLC, Sweden) at a flow rate of 3 ml/min.…”

“…The buffers used were 5 mM Tris/NaOH, pH 9.6 (buffer A) and 5 mM Tris/NaOH, 1 M NaCl, pH 9.6 (buffer B). By changing the buffers stepwise, the pH transitions were obtained and the calibration curve from the literature [71] was used to calculate the QA group concentration.…”