Absorption properties of monolithic poly (divinylbenzene-co-N-vinylpyrrolidone) over a wide range of monomer ratios

Abstract

The hydrophilic-lipophilic balance (HLB) polymers are able to directly extract polar and non-polar analytes from the aqueous samples, making them very popular for analytical separation and SPE applications. However, the commonly used suspension polymerization method for preparing HLB polymers is only able to efficiently prepare HLB polymers with low or medium mol percentages of the hydrophilic monomer due to the hydrophilic monomer partitioning into the aqueous phase at higher concentrations. Thus, in this study a series of HLB polymers based on divinylbenzene (DVB) (hydrophobic) and N-vinylpyrrolidone (NVP) (hydrophilic) of widely varying hydrophilicities were prepared by the more robust monolith polymerization method. The monolith polymerization enabled the preparation of DVB-co-NVP polymer from low to high NVP percentages (0 mol% to 55 mol% NVP). The comparative adsorption and separation properties of the series of DVB-co-NVP polymer were assessed using three analytes of varying polarity: adenosine (log P = −1.5), caffeine (log P = −0.07) and p-toluidine (log P = 1.39). Interestingly, the highest binding capacity for binding polar analytes was observed for the monolith polymer prepared with the intermediate 30:70 feed ratio of NVP/DVB, due to an optimal balance of surface area and hydrophilicity. Whereas, for the separation of the non-polar analytes such as p-toluidine from polar analytes like caffeine or adenosine, the hydrophobic polymers containing the lower percentages of the polar monomer (20 mol% NVP) were superior.