Characterization of large surface area polymer monoliths and their utility for rapid, selective solid phase extraction for improved sample clean up

While polymer monoliths are widely described for solid phase extraction (SPE), appropriate characterization is rarely provided to unravel the links between physical characteristics and observed advantages and disadvantages. Two known approaches to fabricate large surface area polymer monoliths with a bimodal pore structure were investigated. The first incorporated a high percentage of divinyl benzene (PDVB) and the second explored hypercrosslinking of pre-formed monoliths. Adsorption of probe analytes; anisole, benzoic acid, cinnamic acid, ibuprofen and cortisone were investigated using frontal analysis and the SPE performance was compared with particulate adsorbents. Frontal analysis of anisole described maximum adsorption capacities of 164 mg g⁻¹ and 298 mg g⁻¹ for hypercrosslinked and PDVB adsorbents, respectively. The solvated state specific surface area was calculated to be 341 and 518 m² g⁻¹ respectively. BET revealed a hypercrosslinked surface area of 817 m² g⁻¹, 2.5 times greater than in the solvated state. The PDVB BET surface area was 531 m² g⁻¹, similar to the solvated state. Micropores of 1 nm provided the enhanced surface area for hypercrosslinked adsorbents. PDVB displayed a pore size distribution of 1–6 nm. Frontal analysis demonstrated the micropores present size exclusion for the larger probes. Recovery of anisole was determined by SPE using 0.4 and 1.0 mL min⁻¹. Recovery for PDVB remained constant at 90% ± 0.103 regardless of the extraction flow rate suggesting extraction performance is independent of flow rate. A more efficient sample purification of saccharin in urine was yielded by PDVB due to selective permeation of the small pores.