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

• Two approaches to fabricate polymer monolith with large surface areas were investigated for SPE.
• Extraction performance of these monoliths was compared with polymer particulate adsorbents.
• Large surface area polymer monoliths display a large capacity for small aromatic analytes.
• The monolithic adsorbents demonstrate an extraction performance independent of flow rate.
• The micropores present a size selective extraction for efficient sample purification.

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.