Extraction of β-blockers from urine with a polymeric monolith modified with 1-allyl-3-methylimidazolium chloride in spin column format

A glycidyl methacrylate-based monolith was modified with an imidazolium-based ionic liquid (IL) for use as a stationary phase in solid-phase extraction (SPE). The monolithic support was prepared via in-situ UV polymerisation in a spin column format. Two methods were explored to incorporate the IL into the polymer matrix: generation of IL onto the surface monolith and copolymerisation by adding IL to the polymerisation mixture, with the latter yielding the best results. The sorbent materials were characterised morphologically and used to isolate five β-blockers from human urine samples. All SPE steps were performed by centrifugation, significantly reducing costs and sample processing time. Under optimal conditions, β-blockers were retained on the modified monolith at pH 12 and desorbed with a water-methanol mixture, followed by HPLC-UV detection. Detection limits ranged from 1.4 to 40 μg/L, and reproducibility (as relative standard deviation) was below 8.2%. The novel phase was successfully applied to propranolol extraction from urine with recoveries above 90%.