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

A glycidyl methacrylate-based monolith was modified with imidazolium-based ionic liquid (IL) to be used as stationary phase for solid-phase extraction (SPE). The host monolithic support was prepared by in-situ UV polymerization in spin column format. Two approaches were developed to incorporate the IL into the polymeric monolithic matrix: generation of IL onto the surface monolith, and copolymerization by addition of the IL to the polymerization mixture, which gave the best results. The resulting sorbent materials were morphologically characterized and used for the isolation of five β-blockers from human urine samples. All SPE steps were accomplished by centrifugation, which reduces significantly costs and time in sample treatment. Under optimal conditions, β-blockers were quantitatively retained in the modified monolith at pH 12, and desorbed with a water-methanol mixture, to be subsequently determined via HPLC with UV detection. The limits of detection ranged between 1.4 and 40 μg L^-1, and the reproducibility among extraction units (expressed as relative standard deviation) was below 8.2%. The novel phase was successfully applied to the extraction of propranolol in urine samples with recoveries above 90%.