Molecularly imprinted phloroglucinol–formaldehyde–melamine resin prepared in a deep eutectic solvent for selective recognition of clorprenaline and bambuterol in urine

Abstract

A new molecularly imprinted phloroglucinol–formaldehyde–melamine resin (MIPFMR) was synthesized in a deep eutectic solvent (DES) using phenylephrine as a dummy template. The MIPFMR was used as a solid phase extraction (SPE) sorbent for the selective isolation and recognition of clorprenaline (CLP) and bambuterol (BAM) in urine. Phloroglucinol and melamine were used as double functional monomers that introduced abundant hydrophilic groups (such as hydroxyl groups, imino groups, and ether linkages) into the MIPFMR, making it compatible with aqueous solvents. In addition, the formation of DES by combining the quaternary ammonium salt of choline chloride with ethylene glycol as a hydrogen bond donor was an environmentally safe alternative to toxic organic solvents such as chloroform and dimethylsulfoxide that are typically used in the preparation of most molecularly imprinted polymers (MIPs). Moreover, MIPFMR-based SPE of CLP and BAM in urine resulted in higher recoveries and purer extracts than those obtained by using other SPE materials (e.g., SCX, C18, HLB, and non-imprinted phloroglucinol–formaldehyde–melamine resin (NIPFMR)). The optimized MIPFMR–SPE–HPLC–UV method had good linearity (r2 ≥ 0.9996) ranging from 15.0 to 3000.0 ng mL−1 for CLP and BAM, and the recoveries at three spiked levels ranged from 91.7% to 100.1% with RSDs ≤7.6%. The novel MIPFMR–SPE–HPLC–UV method is simple, selective, and accurate, and can be used for the determination of CLP and BAM in urine samples.