Novel water-compatible surface molecularly imprinted polymer microspheres based on boronate affinity and hydrophilic coating for efficient enrichment and separation of capecitabine from urine samples

A novel water-compatible surface molecularly imprinted polymer microspheres (SMIMs) based on boronate affinity and hydrophilic coating were developed for the specific recognition and extraction of capecitabine (CAP). The boronic acid-functionalized polymer microspheres (BPMs) were first prepared as the carrier through dispersion polymerization using methyl methacrylate, ethylene glycol dimethacrylate, and 4-vinylphenylboronic acid as the polymerization monomers. Subsequently, the CAP template was immobilized onto the surface of the BPMs by virtue of boronate affinity. Finally, a thin and adherent imprinting layer was coated onto the surface of the BPMs via in-water self-polymerization of dopamine (DA) and polyethyleneimine (PEI). The resulting SMIMs exhibited strong hydrophilicity, high adsorption capacity (151.52 μmol/g) and a great imprinting factor (5.99) for CAP in aqueous media. The adsorption behavior of CAP onto the SMIMs was in good agreement with the Langmuir model and the pseudo-second-order equation. Selective adsorption indicated that the SMIMs exhibited a higher specific recognition for CAP compared to other structural analogs. In addition, the SMIMs showed excellent reproducibility and reusability, and could be utilized as an   adsorbent in solid-phase extraction (SPE) for the selective pre-concentration, purification, and detection of trace amounts of CAP in spiked urine samples in combination with HPLC. The elution recovery of CAP for the various spiked levels ranged from 91.7 % to 104.9 %, with a relative standard deviation (RSD) of less than 5.8 % (n = 3).