Hypercrosslinked core-shell polymer microspheres with amphipathic and amphoteric character for the solid-phase...

Solid-phase extraction (SPE) is used extensively in analytical chemistry for the preconcentration and fractionation of analytes prior to chemical analysis, with enhancements in sorbent efficiency and selectivity being important R&D topics. Although core-shell particles are increasingly used as alternatives to traditional high-performance liquid chromatography (HPLC) stationary phases, their value as SPE sorbents is under-explored. Herein, we describe the design, synthesis and exploitation of core-shell polymer microspheres, where the microspheres are small (3.7 µm) and uniform (C_v = 5.5%), and where the shells are thin (~0.5 µm, which improves mass transfer and reduces eddy diffusion) and have high specific surface area (>1300 m²/g) and amphoteric character. The latter feature means that these microspheres offer both anion-exchange and cation-exchange interactions, which makes the SPE of anions and cations possible. Following synthesis, an SPE protocol using these microspheres as sorbent was optimized and validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous retention of acidic and basic pharmaceuticals present in complex water samples. The inclusion of a clean-up step reduced matrix interferences. The method developed achieved satisfactory apparent recoveries (23-75% for river water, 20-88% for effluent wastewater, and 19-56% for influent wastewater), low matrix effects, detection limits within 0.05-2 ng/L for most compounds, and good repeatability and reproducibility across all sample matrices. Application of the SPE method to real environmental samples confirmed the presence of several target pharmaceuticals at ng/L concentration levels, demonstrating the applicability of the hypercrosslinked core-shell sorbent.