Abstract
Hypercrosslinked porous organic polymers (HCPs), a novel type of porous materials synthesized via the Friedel-Crafts reaction, are widely used in gas storage, heterogeneous catalysis, chromatographic separation, and organic pollutant capture. HCPs have the advantages of a wide monomer source, low cost, mild synthesis conditions, and easy functionalization. In recent years, HCPs have shown great application potential in solid phase extraction. Given their high specific surface area, excellent adsorption properties, diverse chemical structures, and easy chemical modification, HCPs have been successfully applied to the extraction of different types of analytes with efficient extraction performance. Based on the chemical structure of HCPs, their target analytes, and the adsorption mechanism, HCPs can be classified as hydrophobic, hydrophilic, and ionic species. Hydrophobic HCPs are usually constructed as extended conjugated structures by overcrosslinking aromatic compounds as monomers. Common monomers include ferrocene, triphenylamine, triphenylphosphine, etc. This type of HCPs shows good adsorption effects on nonpolar analytes such as benzuron herbicides and phthalates through strong π-π and hydrophobic interactions. Hydrophilic HCPs are prepared by introducing polar monomers or crosslinking agents, or by modifying polar functional groups. This type of adsorbent is commonly used to extract polar analytes such as nitroimidazole, chlorophenol, tetracycline, etc. In addition to hydrophobic forces, polar interactions, such as hydrogen-bonding and dipole-dipole interactions, also occur between the adsorbent and analyte. Ionic HCPs are mixed-mode solid phase extraction materials formed by introducing ionic functional groups into the polymer. Mixed-mode adsorbents usually have a dual reversed-phase/ion-exchange retention mechanism, which helps control the retention behavior of the adsorbent by adjusting the elution strength of the eluting solvent. In addition, the extraction mode can be switched by controlling the pH of the sample solution and eluting solvent. In this manner, matrix interferences can be removed while the target analytes are enriched. Ionic HCPs present a unique advantage in the extraction of acid-base drugs in water. The combination of new HCP extraction materials with modern analytical techniques, such as chromatography and mass spectrometry, has been widely used in environmental monitoring, food safety, and biochemical analyses. In this review, the characteristics and synthesis methods of HCPs are briefly introduced, and the application progress of different types of HCPs in cartridge-based solid phase extraction is described. Finally, the future outlook of HCP applications is discussed.