Extraction performance of SiO₂@COF before and after carbonization and online SPE-HPLC-DAD methods for...

The property of organic materials can be regulated by a facile carbonization way. In-situ growth of covalent organic framework on silica (SiO₂@COF) was achieved by room temperature synthesis, then SiO₂@COF was carbonized to get another material, called SiO₂@C-COF. The materials were characterized by SEM, BET, XPS, contact angle test and element analysis. Their extraction mechanisms were evaluated by different model analytes. According to thermodynamic functions, SiO₂@COF mainly provided π-stacking effect, while SiO₂@C-COF had stronger hydrophobic interaction. Results of dynamic adsorption capacity further verified it, SiO₂@COF captured more polycyclic aromatic hydrocarbons (273.62 μg g^-1) than SiO₂@C-COF (216.89 μg g^-1), but it had lower adsorption capacity (44.40 μg g^-1) for hydrophobic alkylbenzenes than that on SiO₂@C-COF (56.22 μg g^-1). So, the carbonization was proved as one effective approach to regulate the surface property of COFs and expand the application fields. Based on these, tetrabrombisphenol A derivatives and phthalates were selected as the analytes. After investigating extraction and desorption conditions, two online solid-phase extraction-liquid chromatographic methods were separately established to detect two types of analytes in water samples. Both methods displayed low detection limits (0.005 μg L^-1; 0.01 μg L^-1), wide linear ranges (0.0165-15.0 μg L^-1; 0.033-15.0 μg L^-1), acceptable recoveries (75.55 %-127.78 %; 71.01 %-134.80 %), and satisfactory precision (RSDs, 0.1 %-7.9 %; 0.8%-7.9 %), respectively. Compared with other methods, these methods presented some superiorities like better sensitivity, online analysis, and better repeatability. In addition, the sorbents were durable more than 100 runs.