Preparation and characterization of positively charged phenylaminopropyl-bonded core-shell microspheres for separation of polyethylene glycol and diverse compounds.

Core-shell silica microspheres were utilized as the substrate, and phenylaminopropyl groups were covalently grafted to fabricate SiO2@SiO2-PHN. Meanwhile, C18-bonded core-shell microspheres (SiO2@SiO2-C18) were also prepared to compare their separation selectivity. The characterization results revealed that the grafting density of phenylaminopropyl groups was 1.89 μmol/m2. Alkylbenzenes were selected as test analytes to evaluate the fundamental chromatographic performance of SiO2@SiO2-PHN, exhibiting a typical reversed-phase chromatographic retention mechanism, with a column efficiency of 106,800 N·m-1 for toluene. Several kinds of mixed samples were further adopted for comparative chromatographic efficiency. The results showed that SiO2@SiO2-C18 delivered remarkably superior column efficiency for polycyclic aromatic hydrocarbons and terphenyls, and the column efficiencies of pyrene and p-terphenyl reached 215,070 and 231,540 N·m-1, respectively. Nevertheless, SiO2@SiO2-PHN afforded symmetric peak shapes and outstanding resolution for separating pyridine derivatives and quinine and its derivatives. In the separation of two kinds of polyethylene glycol (PEG) derivatives, bisphenol A ethoxylate dimethacrylate (BPA-DMA) and self-synthetic single isocyanate PEG200, baseline separation cannot be achieved on SiO2@SiO2-C18. For BPA-DMA on SiO2@SiO2-PHN, 7 peaks with high response intensities were observed within a retention time of 50-80 min by HPLC-UV. HPLC-MS analysis confirmed that these 7 peaks corresponded to BPA-DMA with gradually decreasing molecular weight from 716 to 452. For separation of single isocyanate PEG200 on SiO2@SiO2-PHN, 8 high-intensity peaks were detected within 15 min by HPLC-UV. As confirmed by HPLC-MS analysis, these 8 peaks could be assigned as PEG with increasing molecular weight from 209 to 517.