Synthesis of C18-modified radial mesoporous core-shell silica microspheres with tunable shell thickness for...

With the advent of ultra-high performance liquid chromatography (UHPLC), core-shell silica microspheres (CSSMs) have emerged to balance system backpressure and column efficiency. As one of the methods for preparing CSSMs, the biphasic synthesis method still faces challenges in precisely controlling the shell thickness. In this study, based on the classical biphasic method, we synthesized CSSMs with a radial mesoporous structure and tunable shell thickness through multi-parameter regulation. Tetrabutylammonium bromide (TBAB) was introduced for the first time as an electrolyte to enhance the ionic strength of the system, effectively promoting the directional deposition of silica oligomers on non-porous silica cores. Through the co-regulation of the amounts of TBAB and tetraethyl orthosilicate (TEOS), as well as the volume ratio of water to n-hexane, CSSMs with tunable shell thickness (59.54-251.93 nm), high specific surface area, and adjustable mesopore size were successfully synthesized. Furthermore, after modifying three CSSMs with different shell thicknesses (synthesized at varying water to n-hexane volume ratios) with octadecyltrichlorosilane (OTS), the resulting C18-modified stationary phases achieved baseline separation of 5 alkylbenzenes, 8 polycyclic aromatic hydrocarbons (PAHs), and 4 phthalate esters (PAEs) within 6 min. The stationary phase also exhibited excellent reproducibility and stability, further demonstrating the practical utility of CSSMs for UHPLC. This method provides a practical and reliable pathway for the rational design of ultra-high performance core-shell stationary phases.