An octadecyl (C18) sorbent via cyanuric chloride condensation for the QuEChERS-HPLC-FLD analysis of four fluoroquinolones in cosmetic samples.

Prolonged use of cosmetics containing banned fluoroquinolones can cause skin disorders and increase drug resistance. The QuEChERS method holds considerable application prospect in the pretreatment of cosmetic samples. Although octadecyl (C18)-bonded silica sorbent is commonly used as a QuEChERS clean-up material, the conventionally commercially available bulk C18 sorbent is relatively costly and has a limited purification mechanism. In this study, using dendritic silica sphere (dSiO2) as the substrate, and through the condensation reaction between cyanuric chloride (CNCl) and the amino group, a dNSiO2-CNCl-C18 sorbent was synthesized. The sorbent was characterized using infrared spectroscopy, transmission electron microscopy, surface area and pore size analysis, and water contact angle measurements. The experimental results regarding the matrix removal from the model cosmetic lotion showed that dNSiO2-CNCl-C18 exhibited a higher matrix removal efficiency compared to a commercial C18 sorbent. Furthermore, a QuEChERS-HPLC-FLD method was developed using dNSiO2-CNCl-C18 for the simultaneous detection of four fluoroquinolones, norfloxacin (NOR), pefloxacin (PEF), enrofloxacin (ENR), and difloxacin (DIF). The linear ranges were 0.10 to 100.0 μg L-1 for NOR and PEF, and 0.05 to 100.0 μg L-1 for ENR and DIF, with coefficient of determination exceeding 0.999. Satisfactory spiked recoveries for the lotion sample ranged from 91.5% to 107.0%, with intra-day and inter-day precision values not exceeding 7.6%. The established method was subsequently validated through its successful application in additional cream and emulsion samples. dNSiO2-CNCl-C18 exhibits low synthesis costs and demonstrates promising potential for matrix purification in various complex samples, facilitating the rapid determination of target compounds.