Functionalized ionic liquids as an efficient sorbent for solid-phase extraction of tetracyclines in bovine milk

[Display omitted] •Ionic liquid immobilized onto activated silica gel has been prepared for the first time.•The solid-phase extraction of tetracyclines was carefully investigated.•High recovery efficiency and low limit of detection were achieved.•The solid-phase extraction is simple, rapid, and effective in determining the selected tetracyclines. In this research, a novel ionic liquid-based sorbent, N,N,N-trimethyl-3-(triethoxysilyl)propan-1-aminium bromide silica gel (SiO2-NH2), was successfully synthesized through chemical interaction. The synthesized adsorbent was first applied as a stationary phase for the preconcentration of tetracycline antibiotics (TCAs) at trace level from milk samples via solid-phase extraction. The structure of SiO2-NH2 was studied by Fourier-transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Energy-Dispersive X-ray Spectroscopy (EDX), and Scanning Electron Microscopy (SEM) to verify the successful synthesis based on the existence of ionic liquid on the surface of silica gel. The factors impacting a solid-phase extraction procedure were investigated, such as types of material, sample volume, breakthrough volume, and elution conditions. In addition, we also compared self-synthetic SPE cartridges with commercial cartridges with the assistance of LC-MS/MS. The SiO2-NH2 effectively retained and separated all three tetracycline antibiotics, including tetracycline (TC), oxytetracycline (OT), and chlortetracycline (CT), with a recovery efficiency of 99.4 % to 100 %. The maximum recovery was obtained when the analytes were eluted using a suitable mixture of acetonitrile, methanol, and acetic acid (2:2:1, v/v/v) for a volume of 1 mL. The enrichment factors of TC, OT, and CT were 110 mL, 150 mL, and 100 mL, respectively. The detection limits for TC, OT, and CT were 0.360, 0.279, and 0.390 mgL−1, corresponding with lower than 5 % relative standard deviation (RSD).