Preparation of a mixed-mode silica-based sorbent by click reaction and its application in the determination of primary aromatic amines in environmental water samples

Abstract

A mixed-mode silica-based sorbent (silica-WCX) with a weak cation-exchange character was prepared via Cu (I)-catalyzed azide–alkyne cycloaddition (CuAAC) click reaction. Firstly, silica particles reacted with 3-azidopropyltriethoxysilane to produce the azide-modified silica (azide–silica). After that, the azide–silica reacted in sequence with 5-hexynoic acid and 1-dodecyne via CuAAC reaction to prepare the silica-WCX sorbent bearing both carboxyl and n-dodecyl groups. The resultant silica-WCX sorbent was characterized by Fourier transform-infrared spectroscopy and element analysis, which proved the successful immobilization of 5-hexynoic acid and 1-dodecyne on the silica surface. Then, the silica-WCX sorbent was used as a SPE sorbent for the determination of primary aromatic amines (PAAs) in water samples by high performance liquid chromatography. Several parameters affecting the extraction efficiency were optimized. Under the optimized SPE conditions, the linear ranges of the proposed method varied from 1 μg L⁻¹ to 800 μg L⁻¹ with correlation coefficients (R²) above 0.998 for all the analytes. The limits of detection (S/N = 3) ranged from 0.08 μg L⁻¹ to 0.28 μg L⁻¹. The intra-day and inter-day precision ranged from 2.7 to 7.8% and from 4.6 to 8.5%, respectively. Finally, the method was applied to the determination of the PAAs in real water samples, including tap water, lake water and printing and dyeing wastewater. The recoveries of PAAs were between 85% and 111% with relative standard deviations (RSDs) less than 7.9%, except that of 4,4′-methylenedi-o-toluidine in printing and dyeing wastewater samples.