关键词: 磁固相萃取, 咔唑, 超交联聚合物, 四环素类抗生素, 环境水样

Abstract:

This study prepared a novel magnetic carbazole-based hypercrosslinked polymer （Fe₃O₄/car-HCP）. Electron-rich and rigid carbazole served as the functional monomer. Formaldehyde dimethyl acetal （FDA） was used as the crosslinker. Ferric chloride （FeCl₃） acted as both catalyst and iron source. Systematic characterization revealed the material’s chemical structure，morphology，pore properties，and magnetic behaviour. Specifically，the material exhibited a high specific surface area and a well-developed porous network. It also showed superparamagnetic properties with sufficient saturation magnetization for rapid magnetic separation. The material offers several advantageous features for analytical extraction. Its carbazole aromatic skeleton provides strong π-π stacking interactions with the aromatic rings of tetracycline antibiotics （TCs）. The same skeleton also supplies hydrogen bonding sites，primarily through its nitrogen atom. Both types of interactions exhibit high affinity toward TCs. The hypercrosslinked network confers high hydrophobicity to the material. This property effectively minimizes non-specific adsorption of polar matrix components commonly present in environmental water samples，such as humic acid and inorganic salts. The embedded Fe₃O₄ nanoparticles enable rapid magnetic responsiveness. This allows convenient and fast separation of the adsorbent from the sample solution using an external magnet，eliminating the need for centrifugation or filtration steps. These structural and physicochemical features work together in a synergistic manner. Consequently，the material achieves multi-mechanistic adsorption of the target analytes，leading to high extraction efficiency. Using this material as a magnetic solid-phase extraction （MSPE） adsorbent，an analytical method was developed. The MSPE procedure was coupled with high performance liquid chromatography-ultraviolet detection （HPLC-UV）. The method allows for the simultaneous determination of three TCs in environmental water samples. The three TCs are oxytetracycline （OTC），tetracycline （TC），and doxycycline （DC）. Several extraction parameters were systematically optimized to achieve the best performance. The parameters included adsorbent dosage，extraction time，extraction temperature，eluent composition，elution time，and elution volume. The optimal extraction conditions were as follows： The sample was extracted with 20 mg of adsorbent at 30 ℃ for 30 min，and then eluted with 3 mL of acetonitrile/0.01 mol/L NaOH （2∶1，volume ratio） for 20 min. Under these optimized conditions，the method demonstrated satisfactory analytical performance. The linear range was 2.83–200 μg/L for OTC，2.77–200 μg/L for TC，and 9.93–200 μg/L for DC. The limits of detection （LODs），based on signal-to-noise ratio （S/N）=3，ranged from 0.83 μg/L to 2.98 μg/L. The limits of quantification （LOQs，S/N=10） ranged from 2.77 μg/L to 9.93 μg/L. The method was then applied to the analysis of real water samples. Three types of water were tested： tap water，rainwater，and landscape lake water. Recovery tests were conducted at two spiked concentration levels，namely 10 μg/L and 100 μg/L. The average recoveries of the three target analytes ranged from 75.6% to 128.5%. The relative standard deviations，calculated from three replicate measurements，were between 1.3% and 9.4%. These results confirm that the method is accurate，reliable，and applicable to complex aqueous matrices. Compared with previously reported methods for TC analysis，the present approach offers several distinct advantages. It requires significantly less adsorbent. It also simplifies the operational procedure by eliminating time-consuming steps. Importantly，these improvements are achieved without sacrificing sensitivity or accuracy. In summary，this study provides a robust，convenient，and efficient analytical solution for monitoring trace levels of TCs in environmental water. Furthermore，the design and synthesis strategy of this multifunctional magnetic adsorbent offers new insights for developing advanced functional materials for environmental sample preparation.

Key words: magnetic solid-phase extraction （MSPE）, carbazole, hypercrosslinked polymer, tetracycline antibiotics, environmental water samples