基于共价有机骨架材料的磁固相萃取-超高效液相色谱-串联质谱法测定水中4种杀菌剂

杀菌剂在环境中长期富集后会引起土壤和植物病害,并能借助雨水或灌溉渗透到深层土壤和地下水中,威胁水体环境和人体健康。因此针对水中杀菌剂开发简单快速、高效灵敏的分析方法至关重要。该研究通过原位合成法制备了磁性共价有机骨架材料Fe₃O₄@TpBD,将其作为萃取吸附剂,富集环境水体中苯并咪唑杀菌剂(噻菌灵、麦穗宁、多菌灵)和有机硫杀菌剂(稻瘟灵)。利用Fe₃O₄@TpBD与杀菌剂之间的π-π共轭、氢键和静电作用进行吸附,结合超高效液相色谱-串联质谱法(UHPLC-MS/MS)进行检测,建立了测定水中4种痕量杀菌剂的分析方法。通过透射电子显微镜、X射线衍射及傅里叶变换红外光谱等方式对Fe₃O₄@TpBD进行表征,以证明材料的成功合成。对萃取条件进行一系列的优化(Fe₃O₄@TpBD的磁性比例及用量、水样pH、吸附时间、洗脱液的种类及体积、洗脱时间、NaCl含量),确定了最佳萃取条件。4种杀菌剂在3~1200 ng/L的范围内线性关系良好,线性相关系数均大于0.998,方法的检出限和定量限分别为0.06~0.28 ng/L和0.20~0.92 ng/L。在15、150和600 ng/L 3个加标水平下进行加标回收试验,日内和日间精密度分别为2.8%~10.0%和4.4%~15.7%。将该方法用于实际水样的检测,4种杀菌剂的加标回收率为77.1%~119.1%,在水库水中检测出多菌灵,含量为27.5 ng/L。该方法灵敏度高,准确度和精密度良好,操作简单,耗时短。

Determination of four fungicides in water by magnetic solid phase extraction-ultrahigh performance liquid chromatography-tandem mass spectrometry using covalent organic framework material

Fungicides can lead to soil and plant diseases after long-term enrichment in the environment; they can also penetrate deeper into the soil and groundwater by rainwater or irrigation, threatening the water environment and human health. Therefore, it is crucial to develop a simple, rapid, efficient, and sensitive analytical method for the detection of fungicides in the water environment. Sample pretreatment is important for the extraction and enrichment of pollutants from environmental water. Magnetic solid phase extraction (MSPE) is a new sample pretreatment method, which uses magnetic materials as adsorbents dispersed in solution, and rapid separation can be achieved by the aid of external magnets. Because of its advantages of short analytical time, less organic solvent consumption, and easy separation of adsorbents, MSPE has attracted much attention. The key to MSPE is the preparation of highly selective magnetic adsorbents. Covalent organic frameworks have the advantages of large surface area, good chemical and thermal stability, tunable porous structure, low density, and easy functionalization, all of which are ideal for adsorbing fungicides. The concentration of fungicides in environmental water is low. Ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) has high sensitivity and high selectivity, which is suitable for the analysis of fungicides. In this work, a magnetic covalent organic framework Fe₃O₄@TpBD was prepared by an in situ method, as the MSPE sorbent material to enrich of benzimidazole fungicides (thiabendazole, carbendazim, fuberidazole) and organic sulfur fungicide (isoprothiolane) in environmental water. An extraction method based on π-π conjugation, hydrogen bonding, and electrostatic interaction between Fe₃O₄@TpBD and the fungicides, in combination with UHPLC-MS/MS, was developed for the determination of four trace fungicides in water. Transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Fourier transform-infrared spectroscopy (FT-IR) were performed to confirm the successful synthesis of Fe₃O₄@TpBD and to characterize this material. A series of experiments were carried out to decide the optimal extraction conditions, i. e., the magnetic ratio and dosage of Fe₃O₄@TpBD, pH of the water sample, adsorption time, type and volume of the eluent, elution time, and salinity. Gradient elution was carried out with methanol-water as the mobile phase. The target analytes were separated on an ACQUITY UPLC BEH C18 column (100 mm×2.1 mm, 1.7 μm), and multiple reaction monitoring (MRM) was conducted in the positive electrospray ionization mode. The ion source temperature and ion source voltage were set to 500 ℃ and 5 kV, respectively. The analytical method was established under the optimized extraction conditions. The four fungicides showed good linearity in the range of 3-1200 ng/L, with linear correlation coefficients greater than 0.998. The limits of detection (LODs) and limits of quantification (LOQs) of this developed method were 0.06-0.28 ng/L and 0.20-0.92 ng/L, respectively. Recovery tests were performed at three spiked levels of 15, 150, and 600 ng/L, with relative standard deviations of 2.8% to 10.0% (intra-day) and 4.4% to 15.7% (inter-day). The accuracy of the established analytical method was investigated by using it to test real water samples, and satisfactory recoveries for the four analytes were achieved within 77.1% to 119.1%. Trace amounts of carbendazim were detected in the reservoir water at 27.5 ng/L. The method has good sensitivity, accuracy, and precision, and the operation process is convenient.