NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, University Hall, Tan Chin Tuan Wing #04-02, 21 Lower Kent Ridge Road, Singapore, 119077, Singapore.
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
Mikrochim Acta. 2021 Jan 7;188(2):30. doi: 10.1007/s00604-020-04661-5.
A novel solvent-loaded dispersive solid-phase extraction (SL-DSPE) method integrated with liquid-phase microextraction (LPME) has been developed by the direct loading of solvent into the pores of a metal-organic framework (MOF), MIL-101(Cr)-NH. Despite numerous advantages of MOFs, they are usually highly hydrophobic which limits their dispersibility and therefore effective contact with the analytes in aqueous samples. To overcome this and promote its interactions with polar compounds, MIL-101(Cr) was functionalized with -NH and loaded with a comparatively polar organic solvent, dichloromethane. The purpose of dichloromethane was to condition the MIL-101(Cr)-NH, promote LPME of the analytes and facilitate the re-collection of the materials after the extraction. Five chlorophenoxy acid herbicides, including 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid, and 2-(2,4,5-trichlorophenoxy)propionic acid, were studied and determined by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). MIL-101(Cr)-NH was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and surface area measurement. Several extraction parameters were optimized, and under the most favorable conditions, the SL-DSPE-UHPLC-MS/MS method achieved enrichment factors between 25 and 66. Low limits of detection (2.66-19.7 ng·L) and wide dynamic working ranges with good linearity (r ≥ 0.991) were attained for all analytes. The method was repeatable, with intra- and inter-day relative standard deviations (RSDs) below 4.5 and 7.6%, respectively, for three replicate determinations. The application of SL-DSPE-UHPLC-MS/MS to paddy field waters gave satisfactory relative recoveries ranging between 80.2 and 108%, with RSDs better 8.4%. Several of the CPAs were detected in these samples. Graphical abstract Schematic of the solvent-loaded dispersive solid-phase extraction procedure. By directly loading dichloromethane into the pores of MIL-101(Cr)-NH, this method improves the extraction capability of the sorbent through the combination of solvent- and sorbent-based microextraction.
一种新型溶剂负载分散固相萃取（SL-DSPE）方法与液相微萃取（LPME）相结合，通过将溶剂直接载入金属有机骨架（MOF）MIL-101（Cr）-NH 的孔隙中而开发。尽管 MOFs 具有许多优点，但它们通常具有很强的疏水性，这限制了它们的分散性，从而限制了它们与水溶液中分析物的有效接触。为了克服这一问题并促进其与极性化合物的相互作用，MIL-101（Cr）用-NH 官能化，并负载相对极性有机溶剂二氯甲烷。二氯甲烷的目的是调节 MIL-101（Cr）-NH，促进分析物的 LPME，并在萃取后方便材料的再收集。五种氯苯氧基酸除草剂，包括 2,4-二氯苯氧乙酸、2,4,5-三氯苯氧乙酸、4-氯苯氧乙酸、2-（2,4-二氯苯氧）丙酸和 2-（2,4,5-三氯苯氧）丙酸，通过超高效液相色谱-串联质谱法（UHPLC-MS/MS）进行了研究和测定。MIL-101（Cr）-NH 采用 X 射线衍射、傅里叶变换红外光谱、扫描电子显微镜和表面积测量进行了表征。优化了几个萃取参数，在最有利的条件下，SL-DSPE-UHPLC-MS/MS 方法实现了 25 至 66 的富集因子。所有分析物均具有低检测限（2.66-19.7ng·L）和宽动态工作范围，线性良好（r≥0.991）。该方法重复性好，三个重复测定的日内和日间相对标准偏差（RSD）分别低于 4.5%和 7.6%。SL-DSPE-UHPLC-MS/MS 法用于稻田水，相对回收率在 80.2%至 108%之间，RSD 优于 8.4%。在这些样品中检测到了几种 CPAs。示意图溶剂负载分散固相萃取程序示意图。通过将二氯甲烷直接载入 MIL-101（Cr）-NH 的孔隙中，该方法通过溶剂和固相亲和微萃取的结合，提高了吸附剂的萃取能力。
