Hydroxyl-functionalized covalent organic frameworks as ambient mass spectrometry elements for rapid enrichment, ionization and detection of amide herbicides in astragalus.

A novel, rapid, and sensitive method for the simultaneous detection of seven amide herbicides is proposed. Hydroxyl-functionalized covalent organic frameworks (COF) were selected to be coated on stainless steel substrates (SSS) as enrichment and ionization elements. The prepared COF-SSS extracted analytes based on the principle of solid-phase microextraction (SPME). After COF-SSS extracting the analytes, high voltage electricity was applied and combined with ambient mass spectrometry (AMS) to achieved simultaneous detection within 1.5 min. This COF-SSS-AMS method simplifies the sample pre-treatment procedure, speeds up the detection process and significantly reduces the use of organic reagents. To investigate the reliability of this method, alachlor, metolachlor, acetochlor, pretilachlor, butachlore, napropamide, propachlor were detected. The results demonstrated that the simultaneous detection of the seven amide herbicides in astragalus sample can be realized using the method. The proposed method showed satisfactory linearity in the range 0.05-100 μg/kg with the determination coefficient (R) > 0.9916. The limits of detection (LODs) and limits of quantification (LOQs) were in the ranges 0.03-0.1 μg/kg and 0.1-0.4 μg/kg, respectively, and the relative recoveries were in the range 85.17%-104.09% with the relative standard deviations (RSDs) < 8.32%. In addition, the COF-SSS has superior reusability and batch-to-batch repeatability, which can be re-used at least 7 times and still maintains excellent enrichment performance.