Fluorescent Detection of 2,4-Dichlorophenoxyacetic Acid in Food Samples Based on Covalent Organic Frameworks and MnO 2 N
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Fluorescent Detection of 2,4-Dichlorophenoxyacetic Acid in Food Samples Based on Covalent Organic Frameworks and MnO2 Nanosheets Fei Qu 1,2
&
Yang Sun 1,2 & Shuxian Guo 1,2 & Hang Yan 1,2 & Jinmao You 1,2,3
Received: 27 January 2020 / Accepted: 22 June 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract 2,4-Dichlorophenoxyacetic acid (2,4-D) is a typical chlorinated aromatic herbicide which is widely used because of its low cost. Herein, a new fluorescent assay for 2,4-D is developed based on covalent organic frameworks (COFs) and MnO2 nanosheets. The fluorescence of COFs is quenched effectively by MnO2 nanosheets. Ascorbic acid 2-phosphate (AAP) is hydrolyzed by alkaline phosphatase (ALP) to produce ascorbic acid (AA), which reduces MnO2 nanosheets into Mn2+, so the quenched fluorescence recovers. Additionally, 2,4-D can inhibit the catalytic activity of ALP. Therefore, the addition of 2,4-D quenches the fluorescence of COF-MnO2 system again. Under the optimum conditions, this assay displays a wide linear range of 2,4-D from 1 to 150,000 ng/mL with a limit of detection of 0.36 ng/mL. Then, this method is successfully used to measure 2,4-D in rice, millet, and cucumber samples with satisfactory recoveries. Compared with other probes for 2,4-D detection, both of COFs and MnO2 nanosheets are stable, cost-effective, and easily prepared. The sensitivity and linear range of 2,4-D in this strategy are superior to most reported works. This is the first time that a novel sensing platform using fluorescent COFs and MnO2 nanosheets is developed for 2,4-D. Keywords Covalent organic frameworks . MnO2 nanosheets . Alkaline phosphatase . Food . 2,4-Dichlorophenoxyacetic acid
Introduction Nowadays, pesticides are important substances for controlling crop growth and pests (Pang et al. 2016; Lin et al. 2004). 2,4-D is a typical phenoxy acid herbicide (structure in Fig. S1) and is used to control broad-leaf weeds (Park et al. 2011). As one of the top 10 pesticides, 2,4-D is widely used because of its low cost Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12161-020-01807-2) contains supplementary material, which is available to authorized users. * Fei Qu [email protected] 1
The Key Laboratory of Life-Organic Analysis, Qufu Normal University, Qufu 273165, Shandong, China
2
The Key Laboratory of Pharmaceutical Intermediates and Analysis of Natural Medicine, Qufu Normal University, Qufu 273165, Shandong, China
3
The Key Laboratory of Tibetan Medicine Research & Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Chinese Academy of Science, Xining 810001, China
(Wang et al. 2016). However, the improper treatment and abuse usually produce 2,4-D residues in crops (Park et al. 2011). Humans can be indirectly exposed to 2,4-D due to 2,4-D accumulation in the food chain. Moreover, 2,4-D can be absorbed through the skin and gastrointestinal tract and further disrupts endocrine activities (Wang et al. 20
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