COF-300-AR@CRL as a two-in-one nanocatalyst for one-step chemiluminescent detection of diphenyl ether herbicide residues in vegetable and fruit samples.

Abstract

A sensitive and accurate chemiluminescence (CL) method wasdevelopedfor one-step determination of diphenyl ether herbicides at trace level with nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) as a model analyte. Candida rugosa lipase (CRL) was immobilized on a nanocarrier of amine-linked covalent organic framework (named as COF-300-AR) through a self-assembly strategy. The formed nanocomposite of COF-300-AR@CRL owns dual enzymatic catalytic activities. It can directly catalyze luminol-dissolved oxygen reaction to produce an intense CL emission by virtue of oxidase mimic activity of COF-300-AR but also effectively decompose nitrofen to release phenolic compounds by the immobilized CRL. The released phenolic compounds own strong reducing capacity and in turn decrease the CL signal sharply. Under the optimal conditions, the decreased CL intensity presents a good linear response to nitrofen concentration in the 0.02-50.0 μM range. The limit of detection (LOD, 3sb/S) is 11 nM and the precision is 2.0% for replicate measurements of 50.0 nM nitrofen solution (n = 11). This method has the advantages of rapid analytical efficiency, good selectivity, satisfactory stability, and recyclability. Recovery experiments were conducted on spiked vegetable and fruit samples with the recoveries falling in the range 90.0-107.0%.