Spectroscopic method for the detection of 2,4-dichlorophenoxyacetic acid based on its inhibitory effect towards catalase immobilized on reusable magnetic Fe3O4-chitosan nanocomposite

A spectrometric approach for the sensitive detection of 2,4-dichlorophenoxyacetic acid (2.4-D) was developed based on the inhibitory effect of 2,4-D on the enzymatic activity of catalase. The magnetic Fe3O4-chitosan nanocomposites pre-activated with glutaraldehyde was used as support to improve the stability and reusability of catalase. After determination, the catalase-loaded Fe3O4-chitosan nanocomposites was separated from the reaction mixture using a magnet for repeat use. The activity assay of the immobilized catalase was based on the enzymatic decomposition of H2O2 which was monitored at 290 nm. The activity of the immobilized catalase decreased in the presence of 2,4-D. This inhibition degree was proportional to the concentration of 2,4-D in the range of 0.045-2.5 mu M with a detection limit of 0.02 mu M. Possible inhibition mechanism of catalase by 2,4-D was deduced according to the variation of parameters and a mixed inhibition mechanism was observed. The developed method exhibited good stability, repeatability and reproducibility, which can be used as a promising new tool for the analysis of enzyme inhibitors. (C) 2017 Elsevier B.V. All rights reserved.