On-line immobilized acetylcholinesterase microreactor based on capillary electrophoresis for the determination of organophosphorus pesticide residues

In this study, a capillary electrophoresis-based online immobilized acetylcholinesterase (AChE) microreactor was developed for the determination of organophosphorus pesticide (OPs) residues in six fruit and vegetable juice samples. AChE was immobilized on the inner wall at the inlet of the capillary via polydopamine (PDA) coating. The immobilized AChE activity and other kinetic parameters were evaluated by measuring the peak area of the product (thiocholine). The value of Michaelis-Menten constant (Km) was determined to be 3.11 mM, and the half-maximal inhibitory concentration (IC50) and inhibition constant (Ki) of tacrine on immobilized AChE were measured to be 0.46 μM and 0.27 μM, respectively. The activity of the immobilized AChE remained more than 85.0% of its initial immobilized enzyme activity after 30 runs. Then, the developed strategy was successfully applied to detect the acephate in six fruit and vegetable juice samples (apple, pear, peach, tomato, cucumber and lettuce juice) with a limit of detection (LOD) of 11.0 ng/mL. Results show that the recovery of spiked samples are in the range of 86.0-96.0% with RSD of less than 5.7%. Therefore, the proposed method is capable of achieving rapid analysis of acephate with simple operation when there are no other types of OPs in the real samples.