Development of a Sensitive and Fast Determination Method for Trace Carbaryl Residues in Food Samples Based on Magnetic COF (TpPa-NH₂)@Fe₃O₄ Nanoparticles and Fluorescence Detection

Developing a simple and effective method for measuring carbaryl residues in food is urgent due to its widespread use and the associated health risks in agriculture, as well as various defects in existing detection techniques. The COF (TpPa-NH₂)@Fe₃O₄ nanocomposite (amino modification) was synthesized via a two-step method and used as an adsorbent for the extraction of carbaryl from food samples in this study. The results indicated that COF (TpPa-NH₂)@Fe₃O₄ can rapidly and successfully capture carbaryl directly from samples via π-π stacking and hydrophobic interactions, achieving maximum adsorption within 5 min under a small adsorbent quantity using a fluorescence spectrophotometer. Under the optimized conditions, carbaryl exhibited good linearity in the range of 0.2-120 µg·kg^-1, and the limit of detection was 0.012 µg·kg^-1. The recoveries of the samples were 96.0-107.4%. This method has broad application prospects for the monitoring of carbaryl in food.