A Low Matrix Effects Analytical Strategy for Diazepam Analysis in Aquatic Products Through Immunomagnetic Beads Purification

A low matrix effects (MEs) analytical strategy was developed for quantifying diazepam (DZP) in aquatic products by combining immunomagnetic bead (IMB)-based sample pretreatment with UPLC-MS/MS. The preparation conditions of IMBs, sample extraction, and purification were systematically optimized. Due to the weak MEs of this method, the quantification of DZP was carried out using a solvent-based calibration curve with an external standard solution. Good linearity was achieved over the range of 0.5–20 ng/mL with a correlation coefficient (R2) of 0.9971. The LOD and LOQ were 0.125 μg/kg and 0.25 μg/kg, respectively. Recoveries ranged from 85.5% to 106%, with intra-day and inter-day precisions of 1.16–7.04% and 3.42–8.99%, respectively. This work has established a robust, rapid, and practical methodology for DZP residue monitoring in aquatic products. Moreover, it serves as a methodological foundation for the detection of other low-molecular-weight contaminants in complex food matrices, thereby enhancing the surveillance and risk assessment for aquaculture products.