Multiplexed immunochromatographic strip based on multicolor fluorescent microspheres for simultaneous detection of three herbicides.

A novel multiplex immunochromatographic assay (ICA) based on quantum-dot-encoded multicolor fluorescent microsphere (MFMs) was developed for the simultaneous and quantitative detection of prometryn (PRO), diquat (DQ), and sulfometuron-methyl (SMR). Red, yellow, and green MFMs were fabricated by embedding CdSe/ZnS QDs into polymer microspheres and subsequently conjugated with specific monoclonal antibodies, generating highly uniform MFM-mAb probes with clear and stable emission signals. The multiplex ICA exhibited excellent analytical performance, with limits of detection of 0.41 ng/mL for PRO, 9.36 ng/mL for DQ, and 1.32 ng/mL for SMR, better than most ELISA-based assays. The strip also demonstrated high specificity, good storage stability, and reliable performance in complex matrices. In spiked river water and vegetable samples, recoveries ranged from 85.53% to 109.67% with RSDs of 1.33-7.02%, indicating strong applicability. Overall, this MFM-ICA provides an effective platform for rapid multi-herbicide screening.