Functionalized Fluorescein for Rapid and Colorimetric Assay of Pirimicarb via Halogen and Hydrogen Bonding Synergistic Effect

Pirimicarb is a carbamate insecticide, widely used due to its specific control effect on aphid populations. However, the European Food Safety Authority conducted a risk assessment and proposed regulatory endpoints for it in October 2024. Therefore, there is an urgent need to develop rapid, sensitive, and convenient rapid detection technologies for pirimicarb. Thus, this study proposes an enzyme-free rapid detection method: using 4,5,6,7-tetrabromo-2′,4′,5′,7′-tetraiodofluorescein (RB2) as a detection probe, since the synergistic effect of halogen and hydrogen bonding between RB2 and pirimicarb (PIB) in acidic aqueous solution induces charge transfer and leads to a distinct color change in RB2, thereby enabling the rapid detection of PIB. This method has good selectivity, and a limit of detection (LOD) of 0.0321 mg·L−1 in aqueous solution is achieved with a visual detection time of less than 60 s for PIB. And the LODs for PIB in cucumber and tomato peel samples are 0.0536 mg·L−1 and 0.0243 mg·L−1, respectively. Importantly, this method does not require enzymes as a vehicle in the detection process; it solely relies on the synergistic effect of halogen and hydrogen bonding between RB2 and PIB to achieve visual identification and detection of PIB, providing a reference method for the rapid detection of PIB.