Synthesis and application of a dual-functional fluorescent probe for sequential recognition of Zn²⁺and glyphosate

A novel fluorescent probe QL was designed and synthesized based on Schiff base by 2-hydrazinobenzothiazole to sequentially recognize Zn²⁺ and glyphosate. The probe QL was capable to detect Zn²⁺ in DMSO solution via fluorescence enhancement, and exhibited good selectivity and anti-interference ability. The combination mode was 1:2 between probe QL and Zn²⁺ according to the method of job's plot, and the detection limit of probe QL for Zn²⁺ was found to be 4.51 × 10^-8 M, which exhibited excellent sensitivity. Furthermore, the system QL-Zn²⁺ could detect glyphosate by causing fluorescence quenching response and with a color change from yellow to colorless for naked-eye detection. The detection limit for glyphosate was found to be 4.93 × 10^-8 M, which was far below the Standards for Drinking Water Quality (GB5749-2006) acceptable limits (0.7 μg/mL for glyphosate). Notably, the probe QL and its complex QL-Zn²⁺ have been successfully applied to detect Zn²⁺ and glyphosate in water, respectively.