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Enhanced Quenching Effect of Neonicotinoid Pesticides on Time-Resolved Terbium Luminescence in Presence of Surfactants
摘要： A luminescence analytical method for the quantification of neonicotinoid pesticides (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam) in water samples is proposed. The method is based on the quenching effect that these analytes produce on the time-resolved luminescence signal of terbium ions (excitation/emission wavelengths of 256/545 nm/nm). An enhancement on the analytical signal is observed when surfactants are used in the system. The use of a 0.01 mol·L?1 sodium dodecyl sulfate produced approximately a 30% increase in the sensitivity of the method. Under the optimum conditions, the method presented detection limits between 0.03 and 0.23 μg·mL?1. Interference studies were performed for ions commonly present in waters, observing no interferences. In addition, recovery experiments were performed in different waters, well, spring, and swamp, observing recovery yields close to 100%, with relative standard deviations lower than 4% in all cases. No sample treatment except a filtration step was required. Hence, this method may represent an alternative to other existing methods for the quick and simple analysis of these ubiquitous insecticides in environmental waters.
关键词： neonicotinoid pesticides,surfactants,time-resolved luminescence,terbium luminescence,water samples
更新于2025-09-04 15:30:14
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Magnesium and nitrogen co-doped carbon dots as fluorescent probes for quenchometric determination of paraoxon using pralidoxime as a linker
摘要： Carbon dots codoped with magnesium and nitrogen (Mg,N-CDs) were synthesized via a one-step microwave-assisted method. They display blue fluorescence (with excitation/emission peaks at 380/460 nm and a 33% quantum yield) and possess high dispersity in aqueous solution. The fluorescence of the Mg,N-CDs is highly sensitive to paraoxon in the presence of pralidoxime (PAM) acting as the linking agent. Electron transfer from Mg,N-CDs to paraoxon in the presence of PAM leads to the fluorescence quenching of Mg,N-CDs. The concentration of paraoxon is determined by measuring the quenching efficiency of the Mg,N-CD-PAM assay system. Fluorescence drops with increasing concentrations of paraoxon in the 0.005–3.0 μM range, and the limit of detection is 0.87 nM. The method is highly selective for paraoxon even in the presence of possible interferences. Real sample study of tap and river water showed the assay to have good repeatability and accuracy.
关键词： Quantum yield,Oxime,Electron transfer,Fluorescence quenching,Organophosphorus pesticides
更新于2025-09-04 15:30:14