Construction And Application Of Fluorescence Sensing System For The Detection Of Glyphosate

Glyphosate is an organophosphorus herbicide with a strong intake transportation function and a broad-spectrum effect,which has become the most widely used herbicide species with the largest production and sales volume.The long-term,widespread use of glyphosate has led to a large number of residues in crops,soil,water,and other places.Especially in glyphosate-resistant transgenic crops,the residual amount of glyphosate is hundreds of times higher than that in ordinary crops.Due to the reproductive toxicity,mutagenicity,and other environmental hormone effects of glyphosate,it is extremely harmful to human health and the ecological environment.Therefore,the level of glyphosate residues has become the focus of monitoring in food,the environment,and other related fields.Glyphosate is a strongly polar amphiphilic compound with poor volatility and no color-emitting or fluorescent groups,which makes its quantitative detection difficult.Although chromatographic methods and chromatographic-mass spectrometric methods have met the needs of glyphosate detection to a certain extent,there are still some problems such as cumbersome detection operations,time consuming,high cost,and difficulty in achiev ing high throughput detection,especially for rapid identification and visualization of glyphosate.Aiming at the above problems,a substituted salicylhydrazone fluorescence sensing system was designed to realize the fluorescence detection of glyphosate.The fluorescence sensing system of diethylamino electron donor coumarin acylhydrazone was constructed,which improved the response speed and sensitivity of glyphosate detection.Alkyne-bridged electron donor coumarin acylhydrazone fluorescence sensing system and quinoline acylhydrazone fluorescence sensing system were constructed to improve the visual detection performance of glyphosate.The structures of the intermediates and probes were characterized by ¹H NMR,¹³C NMR,IR,HRMS,etc.,and the mechanism of the fluorescence sensing system for detecting glyphosate was investigated.The performances of the fluorescence sensing system for detecting glyphosate were examined,and the relationship between the structure and performance of the fluorescence sensing system was explored.The main research contents and results are as follows.（1）Probes 3a～3d were prepared by introducing heterocyclic groups through aldehyde-amine condensation reactions with substituted salicylhydrazone derivatives as substrates.The results showed that probe 3d exhibited a specific fluorescence quenching response with Cu²⁺and formed a 1:1 complex.The complex(3d-Cu²⁺)showed a significant fluorescence enhancement response with glyphosate at 525 nm,and the linear range was 0.28～11.00μmol/L,the detection limit was 47.51 ng/m L,the response time was 30 s,and the p H range was 3～8.The spiked recoveries of glyphosate in the actual samples ranged from 92.16%to103.68%with the relative standard deviations of 0.36～4.19%.（2）Based on 7-diethylaminocoumarin-3-acylhydrazone with a diethylamino electron donor at the C7 position of the coumarin core,probes 4a～4c were prepared by introducing heterocyclic groups through aldehyde-amine condensation reactions.The results showed that probe 4b exhibited a specific fluorescence quenching response with Cu²⁺and formed a 2:1 complex.The complex(4b-Cu²⁺)showed a significant fluorescence enhancement response with glyphosate at 493 nm,and the linear range was 0.06～5.00μmol/L,the detection limit was 10.95 ng/m L,and the response time was 8 s.The spiked recoveries of glyphosate in the actual samples ranged from 92.89%to 122.80%with the relative standard deviations of 0.25～3.38%.（3）Based on 7-（4-methoxyphenylethynyl）-coumarin-3-acylhydrazone with an alkyne electron donor at the C7 position of the coumarin core,probes 5a～5c with a“D-π-A”chain conjugated structure were prepared by introducing heterocyclic groups through aldehyde amine condensation reactions.The results showed that the fluorescence emission wavelength of the probe could be red shifted by appropriately increasing the length of the conjugated system and enhancing the intramolecular charge-transfer transition.The probe 5c exhibited a specific fluorescence quenching response with Cu²⁺and formed a 1:2 complex.The complex(5c-Cu²⁺)showed a significant fluorescence enhancement response with glyphosate at 550 nm,and the linear range was 0.07～16.00μmol/L,the detection limit was 11.32 ng/m L,the response time was 5 s,and the p H range was5～9.The spiked recoveries of glyphosate in the actual samples ranged from91.68%to 103.62%with the relative standard deviations of 0.96～3.35%,and the visual qualitative detection of glyphosate was realized.（4）Probes 6a～6d were prepared by introducing heterocyclic groups through aldehyde-amine condensation reactions with quinoline acylhydrazone derivatives as substrates.The results showed that probe 6d exhibited a specific fluorescence quenching response with Cu²⁺and formed a 1:1 complex.The complex(6d-Cu²⁺)showed a significant fluorescence enhancement response with glyphosate at 530nm,and the linear range was 2.00～12.00μmol/L,the detection limit was 9.48ng/m L,the response time was 5 s,and the p H range was 4～10.The spiked recoveries of glyphosate in the actual samples ranged from 9 0.67%to 123.23%with the relative standard deviations of 0.16～6.37%.Moreover,the complex6d-Cu²⁺had excellent visual recognition effects,which could be prepared into a glyphosate colorimetric tube kit.The experimental results show that the fluorescence sensing system constructed by acylhydrazone probes and Cu²⁺complexes achieve rapid,high-sensitivity,and visual detection of glyphosate specificity through ligand replacement reactions,which provides a new idea for the detection of glyphosate residues.