Research On The Quantification Of Glyphosate Residue In Agricultural Irrigation Water By Fluorescence Analysis

Glyphosate [glyphosate, N-phosphonomethyl glycine (PMG)] is a kind of non-selective and sterilant herbicides, which is widely used in agricultural production. Although PMG has long time been considered as a kind of low toxicity and safety of herbicides, but with the increase of the dosage, the PMG concentration in the water become higher and higher. Human health is threatened by it, finding out the methods that can rapidly and accurately measure its residue is become an urgent demand. As herbicides PMG concentration in soil water is very low, so enrichment needs for its analysis. This study developed europium (Ⅲ)-tetracycline-PMG (Eu(Ⅲ)-TC-PMG) fluorescence enhancement method for selective determination of PMG combined with ionic liquid extraction enrichment and microchip electrophoresis separation-laser induced fluorescence analysis method.(1) The ionic liquid extraction research of PMG Ionic liquid is a molten salt at room temperature or near room temperature liquid, entirely composed of cationic organic ions and anionic inorganic ions. Since it has unique physical and chemical properties (such as low vapour pressure, good thermal stability, non volatile, low melting point, good transmittance to light, unique solvability and designability, etc.) suitable as a green solvent for separation and purification. The content PMG in agricultural irrigation water is low, so in this study ionic liquid had been chosen for sample enrichment. A survey of different acidity, ionic strength, the surfactant concentration and extraction time on the PMG extraction efficiency. Under the optimum extraction conditions (pH 2.2,0.2 mol/L NaCl,100 mol/L Tx-100), the enrichment ratio is of 12.2 times.(2) Eu(Ⅲ)-TC fluorescence enhancement method for PMG analysis in agricultural irrigation water. Lanthanide itself presents a weak fluorescence under UV irradiation, but after TC complexation the EuTC complex emits strong fluorescence. The reason is that the TC molecules acts as an antenna absorbs light energy and transfer it to a corresponding energy level of Eu3+ and enhances the Eu3+ fluorescence. In this study, PMG used as auxiliary complexing agent complex with Eu-TC to form ternary complex Eu-TC-PMG, rendering the enhanced fluorescence. By fluorescence and spectrophotometer analysis, Eu-TC-PMG ternary complex emits at λem= 616 mm (λex= 403 nm), a quantitative relationship is established with the ΔF of the difference between Eu-TC-PMG and the Eu-TC background value. Standard curve was made by the implementation of agricultural irrigation water remaining PMG quantitative analysis. In 5.0×10-4 mol/L Eu3+, 1.0×10-4 mol/L TC pH 10.0,0.01 mol/L tris buffer solution, standard curve linear range for 5.0×10-8-1.5 ×10-4 mol/L, the linear correlation coefficient R of 0.9997. The detection limit of 1.0 × 10-8 mol/L. Recovery is 95.31%～95.31%.(3) Microchip electrophoresis (microchip CE) with laser induced fluorescence analysis of the content of residual PMG in agricultural irrigation water. The previous Eu-TC-PMG analysis method is cannot be used in the presence of a high concentration of heavy metal ions and the amino acid owing to serious interference. In order to thoroughly get rid of such interference and to obtain high sensitivity detection, realize fast and exact determination, this study focus on the microchip electrophoresis with laser induced fluorescence analysis. For the experiment microchip electrophoresis setup is self-maded. To realize fluorescence detection for PMG and its metablites, all samples including amino acids which might exist in real sample are derivatized using Fluorescein isocyanate (FITC), and then the samples applied to microchip CE system analyzing the residual PMG concentration in agricultural irrigation water. Chip demension and materials used is 50 μmx50 μmx4cm of polydimethylsilane (PDMS). To get stable EOF of channel surface the channel inner surface is coated with polyvinylsilazane (PVSZ), and it characterized with infrared spectroscopy, contact angle and XPS both on the surface of original coating and after hydrolysis. PMG standard curve linear over the range of 5.0×10-7-1.0×10-4 mol/L, linear correlation coefficient R is 0.9996. Detection limit of 1.O×10-7 mol/L is obtained. Average recovery is 102.8% and 105.9% for 10-4 mol/L and 10-5 mol/L, respectivily.