The Detection Method Of Glyphosate In The Soil And Sludge

Since the glyphosate?Gly?marketed in 1974,it has become the most widely used and the largest sales of herbicides due to the strong systemicity and a broad spectrum of weed control.Because of the increasing dosage,the extensive using and the moderate retention?t1/2 was 1-174d in the soil?of glyphosate,Gly should be attention in the soil environment pollution.Gly was added as one of the organic pollutants in the draft of "environmental quality standards for soil"?Revised??GB15618-2008?in China.The detection of Gly was difficult due to the chemical properties.The polarity and water solubility of Gly were not conducive to the extraction,and a derivatization step was required before detecting with the chromatographic instrument because the lack of chromophore and fluorophore.Especially in the soil environment,glyphosate was easily adsorbed by soil,by reacting with organic matter,humic acid,metal oxides and heavy metal ions in soil.Therefore,it is more difficult to detect the trace Gly in soil samples.At present,there is no standard test method for glyphosate in soil and sludge.And the previous analytical method reported for Gly,such as analysis with gas chromatography tandem mass spectrometry or liquid chromatography tandem mass spectrometry,could not be widely promoted because of the complex operation and expensive equipment.In order to better monitor and analyze the contamination status of Gly in the soil and sludge,a set of standards should be established which was economical,convenient,accurate and reliable.The standard method for the detection of Gly in the soil and sludge was established in this work.And the effects of physical and chemical properties of soil on the detection of Gly were explored in this paper.Furthermore,According to the requirements of"environmental monitoring--technical guidelines on drawing and revising analytical method standards"?HJ 168?and the "Provisional requirements of the revision work for National environmental pollutant monitoring method standard system"?[2009]10?,the standard method was verified in six laboratories.The main research contents and results were as follows:?1?The establishment of the analysis method for Gly in soil and sludge:the soil/sludge samples were extracted by a mixture solution of 0.03 mol/L sodium phosphate and 0.01 mol/L trisodium citrate aqueous solution.After extracted with ultrasonic,the extracting solution would be adjusted to pH 9 with HCl and decontaminated by hexane.The method was based on derivatization with 9-fluorenylmethylchloroformate?FMOC?followed by High Performance Liquid Chromatography?HPLC?coupled with fluorescence detector analysis.And the mobile phase was a time-programmed using A?acetonitrile?and B?v/v,0.2%phosphoric acid aqueous solution?.The preparation methods were optimized in the work.Due to the similar mechanism of adsorption of Gly and phosphate in the soil,phosphate and Gly compete for adsorption sites,which can reduce the adsorption of Gly and improve the recovery rate.The ion complexing agent was added in order to eliminate the interference caused by metal ions in the soil/sludge.This method is simple and has a good reproducibility.With different concentration ranged from 0.005 mg/L to 0.5 mg/L,the regression equation was regarded as appropriate with a good linear relationship?R2?0.999?.The average recovery rate was 75%-100%,and the relative standard deviation?RSD?was lower than 15%.The limit of detection of the method was 0.01 mg/kg,and the limit of quantitation of the method was 0.04 mg/kg.The recovery and the limit of detection could meet the requirement of"environmental quality standards for soil"?0.5 mg/kg?.?2?The effect of soil physical and chemical properties on Gly was detected by comparing the effects of soil humic acid,soil pH and seven kinds of heavy metal ions on the recovery rate of Gly.The results showed that the higher the content of organic matter in the soil,the stronger the sorption of Gly,which can reduce the recovery rate;the pH value of the soil had a significant impact on the recovery rate of Gly.In acidic soils,Gly was existed in molecular form,while in alkaline conditions,mostly in the form of anion.Meanwhile,soil particles with negative charge,would reduce the adsorption of Gly duo to the repulsive interaction;Heavy metal ions(Cu²⁺,Fe²⁺,Fe3+,Zn²⁺,Ni²⁺)could react with Gly which would Reduce the recovery.However,heavy metal ions of Co²⁺ and Mn²⁺ had no effect on Gly;the detection method of Gly can applied for all kinds of soils/sludge.Because sodium phosphate and trisodium citrate extract has the effect of buffer solution,it can be adapted to a variety of pH environment of the soil,and the trisodium citrate can remove most of the heavy metal ions in the soil.?3?According to the requirements of "environmental monitoring-technical guidelines on drawing and revising analytical method standards"?HJ 168?and the "Provisional requirements of the revision work for National environmental pollutant monitoring method standard system"?[2009]10?,the standard method has been verificated in six qualified laboratories.Six laboratory verification results showed that the method detection limit was 0.011 mg/kg;the lower limit of determination was 0.043 mg/kg which were much lower than the standards limit of environmental quality?0.5 mg/kg?.So it can meet the present and future environmental standards.The repeatability and reproducibility of the method were satisfactory.The reproducibility of the red soil in Hunan was 0.016 mg/kg-0.134 mg/kg,and the reproducibility was 0.034 mg/kg-0.299 mg/kg.The final recovery rate of matrix addition was 99.21%± 11.75%-101.15%± 9.60%;the repeatability limit of paddy soil was 0.015 mg/kg-0.139 mg/kg,and the reproducibility was 0.027 mg/kg-0.214 mg/kg.The final recovery rate of matrix was 83.53%±5.96%-88.79%± 4.11%;the repeatability limit of black soil in Northeast China was 0.016 mg/kg-0.147 mg/kg,and the reproducibility was 0.020 mg/kg-0.172 mg/kg.The final recovery rate of matrix addition was 79.96%± 10.09%-83.66%±3.11%;the repeatability limit of the former lake sludge was 0.017 mg/kg-0.140 mg/kg,and the reproducibility was 0.024 mg/kg-0.178 mg/kg.The final recovery rate of matrix addition was 75.31%±9.70%-80.62%±12.92%;the repeatability limit of the Qinhuai River sludge was 0.018 mg/kg-0.182 mg/kg,and the reproducibility was 0.022 mg/kg-0.208 mg/kg.The final recovery rate of matrix addition was 79.26%%±10.07%82.03%±10.14%.The results showed that the various characteristic indexes of the standard method could meet the expected requirements.