Establishment And Application Of LC-MS/MS Method For Five Pesticides In Groundwater

As the largest pesticide-using country in the world,reports of pesticide pollution are increasing in China.Pesticide have a strong impact on environment and human production and living because of the high toxicity.The groundwater quality standard(GB/T 14848-2017)was published in 2017,and we need to develop an analytical method that can cover all pesticide components in the new standard.According to another GC-MS/MS method,the five pesticide components of 2.4-D,2.4.6-trichlorophenol,pentachlorophenol,glyphosate and aldicarb were obtained after screening,because the recovery and the detection limit of the GC-MS/MS method could not meet the test requirements.We chose to use liquid chromatography-tandem mass spectrometry for detection.However,due to the amphiphilicity of glyphosate,the detection of glyphosate typically need derivatization,which may produce unknown interference to the detection of other components.In addition,the pre-processing is complicated and time-consuming.Therefore,it is needed to establish a rapid,sensitive and accurate detection method without derivation.Several common chromatographic columns were tested in the paper,and the mass spectrum and liquid phase parameters were optimized.A simple pretreatment method of large volume injection was established.The detection method was used to detect water samples and additionally the matrix effects of different hydrochemical types were evaluated.The main conclusions of this paper are as follows:(1)AQ column is appropriate to detect the five pesticides due to its enhancing response and high separation performance for polar compounds.Adding ammonium bicarbonate to the aqueous mobile phase could enhance the glyphosate response and reduce peak tailing.(2)50 ?L bulk injection after filtrated was used,and the pH of the sample,adsorption of filter membrane,sample solvent impact and other factors were analyzed to obtain the best pretreatment scheme.The performance verification of the method showed that the detection limits of the five pesticides are 0.093 ~ 1.051 g/L.The detection limits were below the class ? water quality standard stipulated by the GB/T 14848-2017 and could meet the actual needs.(3)The developed method was used to detect the water samples of Yancheng city in Jiangsu province,and Guanling city in Guizhou province.The results show that when the spiked concentration of the different water samples was 5 ?g/L,the recoveries were between 80% and 120% and relative standard deviation(RSD)were less than 10%.(4)The matrix effect of different hydrochemical types was evaluated.The results showed that calcium and magnesium ions would produce ion suppression to the detection of glyphosate,when their concentration were larger than 2 mmol/L.Besides internal standard quantification could compensate for the ion suppression of glyphosate and 2,4-D due to the matrix effect.