Elimination Of A Surfactant Interference In UPLC-MS/MS Detection Of Pesticides In Water By Selective Solid Phase Extraction Sample Pretreatment

Pesticides have been widely used in agriculture and a considerable part of them are refractory and toxic organic pollutants.With the surface runoff and subsurface flow so that the natural water body is contaminated by pesticides.The detection of toxic pesticide compounds has become an important research topic in water quality management.At the same time,due to the wide range of surfactants in the chemical and life areas of production and use,these compounds will be different ways into the natural water and cause a certain degree of pollution.When the surfactant contains a surfactant,it may have a negative effect on the detection of pesticides,even if the concentration is low,particularly in relation to liquid chromatography separation.And these effects have not been reported in the current research literature.This study is the use of ultra-high performance liquid chromatography–electrospray ionization mode-triple quadrupole mass spectrometry?UPLC-ESI-MS/MS?to develop pesticides detection methods.At the same time,the presence of surfactant sodium dodecyl sulfate?SDS?in the solution will have an effect on chromatographic separation and inhibition of pesticides detection signal.In order to eliminate the influence of SDS,a selective solid phase extraction method was proposed.Through the systematic study,this selective solid phase extraction method can adsorb and remove the surfactant SDS from the pesticide solution while retaining the pesticide in the solution to eliminate the effect of the SDS matrix effect on the pesticide detection.On the basis of these studies,an effective method for the detection of pesticides under the condition of surfactant matrix was proposed and established by using ultra performance liquid chromatography-tandem quadrupole mass spectrometry.The main results of this paper are as follows:This method can be used to remove SDS without affecting the detection of pesticides.?1?The concentration of surfactants in pesticide samples is very low(such as SDS?20?g·L^-1),which also affects the chromatographic separation of pesticide samples to significantly inhibit the detection peak area of pesticides.The experiment also showed that the effect of SDS matrix effect could not be eliminated by pretreatment of the sample by solid phase extraction column LiChrolut EN,Oasis HLB and Isolute C18.?2?Based on the basic principle of liquid chromatography separation,a selective solid phase extraction method was proposed.The effects of four kinds of adsorbent quartz sand,calcite,kaolin and alumina on SDS adsorption strength were analyzed.The strength of adsorption of the four adsorbents for pesticide depends on the type of pesticides,the type and surface area of the adsorbents.It is noteworthy that pesticide concentration below 200?g·L^-1,pesticides could not be adsorbed by quartz sand at pH 7.On this basis,it was determined that quartz sand was selected as the adsorbent for surface modification in order to selectively select the pesticide and surfactant for the purpose of eliminating the SDS matrix effect of the solution.?3?Four types of silylated silica particles with different surface hydrophobicity and functionality were examined for selective adsorption and removal of SDS from water samples.Modifiers have different properties,such as molecular structure,carbon chain length,and functional groups,which makes the modified quartz sand to adsorb SDS to exhibit different results.It was found that trimethylchlorosilane?TMCS?modified quartz sand was more suitable for adsorption of SDS.Use of 3g size 0.5¹0?m TMCS modified quartz sand could eliminate the effects of SDS matrix effects between 0 and180?g·L^-1 at pH 8.Indicating that the modified modified quartz sand method eliminates the effect of SDS matrix without affecting the subsequent determination of pesticide content.?4?On the basis of the above research,the optimized treatment method for the selective adsorption of SDS in the pesticide sample solution using trimethylchlorosilane?TMCS?modified quartz sand was studied.The use of ultra-high performance liquid chromatography-tandem quadrupole mass spectrometry in the selective pretreatment of the sample under this condition was established in the pesticide detection method to eliminate the surfactant SDS method.The 6 kinds of matrix water samples by adding equal concentrations of surfactant and pesticide solution in two concentrations(5?g·L^-1and 20?g·L^-1),after pretreatment with this selective solid phase extraction technique,the recovery of this method is more than 80%,indicating that this method is useful for selective adsorption and reproducibility of selective adsorption of SDS.