Establishment Of LC-MS Purification Method And Exposure Risk Assessment For Organophosphorus Herbicides In Tea

Tea is a widely consumed beverage and loved for both its various health benefits and its pleasant taste.Tea bushes grow in long-term tea gardens,which are equally suitable for continued weed growth in an environment that is increasingly controlled by herbicides.As a result,there are growing concerns that tea consumers may be exposed to herbicide residues.Glyphosate（PMG）,which has the characteristics of non-selectivity,high efficiency,and low cost,is currently the most widely used herbicide in the world.Glufosinate ammonium（GLU）is a non-selective,broad-spectrum contact herbicide,both of which are organophosphorus herbicides.Aminomethyl phosphonic acid（AMPA）is the main toxic metabolite of glyphosate.It has been reported that glyphosate and glufosinate have been detected in tea or tea products,and even exceeded the standard,affecting the quality and safety of tea.There is no report on the dietary exposure risk assessment of PMG,GLU and AMPA in tea,and it is not clear whether they constitute a risk to human health.At present,there are many kinds of methods for the analysis of PMG and GLU residues in tea,and there are problems such as cumbersome pretreatment process and high cost.In response to these problems,an HPLC-MS/MS method for the detection of glyphosate,glufosinate and aminomethylphosphonic acid in tea was established in this paper,and780 samples from 11 provinces in China were determined.According to the test results,the dietary exposure risk assessment of PMG,GLU and AMPA in tea was studied.The main research results are as follows:An HPLC-MS/MS method for the detection of glyphosate,glufosinate-ammonium and aminomethylphosphonic acid in tea was established.This method was compared with several current purification methods,which effectively reduce the interference caused by the tea matrix during the analysis.The established HPLC-MS/MS detection method was validated.The recovery rates of PMG,GLU and AMPA ranged from 89.6%to 115.5%,83.6%to 101.6%and 82.1%to 97.2%,respectively.The relative standard deviation（RSD）values were all below20%.This method was used to determine the levels of PMG,GLU and AMPA in 780samples,including six types of tea leaves and a flower tea,from 11 provinces of China.PMG,GLU and AMPA were detected in 9.0%,1.8%and 21.2%of the samples,respectively.The PMG levels ranged from 0.102 mg·kg^-1 to 2.647 mg·kg^-1,GLU from0.041 mg·kg^-1 to 1.428 mg·kg^-1 and AMPA from 0.107 mg·kg^-1 to 3.166 mg·kg^-1.According to the test results,the dietary exposure risk assessment of PMG,GLU and AMPA in tea was carried out.Probability estimates showed that the 95th percentile risk entropy value of the three pesticide residues were 2.39×10^-6,7.98×10^-5 and 1.96×10^-5,respectively,which are far below the acceptable risk level.The risk assessment results showed that exposure to PMG,GLU and AMPA caused by drinking tea beverages poses no significant risk to human health.