Study On Analytical Methods And Dissipation Pattern Of Polyethoxylated Tallow Amines Pesticide Adjuvant

Pesticide adjuvant,other than active ingredient,is added to the commercial pesticide formulations to enhance and improve the physical and chemical properties of the products.Polyethoxylated tallow amine(POE-tallowamine)is a class of synthetic surfactants widely used as pesticide adjuvant in commercial glyphosate formulations in the world,accounting for 3-18%in the glyphosate formulations.POE-tallowamine can improve the plant coverage and penetration of glyphosate through surface tissues.POE-tallowamine have been demonstrated reproductive toxicity,genotoxicity and hepatotoxic effects in a great number of studies.POE-tallowamine is ubiquitous in various matrices,including soil,sediment and mammals such as European brown hares.Considering the concerns about the toxicity of POE-tallowamine and their potential adverse effect on human health,POE-tallowamine has been listed as a co-formulant which is not accepted for inclusion in plant protection products by the European Union(EU).The US Environmental Protection Agency(EPA)and Canada have recently limited the additive dose of POE-tallowamine less than 25%and 20%in pesticide formulations,respectively.The widespread application of glyphosate formulations increased the potential pressure and risks to the environment and the health of human beings.However,there is a dearth of knowledge about the use and residues of POE-tallowamine in China.In this study,reliable analytical methods of comprehensive quantitative analysis of POE-tallowamine homologs in citrus and soil samples were established,respectively.Field trials and laboratory tests were conducted simultaneously to explore the residues and the dissipation regularity of POE-tallowamine in soil.The main contents are as follows:(1)A method based on ultraperformance liquid chromatography(UHPLC)with electrospray mass spectrometry detection for quantitative analysis of 66 POE-tallowamine homologs in pesticide formulations was described.Efficient separation of POE-tallowamine homologs with different degrees of saturation and ethoxylate units was achieved by employing a acetonitrile-aqueous solution containing 10m M ammonium formate gradient on a HILIC column.The distribution profiles of POE-tallowamine homologs in commercial POE-tallowamine adjuvants and glyphosate formulations were observed by the method.The detection rate of POE-tallowamine with different contributions in glyphosate formulations was about 45.4%.However,it should be noted that the detection rate of POE-tallowamine in the dust powder and granule was 62.5%.(2)A new method based on a modified Qu ECh ERS method and UHPLC with electrospray mass spectrometry detection for comprehensive quantitative analysis of POE-tallowamine homologs in citrus was established.The average recoveries of the POE-tallowamine homologs ranged from 71.9 to 112%,with RSDs<16.6%at the spiked level of POE-5(50,200,500μg/kg)and POE-15(250,1000,2500μg/kg).The limits of detection(LODs)and limits of quantification(LOQs)for POE-tallowamine homologs in citrus were 0.01-2.57 and 0.03-8.58 μg/kg,respectively.Quantitative accuracy and precision of the method were improved by the use of matrix-matched calibration standards(R~2>0.9900).The method was successfully applied to determine POE-tallowamine in citrus samples from Chinese main citrus producing areas in 2021.POE-tallowamine homologs were detected in all samples.The total concentrations of POE-tallowamine ranged from 48.5 to 143μg/kg,and the highest concentration was found in in Jelly orange from Zhejiang province.(3)A rapid and sensitive method based on alkaline digestion,modified Qu ECh ERS and UHPLC with electrospray mass spectrometry detection for comprehensive quantitative analysis of POE-tallowamine homologs in soil was established.Soil samples were treated with sodium hydroxide solution to rupture the strong adsorption between POE-tallowamine homologs and soil.At the spiked level of POE-5(40,200,400μg/kg)and POE-15(200,1000,2000μg/kg),the average recoveries of the POE-tallowamine homologs were ranging from 60.9%to 101%,with RSDs<12.8%.The LODs and LOQs for POE-tallowamine homologs were 0.003-1.12 and 0.01-3.73 μg/kg,respectively.The linearities of all the POE-tallowamine homologs were evaluated by analyzing matrix-matched standard solutions,and the correlation coefficients(R~2)were higher than 0.9900.The newly developed method was successfully applied to the analysis of the POE-tallowamine homologs in soil samples collected from Chinese main citrus producing areas.The POE-tallowamine was detected in all 66 samples.The total concentrations of POE-tallowamine ranged from 5.52 to 199μg/kg,and the highest concentration(199μg/kg)of POE-tallowamine was found in Zhejiang province.(4)Field trials and laboratory tests were conducted simultaneously.Temperature and microbial population were the key factors in the soil degradation of POE-5 under laboratory condition.Half-lives of POE-5 were 9.63-30.1 d,3.54-11.7 d and 3.30-9.50 d at different temperature(15℃,25℃ and 35℃),respectively.The degradation rates decreased with the increase of ethoxylate units.Half-lives of POE-5in sterile soil were 12.2-57.8 d,significantly higher than that in no sterile soil.Besides,the degradation rate of C18u was significantly higher than C16s and C18s.Similar results were found in field trials.The dissipation rates of POE-tallowamine in soil samples from Guangdong province were higher than those of Zhejiang province.