Simultaneous Detection Of Amide Herbicides And Their Intermediates In Water And Beer Coupled With Gas Chromatography-mass Spectrometry

The sales volume of amide herbicides is ranked third in the global pesticide market.At present,the larger amount of production are propanil,acetochlor,alachlor,propisochlor,metolachlor,thiobencarb,butachlor and pretilachlor.Among these herbicides,the intermediate of acetochlor,metolachlor and thiobencarb is MEA(2-ethyl-6-methylaniline);the intermediate of propanil,alachlor and propisochlor is DEA(2,6-diethylaniline).And MEA and DEA can be degraded and generated from some of these amides herbicides by some microbes.Thus,the presences of these two intermediates in nature may have a certain relationship with the amides herbicides.Amides herbicides and aniline intermediates both are carcinogenic,teratogenic and mutagenic.This two types of substances may affect the quality and safety of agricultural products by pesticide spraying,residues in soil and water pollution caused by the pesticide production enterprises,which can threaten the health of human beings.Amide herbicides are widely used in beer producing areas in China,but the related detection methods are only aimed at barley rather than beer products.Therefore,it is very necessary to further study and detect the amide herbicides and their intermediates.At present,there are many studies on amide herbicides in water,and relatively few studies on aniline intermediates.There is still no report on the simultaneous detection of this type of herbicides and their intermediates.Most of the domestic and foreign analysis methods of pesticide residues are used for grape,fruit wine and white wine.Less relevant methods are used to detect beer and they do not refer to amide herbicides and their intermediates.Therefore,it is very important to establish the methods of simultaneous detection of pesticides,intermediates and degradation products.These methods can be applied not only to the detection of wastewater from pesticide plants,but also to the testing of environmental water and food quality and safety.This experiment is to use gas chromatography-mass spectrometry combined with liquid-liquid extraction and solid-phase extraction to detect amide herbicides and aniline intermediates in water and only with solid-phase extraction to detect them in beer.The main research contents and results are as follows:1.The main factors affecting liquid-liquid extraction(LLE)in water were the kind of extraction solvent,the volume of extraction solvent,pH value and the dosage of salt.Under these optimum conditions,this method showed good linear range in 0.1-20 ?g/L and had high recoveries(92.6%-110.3%)and correlation coefficients(0.9990-0.9999),low limits of detection(6.56-22.91 ng/L)and good reproducibility with relative standard deviations(3.4%-6.4%,n=7)at the spiked levels of 0.1,1 and 10 ?g/L.Therefore,this method was demonstrated to be accurate and feasible.2.The main factors influencing solid-phase extraction(SPE)in water were discussed such as the kind of SPE cartridge,type and ratio of elution solvent,volume of solvent,pH value of beer sample,as well as flow rate of beer and elution,were studied and optimized in detail.Under these optimum conditions,this method was linearity over the range of 0.1-20 ?g/L and had high recoveries(83.2%-114.2%)and correlation coefficients(0.9991-0.9996),low limits of detection(2.60-10.85 ng/L)and good reproducibility with relative standard deviations(2.5%-5.6%,n=7)at the spiked levels of 0.1,1 and 10 ?g/L.It indicated that this method was able to meet the precision and accuracy of pesticide residue detection.3.Some important extraction parameters of solid-phase extraction(SPE)in beer,such as volume of beer,the kind of SPE cartridge,type and ratio of elution solvent,volume of solvent,pH value of beer sample,as well as flow rate of beer and elution,were studied and optimized in detail.In the range of 0.1-20 ?g/L,this method had good linear relationships,the correlation coefficients were able to reach 0.9990 to 0.9996 and the limits of detection ranged between 2.37 and 10.28 ng/L.At the spiked levels of 0.1,1 and 10 ?g/L,the average recoveries were 92.1%-113.9%,and relative standard deviations(RSD)were 2.6%-5.4%,which manifested that the developed method could be used in the detection of amides herbicides and their intermediates in beer.4.The reservoir water and lake water were tested by liquid-liquid extraction and solid-phase extraction.The laboratory results showed that none of 10 target objects in the reservoir water was found and just acetochlor was detected in the lake.None of related target was found by liquid-liquid extraction in domestic sewage.In these three samples,the target objects of the concentrations of 0.2 ?g/L,2 ?g/L and 20 ?g/L were added to the target materials,and the accuracy and stability of this method were further certified.The optimized solid phase extraction method had been used to detect another three brands of beer.The experimental results showed that none of the three beers contained ten targets.In these three beer,0.2 ?g/L,2 ?g/L and 20 ?g/L in the concentrations of the targets were added for the standard recovery test.It proved that this method could be stablely and accuratly applied to the detection of different brands of beer.