Research On Degradation Prducts And Pathway Of Ethiporle In Different Environments

Ethiprole is a new 1-phenylpyrazole insecticide effective against a broad spectrum of sucking and chewing insects with pronounced plant systemic activity and widely uses on rice and stored grain insect pests. However, ethiprole is stable in the water, and has different degree of toxicity for organisms in the environment. Once ethiprole unreasonably applied to the environment, it is possible for threatening the ecosystems and human health. A method was developed to determine the ethiprole residue and identify its degradation products in soil and water. The study is focused on the investigation of environmental behaviors and the differences of degradation products of ethiprole in different environment. And the ethiprole degradation pathway was deduced in the entire environment. Meanwhile, the toxicity of the ethiprole degradation products were studied. The results are as follows:(1) A simple method for the determination of ethiprole residue in water and soil was developed by ultra-performance liquid chromatography coupled to quadrupole–time of flight mass spectrometry(UHPLC-QTOF/MS). Using excellent QuEChERS method, ethiprole was extracted by acetonitrile(containing 0.1%(v/v) acetic acid) and purified by Primary secondary amine(PSA). The results showed that the linearity was good in the ranges from 0.01 to 10 mg/L, and the regression equation was y=31560x-1055.2(R2 = 0.9994). Recovery studies were performed at four spiked levels of 0.01, 0.1, 1.0 and 10.0 mg/kg in blank soil and water, and the overall recoveries ranged from 80.2% to 105.5%. The data demonstrated the good repeatability of the method with relative standard deviations(RSDs) lower than 7.8 % for all analytes. The method is efficient and reliable for the determination of ethiprole residue in soil and water.(2) The degradation behaviors of ethiprole were studied in different environment.(1) The degradation of ethiprole in soil was mainly carried out in northern China black soil under aerobic and anaerobic conditions. The results showed: the degradation half-lifes of ethiprole in aerobic and anaerobic conditions were 20.4 d and 11.9 d, respectively. The degradation rate in anaerobic condition was significant faster than aerobic condition. The main influence factors of degradation rate were soil microbial species and quantity.(2) Hydrolysis of ethiprole was studied under the condition of different pH value and temperature. The results showed: At temperature of 15 ℃, the ethiprole was very stable in the water and pH 5,7. However, the degradation half-lifes of ethiprole in pH 9 was 187.29 d. At temperature of 25 ℃, the ethiprole was very stable in the water and pH 5,7. But the degradation half-lifes of ethiprole in pH 9 was 138.6 d. At temperature of 35 ℃, the ethiprole was stable in the water and pH 5. However, the degradation half-lifes of ethiprole in pH 7, 9 was 173.25 and 97.61 d, respectively. Therefore, the hydrolysis rate of ethiprole may be faster under the condition of alkaline than acidic. Temperature has a certain effect. The higher temperature, the quicker hydrolysis.(3) At the source of xenon( UV intensity 98.7 μW/cm2) and the temperature of 25 ℃, the photolysis half-lifes of ethiprole in pH 5, 7, 9 and ultrapure water were 17.33, 4.17, 3.69, 9.90 h. The pH has a certain effect. The higher the pH, the quicker photolysis.(3) The degradation mechanism of insecticide ethiprole were studied under the different environment in this paper. During ethiprole degradation, eleven degradation products were detected and identified by UHPLC-QTOF/MS. And two degradation products of newly discovery were 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-ethylsulfonyl-pyrazole and 5-amino-3-cyano-1-(4-trifluoromethylphenyl)-4-ethylsulfidepyrazole. Moreover, we speculated degradation pathway of ethiprole in the entire environment. The main possible pathway involved reduction reaction, hydrolysis reaction, oxidation reaction, oxidation dechlorination and the reaction of hydroxylation. And a simple method for the determination of three degradation products of ethiprole was developed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry(UHPLC-MS/MS).(4) Finally, in present paper, ethiprole as well as three degradation products in acute toxicity to Daphnia magna straus was studied. The results indicated there were significant differences between these compounds. As for the Daphnia magna straus., the degradation products of molecular weight of 401 was high toxicity, the degradation products of molecular weight of 312 and ethiprole were poisoning, and the degradation products of molecular weight of 399 was low toxicity. The degradation products of molecular weight of 401 was about 3 times more toxic than parent compound, and the degradation products of molecular weight of 312 was about 2 times more toxic than parent compound. The results show that some of the degradation products toxicity is higher than the parent compound. Therefore, we should strengthen the monitoring of some degradation products of ethiprole to reduce the harm and influence of non-target organisms.