Dissipation Kinetics of Cyazofamid in Water

Residue behaviours, dissipation kinetics and dietary risk assessment of pyaclostrobin, cyazofamid and its metabolite in grape

BACKGROUND

Grape is an important fruit consumed either fresh or processed, therefore, fungicide misuse of grape has become an issue of global food safety and human health. Pyraclostrobin, and cyazofamid have been applied to grape frequently.

RESULTS

Here a simple QuEChERS (quick, easy, cheap, effective, rugged, and safe) liquid chromatography mass spectrometry technique has been developed and validated for the determination of pyraclostrobin, cyazofamid and its metabolite CCIM in open field grape samples. The recoveries of these three in the range of 0.01 to 5 mg kg^-1 (n = 5) ranged from 73.1% to 97.9%. The relative standard deviations (RSDs) were below 12% for all cases. The limits of quantitation of each analyte was 0.005 mg kg^-1 , which was lower than maximum residue limits of not only pyraclostrobin but also cyazofamid. Not only dissipation kinetics but also residue determination was obtained in grape for those three pesticides. Furthermore, their half-lives in grapes were 10.7-30.1 days, recommending the pre-harvest intervals for these three of 14 days. The calculated hazard quotient and acute hazard index lower than 100% illustrated the safety of intake of grape for the Chinese population for not only long-term but also short-term dietary risk assessment.

CONSLUSIONS

The less than 30 day half-life illustrated that pyraclostrobin and cyazofamid could degrade relatively easily in the environment. The long-term and short-term dietary risk assessment also illustrated the intake safety of these three. Thus, a 14 day pre-harvest interval was safe and recommended. The results of this study contributed to environmental protection, food safety and human health. © 2019 Society of Chemical Industry.

Coating polystyrene beads with iron oxide for the adsorption of carbofuran from the water supply

Population growth requires more food production and as a consequence, there is the indiscriminate use of agrochemicals, among them major group are carbamates. At times, runoff of pesticides leads to surface water pollution that serves as a source of public supply. Thus, the presence of these microcontaminants in surface water has become increasingly frequent. The treatment developed in this work uses the principle of adsorption as a technology for the removal of carbamates, more specifically carbofuran. Two methods of coating the polystyrene beads with iron oxide were used to adsorb these microcontaminants from the water. The coating was evaluated through the chemical extraction of iron, analysis by scanning electron microscopy and BET analysis. The metallurgy that presented the best coating was the one that used the ferric chloride. The beads coated by this methodology were used for adsorption tests of carbofuran and showed positive results after verification of the influence of pH on the adsorption process.

The dissipation of cyazofamid and its main metabolite in soil response oppositely to biochar application

Biochars derived from rice straw (RS), corn straw (CS), chicken manure (CM) and tire rubber (TR) were applied to soil to investigate their effects on the dissipation of cyazofamid and its metabolite CCIM (4-chloro-5-p-tolylimidazole-2-carbonitrile), with high acute toxicity compared to cyazofamid. The enhancement of cyazofamid dissipation followed the order of CS > RS > CM, whereas TR depressed the cyazofamid dissipation. Adsorption, hydrolysis and microbial degradation were all involved in cyazofamid dissipation. CM and CS enhanced the contribution of biodegradation to cyazofamid dissipation, which might be related with the shifted microbial community. More importantly, CCIM residual was drastically increased by 8-15 times after biochar application, regardless of biochar type. In total, this study shed light on the issue of build-up of metabolites in biochar-amended soil, especially for metabolites having higher toxicities than parent compounds, providing new insights into potential risk of biochar application for soil remediation.

Simultaneous determination of residues of metalaxyl, cyazofamid and a cyazofamid metabolite in tobacco leaves and soil by liquid chromatography with tandem mass spectrometry

A simple method was developed and validated for the simultaneous determination of metalaxyl, cyazofamid and the cyazofamid metabolite 4-chloro-5-p-tolylimidazole-2-carbonitrile (CCIM) by liquid chromatography with tandem mass spectrometry. The three target compounds were extracted from tobacco and soil with acetonitrile containing 0.1% acetic acid, and the extracts were purified using octadecylsilane. The proposed method showed satisfactory linearity (R2 ≥ 0.9985) for the target compounds. The limits of detection for metalaxyl, cyazofamid and CCIM were 0.006, 0.06 and 0.06 mg/kg in soil and green tobacco leaves and 0.03, 0.3 and 0.3 mg/kg in cured tobacco leaves, respectively. The limits of quantification for metalaxyl, cyazofamid and CCIM were 0.02, 0.2 and 0.2 mg/kg in soil and green tobacco leaves and 0.1, 1 and 1 mg/kg in cured tobacco leaves, respectively. The average recoveries from soil and tobacco were 72.91-98.40% for metalaxyl, 76.73-105.80% for cyazofamid and 74.48-106.45% for CCIM. The relative standard deviation range was 1.23-6.99%. The developed method was successfully applied to analysis of residues of metalaxyl, cyazofamid and CCIM in real soil and tobacco samples. The results indicated that the established method could meet the requirement for the analysis of trace amounts of all three analytes in soil and tobacco.