Dynamics of botanical fungicide 1% osthol EW residue in cucumber and soil.

A field experiment was conducted to reveal the dynamics of osthol residue in cucumber and soil.The osthol was extracted from the cucumber and soil by methanol and acetone,followed by liquid-liquid partition with petroleum ether,purification with solid phase extraction(SPE),and quantification with high-performance liquid chromatography(HPLC).The limit of detection(LOD) was 0.2 ng,while the limits of quantification(LOQ) of osthol both in cucumber and soil were 0.02 mg/kg.The average recoveries and coefficient of variations of osthol in cucumber were 88.80%-93.61%,1.94%-4.92%,respectively,and were 90.74%-94.55%,3.20%-6.45% for soil samples,respectively.The results of two-year field experiment showed that the half-lives of osthol were in a range of 0.76-0.87 d in cucumber and 1.12-1.15 d in soil.When the cucumber were treated with 1% osthol EW of 4 500 g/hm2 and 3 000 g/hm2 for five to six times,the final residues of osthol were 0.11-0.43 mg/kg in cucumber and 0.31-0.77 mg/kg in soil one day after treatment,which implied that osthol belonged to non-persistent pesticides and was easy to be degraded(T1/230 d).