Study on residue decline dynamics of fluroxypyr in rice plant,rice and rice hull,paddy soil and water

Residue decline dynamics of fluroxypyr in rice plant,rice and rice hull,paddy soil and water was reported.Fluroxypyr in the samples was extracted with NaOH-methanol,purified with liquid-liquid extraction and detected by capillary gas chromatography with electron capture detector after methyl esterification.The results showed that the average recoveries in paddy plant,soil,water,rice and rice hull ranged from 85.5% to 103.2%,the RSD was from 1.9% to 9.9%,the limit of detection of fluroxypyr standard was 2.0×10-12g,and the limit of quantification in paddy plants,rice,rice hull,soil and water were 0.005,0.02,0.005,0.002 mg/kg and 0.001 mg/L,respectively.The test in Anhui and Guangdong Province in 2007 and 2008 indicated that the half-life of fluroxypyr were from 4.9 d to 6.0 d in plant,while in soil were from 5.5 d to 8.6 d,in water were from 11.0 d to 13.8 d.The final residues of fluroxypyr in rice were lower than Chinese MRL of 0.2 mg/kg.It was suggested that 5% WP of fluroxypyr should be applied to control weeds in rice field with the dosage less than 168.8 a.i.g/ha at period of seedling establishment.