Dissipation of chlorpyrifos and residue analysis in rice, soil and water under paddy field conditions

The analytical method for the residues of chlorpyrifos in rice plants, water and soil was developed and dissipation of chlorpyrifos under field conditions was studied. The limit of detection (LOD) of chlorpyrifos was 0.006 mg kg−1 and the limit of quantification (LOQ) was found to be 0.04 mg kg−1 in rice plant (water) and 0.02 mg kg−1 in the other substrates, respectively. The results showed that the initial residues of chlorpyrifos in Nanjing and Guangxi were 4.99 and 6.05 mg kg−1 (rice plant), 1.35 and 1.58 mg kg−1 (water) and 0.51 and 0.63 mg kg−1 (soil), respectively. The half-lives of chlorpyrifos in rice plant, water and soil from Nanjing were 4.28, 0.58 and 1.35 day, respectively, and the half-lives of those from Guangxi were 3.86, 0.52 and 1.21 day, respectively. The husked rice, rice hull and straw samples were found to contain chlorpyrifos well below the maximum residue limit (MRL) following the recommended dosage, the residues of chlorpyrifos in soil were undetectable under all application levels and frequencies after 28 day of applications.

► The first study the residual dissipation and ultimate residue of 25% chlorpyrifos in the rice crops. ► The final chlorpyrifos residues were found well below the maximum residue limit (MRL) following the recommended dosage. ► The residues of chlorpyrifos in soil were undetectable under all application levels and frequencies with 28 days interval.