Development of a Residue Analysis Method for Metamifop in Paddy Water, Soil, and Rice with HPLC

Abstract

An analytical method for detecting metamifop residue in paddy water, soil, and rice with high performance liquid chromatography (HPLC) was developed. Water was extracted with ethyl acetate before analyzing by HPLC. Soil residues were extracted with acetone under acidic condition and after purifying with Extrelut ® NT, and silica SPE, the residue was analyzed by HPLC. For residue analysis in rice, the procedure involved extraction with acetone, purification with Extrelut ® NT, partitioning between acetonitrile/hexane, purification with silica SPE cartridge, and analysis by HPLC. The limit of detection (LOD) was 1.0 ng, limit of quantitation (LOQ) was 3.0 ng, and method limit of quantitation (MLOQ) were 0.001 mg/L for paddy water, 0.01 mg/kg for rice and soil, respectively. Standard calibration curve shows linearity from 0.05 mg/kg to 5.0 mg/kg (R 2 = 0.9999). The recoveries in fortified paddy water were 91.3 ± 3.5% (0.01 mg/L level) and 93.2 ± 6.3% (0.05 mg/L level). The recoveries in fortified paddy soils were 92.5 ± 4.0% (0.1 mg/kg level) and 92.7 ± 4.0% (0.5 mg/kg level) in soil A, while, 102.3 ± 4.4% (0.1 mg/kg level) and 98.9 ± 7.9% (0.5 mg/kg level) in soil B, respectively. The recoveries in fortified rice were 93.0 ± 6.9% (0.1 mg/kg level) and 85.0 ± 3.5% (0.5 mg/kg level). This method was proved to be effective and can be used to determine the metamifop residue in paddy water, paddy soil, and rice.