| Summary: | Chlorpyrifos, an organophosphorus insecticide that is widely used in pest control. This study focuses on the chlorpyrifos residue and degradation behaviour in spinach (Spinacia oleracea) and soil. The soil analyses include the determination of particle size, pH, percentage moisture and total organic carbon. The pH of soil was 4.95 with the content of 4.06 gkg-1 organic carbon, 15.55% moisture and 65.58% fine sand. A liquid-liquid extraction using acetone and water (70:30, v/v) followed by UV-Vis Spectrophotometer technique was performed to determine the residues of chlorpyrifos. The maximum absorbance (λmax) of chlorpyrifos was observed at 229 nm. Exponential relations were found to fit the first-order rate equation. Results had also shown that chlorpyrifos degradation equation in spinach was C=2.112e-0.09993t with a half-life (T0.5) of 6.93 days and R2 = 0.99383. The rate equation for degradation of chlorpyrifos in the soil sample was C=2.102e-0.01653t with R2 = 0.99383 and T0.5= 42.09 days. When chlorpyrifos formulations were applied according to the recommended dose, the final residues in both samples exceeded the Codex Alimentarius Commission (CODEX) maximum residue limit of 1 mgkg-1. Therefore, this work suggested that the harvest interval should be more than 14 days, which considered as safe to animal and humans. © 2015, Malaysian Society of Analytical Sciences. All rights reserved.
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