Abstract
Oxadiargyl, which binds to the protoporphyrinogen oxidase IX to exhibit herbicide activity, is mainly used in the prevention of certain perennial broadleaved and grass weeds during the preemergence of rice in paddy fields. However, oxadiargyl affects the germination and seedling growth of rice, causing damage to the plant and reducing rice yield. Hence, monitoring fate and behaviour of oxadiargyl in rice paddy fields is of great significance. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation method coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established in paddy water, paddy soil, rice straw, paddy hull, and brown rice. We validated this method for the first time in the analysis of the dissipation dynamic and residues of oxadiargyl over two years (2015–2016) at three sites in China. The average recoveries of oxadiargyl ranged from 76.0 to 98.8%, with relative standard deviations of 3.5–14.0%. The dissipation curves for paddy soil fit to a first-order kinetic equation, revealing that oxadiargyl degraded rapidly in paddy soil with half-lives (t1/2) of 4.5–7.6 days. The final oxadiargyl residues in all samples remained below the detection limit and the maximum residue limit in China (0.02 mg kg−1) and Japan (0.05 mg kg−1) during the harvesting dates and were not detected in rice straw.
Highlights
Paddy rice is mainly grown under submerged conditions in hot and humid areas
These results revealed that the proposed method possessed good accuracy and repeatability for oxadiargyl residue analysis according to the standard of pesticide residue analysis established by the European Commission [33]
A modified QuEChERS sample preparation method coupled with high-performance liquid chromatography (HPLC)−MS/MS
Summary
Paddy rice is mainly grown under submerged conditions in hot and humid areas (e.g., monsoonalAsia). Paddy rice is a major alimentary crop that feeds over half of the world population [1,2]. The market production of paddy rice has increased over the years, this growth is not sufficient to cover the rapid growth of the global population [3]. The amount produced could be improved by eliminating ‘harmful factors’ such as pests, fungi, and weeds [4]. In this regard, weeds can be conveniently and efficiently managed by herbicide application in replacement of other physical, mechanical, and cultural control methods. The use of herbicides has resulted in the exposure of crops to environmental contaminants, causing pollution and food safety problems [5,6]
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