Trace determination of imidacloprid and its major metabolites in wheat‐soil system

Abstract

Trace analysis method is a reliable basis for studying the translocation and metabolism of imidacloprid used as an insecticide in wheat, and it clarifies whether biologically active metabolites including residual imidacloprid, have long-lasting insecticidal potency against wheat aphids under seed treatment during the entire growth period. In this study, a highly sensitive analytical method was established to determine the residues of imidacloprid and its six metabolites(5-hydroxy imidacloprid, imidacloprid olefin, imidacloprid guanidine, imidacloprid urea, 6-chloronicotinic acid, and imidacloprid nitrosimine) in wheat-soil systems, such as in wheat leaves, wheat ears, wheat grains, roots, and soil. All the compounds were extracted using an ACN:water (8:2, v/v) mixture and purified by dispersive solid-phase extraction. The average recoveries ranged from 74.4% to 109.5% for all matrices, with intra-and inter-day variations of less than 14.9%. The limit of quantitation was in the range of 0.001-0.005 mg/kg. The method is demonstrated to be sensitive and accurate for monitoring imidacloprid and its metabolites at trace levels during the entire growth period under field conditions.

Determination and Dissipation of Thiamethoxam and Its Six Major Metabolites in Spring Wheat and Soil

“…However, they were inefficient at removing chlorophyll and pigments. Regarding the SPE cleanup methods, the Carb layer in the NH 2 /Carb and Carb SPE column contains GCB, which is efficient in removing chlorophyll, lutein, and other pigments . In this study, the NH 2 -Carb cartridges exhibited lower recovery for DN-CLO in leaf samples, possibly due to the –NH 2 groups of the cartridges interacting with the DN-CLO groups, impeding elution.…”

“…Regarding the SPE cleanup methods, the Carb layer in the NH 2 /Carb and Carb SPE column contains GCB, which is efficient in removing chlorophyll, lutein, and other pigments. 23 In this study, the NH 2 -Carb cartridges exhibited lower recovery for DN-CLO in leaf samples, possibly due to the −NH 2 groups of the cartridges interacting with the DN-CLO groups, impeding The efficiency of SPE depends on the type and volume of the elution solvent and, 26 thus in this study, different solvent volumes were tested (0, 2, 4, and 6 mL). The results showed that the recoveries of TMX and its metabolites were >80% when the eluent volume was 2 mL (Figure S3c).…”

“…Thus far, detection methods for DN-TMX, DN-CLO in water, and DM-TMX in wheat have been well established. , Most previous studies have only focused on the metabolite CLO and do not include other metabolites. − In this study, TMX and its six major metabolites were chosen as representatives. The majority of the reported methods focused on the modification of the QuEChERS method, which exhibited the limits of quantitation (LOQs) of 10.0 or even 50.0 μg/kg. ,, In this study, the solid phase extraction (SPE) purification method was effective in removing chlorophyll and pigments in wheat ear, leaf, and stem samples and afforded higher detection sensitivity. The LOQs of the method were as low as 1.0–5.0 μg/kg, meeting the requirements of trace analysis.…”

Insight into the Long-Lasting Control Efficacy of Neonicotinoid Imidacloprid against Wheat Aphids during the Entire Growth Period

“…Imidacloprid and its six main metabolites (5-hydroxy imidacloprid, imidacloprid olefin, imidacloprid nitrosimine, imidacloprid guanidine, imidacloprid urea, and 6chloronicotinic acid) in wheat-soil systems including wheat leaves, wheat ears, roots, and soil were analyzed according to our previously developed method. 13 Briefly, each sample (5 g) was placed in a 50 mL centrifuge tube to which 100 μL of 2.5 mg/L imidacloprid-D 4 solution was added and vortexed for 1 min. Subsequently, the sample was extracted by 10.0 mL of an acetonitrile and water mixture (v/v = 80/20) by vigorously shaking for 5 min.…”

“…Imidacloprid (IMI) is a commonly used systemic insecticide effective against plant aphids, white flies, and hoppers by seed treatment, foliar application, and soil treatment in many edible vegetables and staple crops. − Specially, it is widely used as a seed coating agent, which exhibits a long-term control efficacy (e.g., 7 months) against wheat aphids, implying that the dosage and frequency of insecticide application could be reduced. − In China, 10–15 million hectares are infested with cereal aphids, resulting in 10% yield losses annually, , where the wheat aphids Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius) are the predominant pests on wheat crops . Surprisingly, previous studies reported that the concentration of imidacloprid in wheat leaves at the later growth stage was close to its LC 10 value for aphids under seed treatment, while the control effect against wheat aphids was still higher than 80%. , Therefore, it is interesting to understand how this insecticide possesses such an excellent long-term performance even at a very low concentration in plant levels; however, so far, the underlying mechanism is still poorly understood.…”