Abstract
A fluorescence polarization immunoassay (FPIA) for the determination of imidacloprid (IMI) was developed with advantages of simple operation and short assay time. The haptens of IMI, acetamiprid (ACE), and thiamethoxam (THI) were conjugated with fluorescein isothiocyanate ethylenediamine (EDF) and 4′-Aminomethyl fluorescein (AMF), respectively, to prepare six fluorescence tracers. The conjugation of IMI hapten and EDF (IMI-EDF) was selected to develop the FPIA due to the largest fluorescent polarization value increase in the presence of anti-IMI monoclonal antibody. Under the optimum condition, the limit of detection, 50% inhibition concentration and detection range of the FPIA were 1.7, 4.8, and 1.7–16.3 μg/L, respectively. The cross-reactivities (CRs) with the analogs of IMI were negligible except for imidaclothiz with CR of 79.13%. The average recovery of spiked paddy water, corn and cucumber samples were 82.4–118.5% with the RSDs of 7.0–15.9%, which indicated the FPIA had good accuracy. Thus, the developed FPIA was a potential tool for the rapid and accurate determination of IMI in agricultural and environmental samples.
Highlights
Imidacloprid (IMI) [1-6(chloro-3-pyridylmethyl)-N-nitroimidazo-lidin-2-ylideneamine] is one of the ultra-efficient neonicotinoid insecticides, which operates as a competitor to postsynaptic nicotinic receptors in a central nervous system of the insect
Three haptens of IMI, ACE and THI were conjugated with EDF and Aminomethyl fluorescein (AMF), respectively (Figure 1), which yielded six fluorescent tracers (IMI-EDF, IMI-AMF, ACE-EDF, ACE-AMF, THI-EDF, and THI-AMF)
The tracers prepared by EDF (IMI-EDF, THI-EDF, and ACE-EDF) could bind with mAb 3D11B12E5 to increase the FP values, but the FP values of the tracers prepared by AMF (IMI-AMF, THI-AMF, and ACE-EDF) were not changed (Table 1)
Summary
Imidacloprid (IMI) [1-6(chloro-3-pyridylmethyl)-N-nitroimidazo-lidin-2-ylideneamine] is one of the ultra-efficient neonicotinoid insecticides, which operates as a competitor to postsynaptic nicotinic receptors in a central nervous system of the insect. IMI has been extensively used in agricultural product in many countries because of its excellent insecticidal effectiveness (Lee et al, 2001). IMI shows high toxicity to honeybees (Rebecca et al, 2020; Wang et al, 2020) and its residues have potentially hazardous for consumers and ecosystem (Ana et al, 2019; Zhang et al, 2020). It is necessary to monitor the IMI residual in agricultural and environmental samples. The instrument-based methods, such as high-performance liquid chromatography (HPLC) (Carretero et al, 2003; Saeedeh et al, 2020) and gas chromatography-tandem mass spectrometry (Su et al, 2017; Massara et al, 2018), have been widely used for the determination of IMI. Immunoassay, as a rapid detection technique, has been widely
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