Direct competitive fluoroimmunoassays for detection of imidaclothiz in environmental and agricultural samples using quantum dots and europium as labels

•QDFIA and TRFIA were developed and applied to the monitoring of imidaclothiz.•QDFIA and TRFIA showed higher sensitivity than reported ELISA and FPIA.•Eight kinds of matrix were studied by spiked recovery experiment.•The amounts of imidaclothiz in real samples detected by QDFIA and TRFIA were correlated with that detected by HPLC.

A direct quantum dots-based fluoroimmunoassay (QDFIA) and a time-resolved fluoroimmunoassay (TRFIA) for imidaclothiz (IMI) were developed by using the quantum dots (QDs)-labeled antibody and the europium (Eu3 +)-labeled antibody, respectively. After optimization, the half-maximal inhibition concentration (IC50) and the limit of detection (LOD, IC10) are 20.41 and 0.52 μg L− 1 for the QDFIA, while 6.91 and 0.018 μg L− 1 for the TRFIA, respectively. The cross-reactivities (CRs) with the analogues are negligible except for imidacloprid with CRs of 29.0% for the QDFIA and 26.6% for the TRFIA. The spiked recoveries of IMI in paddy water, soil, pear, tomato, rice, apple, cabbage and cucumber are 72.7-117.6% with a standard deviation (RSD) of 2.4- 13.5% for the QDFIA, and 81.3-117.7% with a RSD of 1.6- 7.5% for TRFIA. The detection results of the analyses for the real paddy water and pear samples are markedly correlated with these of high-performance liquid chromatography (HPLC).

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