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

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 (Eu 3   + )-labeled antibody, respectively. After optimization, the half-maximal inhibition concentration (IC 50 ) and the limit of detection (LOD, IC 10 ) 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).