Simultaneous detection of imidacloprid and parathion by the dual-labeled time-resolved fluoroimmunoassay

A highly sensitive direct dual-labeled time-resolved fluoroimmunoassay (TRFIA) to detect parathion and imidacloprid simultaneously in food and environmental matrices was developed. Europium (Eu 3+ ) and samarium (Sm 3+ ) were used as fluorescent labels by coupling separately with L 1 -Ab and A 1 P 1 -Ab. Under optimal assay conditions, the half-maximal inhibition concentration (IC 50 ) and limit of detection (LOD, IC 10 ) were 10.87 and 0.025 μg/L for parathion and 7.08 and 0.028 μg/L for imidacloprid, respectively. The cross-reactivities (CR) were negligible except for methyl-parathion (42.4 %) and imidaclothiz (103.4 %). The average recoveries of imidacloprid ranged from 78.9 to 104.2 % in water, soil, rice, tomato, and Chinese cabbage with a relative standard deviation (RSD) of 2.4 to 11.6 %, and those of parathion were from 81.5 to 110.9 % with the RSD of 3.2 to 10.5 %. The results of TRFIA for the authentic samples were validated by comparison with gas chromatography (GC) analyses, and satisfactory correlations (parathion: R 2  = 0.9918; imidacloprid: R 2  = 0.9908) were obtained. The results indicate that the dual-labeled TRFIA is convenient and reliable to detect parathion and imidacloprid simultaneously in food and environmental matrices.