Determination of Dimethachlon in Tobacco by Time-resolved Fluorescence Immunoassay

A sensitive time-resolved fluorescence immunoassay (TRFIA) with a cleanup-free pretreatment for dimethachlon in tobacco was developed. The competitive indirect TRFIA for dimethachlon was established by using goat anti-rabbit IgG conjugated with a Eu-N1 clelate as a tracer. The detection limit (I-10) and I-50 for this assay was 1.98 mu g/L and 32.00 mu g/L, respectively. And the linear range for detection is between 3.97-128.76 mu g/L. Meanwhile, the effect of tobacco matrix to TRFIA was also studied. It was demonstrated that the linear range of inhibition curve with 1% tobacco matrix was parallel to the standard curve; so the extract of tobacco would be diluted 100 times before assay, the index of matrix interference (I-m) was calculated as 17.1. Three levels of dimethachon (1, 7 and 24 mg/L) were spiked into tobacco, the overall recoveries and the relative standard deviations (RSDs) were in the range of 73%-128% and 4.3-13.2, and the practical detection limit for the method was 1 mg/L. This assay is a suitable tool for screening dimethachlon residue in tobacco samples