Indirect Competitive Chemiluminescent Enzyme Immunoassay Method for Determination of Dimethyl Phthalate in Soy Sauce and Liquor

4-Amino dimethyl phthalate (ADMP) as hapten was coupled to carrier protein and subsequently used to immunize New Zealand rabbits. Polyclonal antibody which showed specific binding to dimethyl phthalate (DMP) was obtained, and on the basis of this, an indirect competitive chemiluminescent enzyme immunoassay (icCLEIA) was developed. The experimental parameters for icCLEIA were optimized as follows: the concentration of coating antigen was 50 mu g L-1, the primary antibody concentration was 92.5 mu g L-1, the secondary antibody concentration was 1 mu g mL(-1), ultrapure water (pH 6.0) was used as dilution solution and the time for competitive reaction was 40 min. Under the optimal conditions, the icCLEIA exhibited a linear working range from 0.74 mu g L-1 to 30.32 mu g L-1, with the limit of detection of 0.29 mu g L-1. The cross-reactivity with thirteen structural analogues was less than 5%. The recoveries of DMP from spiked liquor and soy sauce samples were from 80.2% to 116% and the average RSD was less than 3.6%. The detection results of spiked liquor and soy sauce by icCLEIA were consistent with those by standard GC-MS method. The developed icCLEIA method exhibited a practical potential for detecting DMP residue in food samples.