Abstract: Coupled with the BSA, hapten MPA, used as a coating antigen，combined with anti-MPA polyclonal antibody with the competition of free MPA. Indirect competition ELISA was set up according to abovementioned mode to detect the residue level of MPA in the example. The results of the experiment demonstrates that the optimal concentration of the coating antigen was 0.75 μg/ml. Polyclonal antibody against MPA was 1∶8000 and the standard curve had a good linearity in the rang of 1~50 ng/ml with detection limit being 0.1 ng/ml. The regression equation y=1.1479x+0.9426(r2=0.9679) were obtained while the coefficient of variation of intraassay and extra-assay were 5.35%,10.89% respectively. 

Key words: ciELISA; half antigen; standard curve 