Competitive immunoassay by capillary electrophoresis with laser-induced fluorescence for the trace detection of chloramphenicol in animal-derived foods

A competitive immunoassay using CE with an LIF detector was developed for the detection of chloramphenicol (CAP). The method was based on the competitive reactions between fluorescently labeled CAP hapten and free CAP, with a limited amount of anti-CAP antibody. The poly (N-isopropylacrylamide) (pNIPA) hydrogel was added in the separation buffer as a dynamic modifier to reduce adsorption and enhance reproducibility. The linear range and LOD for CAP were 0.008-5 mu g/L and 0.0016 mu g/L, respectively. An ELISA using the same immuno-reagents was also developed for the analysis of CAP, with an LOD of 0.03 mu g/L. The sensitivity of this CE immunoassay (CEIA)-LIF was almost 20 times greater than that of the ELISA. Using CEIA-LIF, equilibrium was reached in 15 min and the analytical results-were obtained within 5 min by CE separation. Sample preparation for CEIA-LIF was not time-consuming and the matrix effect was easy to remove. An LOD of 0.1 mu g/ kg CAP in food matrices was easily achieved. This method is thus proposed as a fast and sensitive means of detecting trace amounts of CAP residues in animal-derived foods.