Immuno-voltammetric Determination of Chloramphenicol Residues in Milk

To investigate the immunovoltammetric techniques with high sensitivity and specificity for the determination of chloramphenicol (CAP) residues in milk, the conjugate of ovalbumin (OVA)-CAP was immobilized onto the micro-reaction plate and the monoclonal anti-chloramphenicol antibody was prepared to set up competitive enzyme-linked immunoabsorbent assays (ELISA). After the procedure of competitive combination of OVA-CAP and CAP in sample with anti-chloramphenicol monoclonal antibody during the incubation period, the plate was rinsed and alkaline phosphatase (ALP)-labeled goat anti-mouse IgG was added into the microcuvettes. p-nitrophenylphate was applied as substrate after the second incubation and then rinsed. The oxidative peak currents (OPC) were recorded by differentiated pulse voltammetry (DPV) after the reaction on the plate, which was terminated by the addition of 2 M NaOH. The results showed that the sensitivity of immunovoltammetry was better than that of ELISA for determination of CAP residues. This method allows the detection limit as low as 0.064 μg l−1 with the linear range of 0.15–600 μg l−1 CAP, and the average recovery reaches 89.8% based on the milk sample. Furthermore, the immunovoltammetric apparatus is portable and can be used for the on-spot determination of CAP residues in milk due to its small size and easy operation.