We have developed a new method of electrochemical immunosensor for the determination of ractopamine (RAC). The modified electrodes were prepared as follows. First, the multi-walled carbon nanotubes and ionic liquid composites were cast on glassy carbon electrode (GCE), and then the ractopamine-bovine serum albumin antigens were cast on GCE. At last, we dipped a few Nafion onto the electrode. Cyclic voltammetry and differential pulse voltammetry were employed to monitor the fabrication steps of immunoreaction system in solutions containing K₃Fe(CN)₆ as redox probes. The immunosensor demonstrates excellent RAC detection features with a broad linear range of 1 to 1500 ng/mL and a detection limit of 0.3 ng/mL. The tests with spiked animal feed samples showed excellent recovery for ractopamine.

Key words: multi-walled carbon nanotube, ionic liquid, ractopamine, electrochemical immunosensor