A magnetic field controlled and disposable amperometric immunosensor was fabricated for determination of chloramphenicol (CAP) by carbon nanotube (CNT)/ferrocene(Fc)/Nafion-membrane coated on the screen-printed carbon electrodes (SPCE) and then GMP [Fe₃O₄(core)/Au(shell)] composite nanoparticle coated chloramphenicol-bovine serum albumin (CAP-BSA) was absorbed on it through external magnetic field. Scanning electron micrography (SEM) and X-ray fluorescence spectrometry (XRFS) were employed to characterize the construction process of the immunosensor. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study its electrochemical properties. The content of CAP was determined with competitive immunoassay. When CAP of different concentration was added in 25 μL of pH＝6.0 phosphate buffer solution (PBS) containing 100 ng•mL^－1 anti-CAP, the percentage of cathodic peak DPV current increase ratio (CI%) was proportional to the concentration of CAP over the range of 0.2～80.0 ng•mL^－1 after incubation for 6 min at 25 ℃. The detection limit was 0.11 ng•mL^－1. The immunosensor was employed to determine CAP in milk samples and the recovery rates exhibited a range of 88%～104%. The results were consistent to the tradition HPLC method. The proposed amperometric immunosensor was sensitive, quick, magnetic field controllable, low sample consumable and disposable, which was suitable for determining the trace chloramphenicol in food.

Key words: carbon nanotube, gold magnetic composite nanoparticle, disposable amperometric immunosensor, chloramphenicol, milk, magnetic field controlled