Sensitive Determination of Toxic Clenbuterol in Pig Meat and Pig Liver Based on a Carbon Nanopolymer Composite

Abstract

The acidified single-walled carbon nanotubes (SWCNTs) were self-assembled on graphene oxide (GO) and then ultrasonically dispersed in a copolymer, Nafion solution, to form a GO/SWCNTs-Nafion polymer nanocomposite, which was employed to modify glassy carbon electrode (GCE). The surface morphological characteristics of different modified electrodes including bare GCE, GO-Nafion/GCE, and GO/SWCNTs-Nafion/GCE were imaged by scanning electron microscopy. For comparison, the differential pulse voltammetry and cyclic voltammetry behaviors were investigated, showing that the GO/SWCNTs-Nafion polymer composite has strong enhancement effect towards oxidation of clenbuterol (CLB). And the corresponding mechanism has been well discussed. During the reaction process, the anilino group of CLB molecule (1) was firstly oxidized to form a radical cation (2), exhibiting a characteristic oxidation peak (I) at 0.95 V, then two radical cations reacting via head-to-head coupling to form a diphenylamine intermediate (3), which was transformed into a CLB dimmer (4) through an azo bond by intramolecular electrons transferring under low potential, exhibiting a pair of reversible oxidation peak (II) and reduction peak (III). Under the optimum conditions, the composite modified electrode showed linear response to CLB in a concentration range of 1.0 × 10−8~6.0 × 10−6 mol/L with a detection limit of 6.0 × 10−9 mol/L. The modified electrode possessed good selectivity, reproducibility, and stability. In comparison with two routine analytical methods like ELISA kit and high-performance liquid chromatography (HPLC), the electrode can be successfully applied to determination of content of CLB in pig meat and pig liver samples with a recovery rate of 96.4~104.2%, suggesting a promising application in food security field.