A glassy carbon electrode modified with silver nanoparticles and functionalized multi-walled carbon nanotubes for voltammetric determination of the illicit growth promoter dienestrol in animal urine

An electroanalytical method for determining dienestrol (DNL) in bovine urine samples is described. A glassy carbon electrode (GCE) modified with silver nanoparticles and functionalized multi-walled carbon nanotubes was used as working sensor. The modified GCE displays substantial analytical improvements including an amplified signal, fast electron transfer kinetics, and resistance to fouling. The irreversible oxidation signal of DNL is pH-dependent. Best reactivity is found at pH3.0, where a typical anodic peak is recorded at 0.8V (vs. Ag/AgCl). Square-wave voltammetry revealed a 8.4nM detection limit (1.9 mu gL(-1)), good repeatability and reproducibility (RSDs <5.0%), and good accuracy (93.2-99.4% recovery from spiked samples). The modified electrode is highly stable even in the presence of ions (Na+ and K+), urea and uric acid. The electrochemical sensor fulfills all requisites to be used as forensic device in surveillance of illegal livestock practices.