Simultaneous electrochemical determination of levodopa and piroxicam using a glassy carbon electrode modified with a ZnO–Pd/CNT nanocomposite

A highly conductive electrochemical sensor was constructed for the simultaneous electrochemical determination of levodopa and piroxicam by modification of a glassy carbon electrode with a ZnO-Pd/CNT nanocomposite (GCE/ZnO-Pd/CNTs). The ZnO-Pd/CNT nanocomposite was synthesized by the sol-gel procedure and was characterized by EDAX, MAP and SEM. The sensor was shown to improve the oxidation signal of levodopa and piroxicam by ∼70.2-fold and ∼41.5-fold, respectively. This marks the first time that the electrochemical behavior of levodopa and piroxicam have been investigated at the surface of GCE/ZnO-Pd/CNTs. The voltammogram showed a quasi-reversible signal and an irreversible redox signal for electro-oxidation of levodopa and piroxicam, respectively. The GCE/ZnO-Pd/CNTs showed a linear dynamic range of 0.6 to 100.0 μM (at a potential of ∼180 mV) and 0.1 to 90 μM (at a potential of ∼480 mV) with detection limits of 0.08 and 0.04 μM for the determination of levodopa and piroxicam, respectively. GCE/ZnO-Pd/CNTs were then applied for the determination of levodopa and piroxicam in real samples.