We describe a method for the determination of cocaine that is based on a glassy carbon electrode modified with a nanocomposite consisting of multiwalled carbon nanotubes, an ionic liquid, and chitosan. A modified glassy carbon electrode (GCE) employed as the working electrode and a platinum wire as the counter electrode. All potentials were referred to an Ag/AgCl (satd. KCl) electrode. The electrode was made cocaine-responsive by immobilizing a cocaine-specific aptamer and platinum nanoparticles (PtNPs) on the modified electrode. The use of PtNPs resulted in the acceleration of the electron transfer kinetics of the reduction of the redox probe rutin and enhances sensitivity. The sensor has a linear response to cocaine in the 1 nM to 11 μM concentration range, and the detection limit is 100 pM (at an S/N ratio of 3). We think this strategy to represent a promising platform for the sensitive and selective determination of cocaine. The sensor also is adequately stable and was successfully applied to the determination of cocaine in spiked serum.
