Voltammetric determination of isoproterenol using multiwall carbon nanotubes-ionic liquid paste electrode

A sensitive and selective electrochemical method for the determination of isoproterenol (ISPT) was developed using multiwall carbon nanotubes and a room temperature ionic liquid (i.e. 1-butyl-3-methylimidazolium hexafluoro phosphate, ([C4mim]-[PF6])). This multiwall carbon nanotubes ionic liquid electrode (MWCNTILEE) is a very good alternative to previously described electrodes because the electrocatalytic effect is achieved without any electrode modification. The oxidation peak potentials in cyclic voltammogram of ISPT on MWCNTILEE was occurred around 470 mV vs Ag/AgCl (at pH 6.0) while this peak potential at carbon paste electrode was appeared around 605 mV at the same scan rate of 100 mV s⁻¹. The electrochemical parameters such as diffusion coefficient and charge transfer resistance were determined using cyclic voltammetry and electrochemical impedance spectroscopy. Under the optimized conditions, the peak current was linear to ISPT concentration over the concentration range of 1.0 to 520 µmol L⁻¹ using differential pulse voltammetry. The detection limit was 0.85 µmol L⁻¹. The proposed method was successfully applied to the determination of ISPT in both ampoules and urine samples.