An ionic liquid-type multiwall carbon nanotubes paste electrode for electrochemical investigation and determination of morphine

The direct electrochemistry of morphine on modified multiwall carbon nanotubes using carbon ionic liquid (i.e., 1-butyl-3-methylimidazolium hexafluoro phosphate, ([C4mim]–[PF6])) was studied. It was found that the electrode showed sensitive voltammetric response to morphine. The experimental results suggested that the modified electrode promoted electron transfer reaction for the oxidation of morphine. The electron transfer coefficient and charge transfer resistant (Rct) of morphine at the modified electrode were calculated. Under the optimized conditions at pH 8.0, the peak current was linear to morphine concentrations over the concentration range of 0.45–450 μmol L−1, using differential pulse voltammetry. The detection limit was 0.14 μmol L−1. The proposed method was successfully applied to the determination of morphine in both ampoules and urine samples.