Single-walled carbon nanotube coated with Ponceau4R-doped over-oxidized polypyrrole as a sensitive sensor for voltammetric monitoring of salbutamol

Abstract

A sensitive voltammetric sensor is fabricated by the electrochemical oxidation of polypyrrole (PPy) on a glassy carbon electrode surface covered with a thin film of single-walled carbon nanotubes (SWCNT/GCE). Ponceau4R (P4R) used as an anionic dopant controlled the structure, stability, conductivity, and electrochemical properties of the PPy. The porosity and oxygen-containing active sites on the P4R-PPy/SWCNT/GCE were increased by over-oxidation of the PPy layer to achieve P4R-oPPY/SWCNT/GCE. Morphology features of the P4R-oPPY/SWCNT layer are thoroughly characterized using microscopy instruments. The salbutamol (SAL) voltammetric behavior is evaluated by P4R-oPPY/SWCNT/GCE and a mechanism for its electrochemical oxidation is proposed. Optimizing the important parameters in the electrode modification procedure, including the amount of SWCNT and electrochemically deposited P4R-oPPY, and SAL sensing steps such as the solution pH, potential and accumulation time of SAL are optimized precisely. At the best condition, a ~ 20 times enhancement of the SAL oxidation current was observed by P4R-oPPY/SWCNT modifier. Using P4R-oPPY/SWCNT/GCE, a wide two-part linear range of 0.02–10 μM with a detection limit of 6 nM is resulted in the electrochemical measurement of SAL. The P4R-oPPY/SWCNT/GCE with good reproducibility and stability succeeded in correctly measuring SAL in pharmaceutical and clinical samples.