Construction and Analytical Application of a Novel Ion‐Selective Capacitive Sensor for Determination of Cinchonine

Abstract

An ion‐selective capacitive sensor was constructed and applied to determine the concentration of cinchonine (CCN). The ion‐pair complex of cinchonine–picrolonate was embedded in electropolymerized o‐phenylenediamine film on gold electrode surface as a specific sensing element for the analysis of CCN. The logarithm of the capacitance change was linear, with the logarithm of CCN concentration in the range of 2.5 × 10⁻⁷ mol dm⁻³ ∼ 1.25 × 10⁻⁵ mol dm⁻³ with a detection limit of 1.0 × 10⁻⁷ mol dm⁻³ at pH = 7. The adsorption model of CCN onto ion‐selective film appears to be of the Langmuir type, and the adsorption equilibrium constant was estimated at 5.73 × 10⁵ dm³ mol⁻¹.

Keywords:

• Capacitive sensor
• Ion‐selective film
• Cinchonine
• Adsorption equilibrium constant

Acknowledgment

The author is grateful to Prof. Shouzhuo Yao (Hunan University, P. R. China) for his kindly suggestion. This work was supported by the Natural Science Foundation of Education Institution of Jiangsu Province (No. 03KJB150003), P. R. China.