Electrochemical behavior and determination of fluphenazine at multi-walled carbon nanotubes/(3-mercaptopropyl)trimethoxysilane bilayer modified gold electrodes.

A novel multi-walled carbon nanotubes/(3-mercaptopropyl)trimethoxysilane (MPS) bilayer modified gold electrode was prepared and used to study the electrochemcial behavior of fluphenazine and determine it. Fluphenazine could effectively accumulate at this electrode and produce two anodic peaks at about 0.78V and 0.93V (versus SCE). The peak at about 0.78V was much higher and sensitive, thus it could be applied to the determination. Various conditions were optimized for practical application. Under the selected conditions (i.e. 0.05M pH 3.5 HCOOH-HCOONa buffer solution, 5mul 1mgml(-1) multi-walled carbon nanotubes for Phi=2.0mm electrode, accumulation at open circuit for 180s), the anodic peak current was linear to fluphenazine concentration in the range from 5x10(-8) to 1.5x10(-5)M with correlation coefficient of 0.9984, the detection limit was 1x10(-8)M. For a 1x10(-5)M fluphenazine solution, the relative standard deviation of peak current was 2.51% (n=8). This method was successfully applied to the determination of fluphenazine in drug samples and the recovery was 96.4-104.4%. The electrode could be easily regenerated and exhibited some selectivity, but some surfactants reduced the peak current greatly. The modified electrode was characterized by alternating current impedance and electrochemical probe.