Recognition and Detection of METOL at an L‐Cysteine Modified Gold Electrode

Abstract

L‐Cysteine self‐assembled monolayer (SAM) modified gold electrode (L‐Cys/Au SAM) has been fabricated. Attenuated total reflection‐Fourier transform infrared spectrometer (ATR‐FTIR), scanning electron microscopy (SEM) and ac impedance were used to characterize the structure and electrochemical properties of the film. The voltammetric behavior of N‐methyl‐p‐aminophenol sulfate (METOL) has been studied on the gold electrode modified with SAMs of L‐cysteine. The voltammetric responses showed that the redox mechanism for METOL at the modified electrode is a reversible‐type mechanism. Its oxidation peak potential shifted 132 mV negatively and peak‐to‐peak separation was reduced to 42 mV. It indicated that L‐cysteine has electrocatalytic activity towards METOL and it can accelerate the electron transfer rate between METOL and electrode. Diffusion coefficient is 2.24 × 10⁻⁶ cm² s⁻¹. Differential pulse voltammetry (DPV) responses showed that catalytic current is linear with the METOL concentration in the range of 5.0 × 10⁻⁷–2.0 × 10⁻⁵ mol L⁻¹ and 5.0 × 10⁻⁵–1.0 × 10⁻³ mol L⁻¹, with the correlation coefficient 0.9987 and 0.9972. The detection limit is down to 1.0 × 10⁻⁸mol L⁻¹. The method was applied to determine the concentration of METOL in photographic solution, with satisfactory results.

Keywords:

• Self‐assembled monolayer
• L‐Cysteine
• METOL
• DPV

Acknowledgments

The financial support of the Natural Science Foundation of Hubei province of P. R. China (No. 2000J007) is greatly acknowledged.