Determination of ferulic acid based on the L-cysteine self-assembled modified gold electrode coupling irreversible biamperometry

L-cysteine self-assembled monolayer modified electrode (L-Cys/SAM -Au/CME) has been fabricated on the surface of bare gold wire. The electrochemical behaviors of ferulic acid on the modified electrode were studied. The method of self-assembled monolayer modified electrode was applied to establish the flow-injection irreversible biamperometric analysis. Namely, the irreversible system is composed of electrocatalytic oxidation of ferulic acid at one L-cysteine gold modified electrode and reduction of permanganate at another bare gold electrode. This novel flow-injection irreversible biamperometric method of determination ferulic acid can run without the application of an external potential. In the 0. 05 mol/L sulfuric acid, the oxidative peak current increases linearly with the concentration of ferulic acid in the range of 5 x 10 (-7) -8 x 10 (-5) mol/L, linear regression equation: i (nA) 4. 16 x 10(7) C + 50, and in the range of 1 x 10 (-4) - 1 x 10 (-3) mol/L, linear regression equation: i (nA) = 5. 6 x 10(6) C + 300 with a sampling frequency of 80 samples per hour. The detection limit for ferulic acid is 1. 2 x 10 (-7) mol/L and the RSD for 25 replicate determination of 2. 00 x 10 (-5) mol/L ferulic acid is 1. 2%. This proposed method has the advantage of wide linear range, high selectivity and sensitivity. The pertreatment procedure of the sample is simple, and it is suitable to online analysis. The method was applied to the analysis of sodium ferulate injection with satisfactory results.