Determination of ferulic acid in Chinese proprietary medicine based on a poly-glutamic acid film sensor

The poly-glutamic acid modified electrode has been prepared by direct electro-polymerization of D-glutamic acid on the surface of glassy carbon electrode. In pH 4.2, 0.1 mol L^?1 HAc-NaAc buffer solution, the film modified electrode exhibited remarkable enhancement effect to the electrochemical responses of ferulic acid. The action mechanism was preliminarily explored. In the range of 2.0 × 10^?7 to 1.0 × 10^?5 mol L^?1, and 1.0 × 10^?5 to 3.0 × 10^?4 mol L^?1, the oxidation peak current has a linear relationship to the concentration, and the detection limit was estimated to be 7.0 × 10^?8 mol L^?1. This method has been adopted to detect trace amount of ferulic acid in Chinese proprietary medicine, and the recovery was from 97.8 to 102.4%.