Bismuth Film Electrode as an Alternative for Mercury Electrodes: Determination of Azo Dyes and Application for Detection in Food Stuffs

Bismuth electrodes were investigated and exhibit electrochemical properties similar to mercury electrodes but with much lower toxicity. An electrochemical application of bismuth film modified glassy carbon electrode for azo dyes determination was investigated. The plating step was optimized in order to achieve its analytical efficiency. A plating potential of −0.9 V in a solution of 200 mg/L Bi(NO 3 ) 3 , 0.5 M HNO 3 for 100 s yields to a suitable electrode (in terms of stability and detection). Azo dyes such as azorubine (i.e., carmoisine, E122), amaranth (E123), ponceau 4R (i.e., new coccine, E124) and allura red (E129) were determined by differential pulse voltammetry in a NaCl solution in the concentration range of few ppm to 100 ppm. The reproducibility of the signal, characterized by the relative standard deviation, was found to be less than 5%, the detection and quantification limits were few mg/L. The influence of other food components on the signal was studied and the applicability was tested on real beverages samples.