Fig. 4.

Blocking agents can affect the amplitude of the signal generated by the working electrode. The current (y-axis on the left) generated by the graphite felt at −340 mV when BSA, carrageenan gum, nonfat milk, and Tween-20 were used as blocking agents was measured (dark gray bars). The absence of a blocking solution was also tested as a control. In addition, the optical density readings (red horizontal line) of the solutions were recorded (y-axis on the right). Measurements represent the average values of three independent experiments with error bars indicating the standard error of the mean