Chapter 8 - Chronoamperometric determination of ascorbic acid on paper-based devices

Abstract

Electroanalysis comprises many different techniques. One of the simplest is chronoamperometry, a potential step technique, where the potential moves forward from an initial to a final value (single step technique), but that can also move back (to the initial or other potential value) in the double potential step technique. Then, the intensity of the current (“amperometry”) is recorded with time (“chrono”), with an i-t curve being the response signal (chronoamperogram). The analytical signal is an instantaneous current measured at a fixed time. As the current contains two components, faradaic and nonfaradaic, and the latter one decays faster, the current is usually measured some seconds after the potential step. In this experiment, a single-step chronoamperometry is employed for the determination of ascorbic acid in fruit juices. A cyclic voltammogram is first recorded to select the values of the initial and final potentials. A low-cost paper-based electrochemical cell is employed to fit with the simplicity of the technique.