Voltammetry:
Redox reactions play a fundamental role in biochemistry and chemistry, thus it is useful to measure and tabulate the tendencies of various substances to gain or lose electrons. Standard electrode potentials, E° are measured relative to hydrogen, defined for a cell in which all activities are unity. The formal potential is the reduction potential that applies under specified conditions. For example, biochemists call the formal potential at pH 7 E°.
Whenever a proton appears in a redox reaction, reduction potentials are pH dependent.
Chronoamperometry, Cyclic Voltammetry and Differential Pulse Voltammetry are faradaic techniques used in these experiments. They differ with respect to applied wave form and resulting signal.
Chronoamperometry is a potential step method that has a square wave form. A potential is stepped from an initial value that causes no current to flow to a potential that causes current to flow. The resulting current is measured as it decreases over time. The signal follows the Cottrell equation. This equation can be used to calculate the surface area of an electrode or the concentration of analyte in solution.
Cyclic Voltammetry is a potential sweep method that has a triangular wave form. The potential is increased linearly with time to some specified potential value and then decreased over the same period of time back to the initial potential. The current at Ep can be calculated using the Randles-Sevcik equation.
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