The two major classes of electrochemical methods are Potentiometric and Amperometric.
Electrochemical methods are powerful analytical techniques that utilize the relationship between chemical phenomena and electrical quantities. They measure properties like potential, current, or charge to gain insights into chemical systems, often focusing on reactions occurring at electrode surfaces.
Based on the electrical property measured or controlled, electrochemical methods can be broadly categorized. According to the provided reference, these methods are typically split into two major classes:
- Potentiometric
- Amperometric
Let's delve into each type briefly.
Potentiometry
Potentiometry involves measuring the potential difference (voltage) between two electrodes in an electrochemical cell under conditions of zero current. The reference states that in potentiometric methods, the potential responds to changes in the activity of the analyte species present in the solution in a well defined manner described by the Nernst equation.
- What is measured: Potential difference.
- Current condition: Zero or negligible current flow.
- Relationship: Potential is related to analyte concentration (activity) via the Nernst equation.
- Common uses: pH measurement, determination of ion concentrations using ion-selective electrodes.
Amperometry
Amperometry involves measuring the current flow in an electrochemical cell while keeping the potential between the electrodes constant. The current measured is proportional to the rate of the electrochemical reaction occurring at the working electrode, which in turn depends on the concentration of the analyte.
- What is measured: Current.
- Potential condition: Constant or controlled potential.
- Relationship: Current is related to the rate of reaction and thus analyte concentration.
- Common uses: Biosensors (e.g., glucose sensors), some types of titrations.
Summary Table
Here is a quick comparison of the two main types:
| Feature | Potentiometry | Amperometry |
|---|---|---|
| Measured | Potential (Voltage) | Current |
| Controlled | Current (Zero) | Potential |
| Key Principle | Potential related to analyte activity (Nernst Equation) | Current related to reaction rate/analyte concentration |
| Examples | pH meter, Ion-selective electrodes | Glucose sensors, Amperometric detectors in chromatography |
These two classes form the foundation for many specialized electrochemical techniques used in analytical chemistry, materials science, and various industrial applications.
