The key difference between potentiometry and amperometry is that potentiometry measures the electric potential while maintaining a constant electric current between the two electrodes, whereas amperometry monitors electric current while keeping the potential constant.
Potentiometry and amperometry are important analytical techniques in analytical chemistry. Potentiometry is a method of electroanalysis used to find the concentration of a solute in a solution. Amperometry is the technique to detect the ions in a solution depending on electric current or changes in electric current.
CONTENTS
1. Overview and Key Difference
2. What is Potentiometry
3. What is Amperometry
4. Potentiometry vs Amperometry in Tabular Form
5. Summary – Potentiometry vs Amperometry
What is Potentiometry?
Potentiometry is a method of electroanalysis usually used to find the concentration of a solute in a solution. In other words, we measure the potential of an electrochemical cell under static conditions during potentiometry. This is because no or negligible current flows through the electrochemical cell when its composition remains unchanged. Therefore, potentiometry is very useful as a quantitative method.
Initially, potentiometry was restricted to redox equilibria at metallic electrodes, which tends to limit its application to a few ions. Later, scientists discovered that the potential difference across a thin glass membrane could be given as a function of pH when opposite sides of the membrane are in contact with solutions that consist of different hydronium ion concentrations.
A potentiometric electrochemical cell consists of two half-cells. Each half cell contains an electrode that is immersed in a solution of ions where the activity of the ions determines the potential of the electrode. Moreover, we can use a salt bridge consisting of an inert electrolyte such as potassium chloride to connect two half cells.
What is Amperometry?
Amperometry is the technique of detection of ions in a solution depending on electric current or charges in electric current. This technique is useful in electrophysiology when studying vesicle release events with the use of a carbon fiber electrode. In contrast to patch-clamp techniques, we do not insert the electrode used for amperometry into the cell. However, we have to take it to close proximity of the cell. Thereafter, we can get the measurement from the electrode through an oxidizing reaction of a vesicle cargo that is released into the medium. Alternatively, we can use capacitive measurements.
There are two major detection methods of amperometry: single potential amperometry and pulsed amperometry. In single potential amperometry, we use an analyte that can undergo oxidation or reduction as a candidate for amperometric detection. In pulse amperometry, we use it for analytes that tend to foul electrodes.
What is the Difference Between Potentiometry and Amperometry?
Potentiometry is a method of electroanalysis usually used to find the concentration of a solute in a solution. Amperometry is the technique of detection of ions in a solution depending on electric current or charges in electric current. The key difference between potentiometry and amperometry is that potentiometry measures the electric potential while maintaining a constant electric current between the two electrodes, whereas amperometry monitors electric current while keeping the potential constant.
Moreover, potentiometry is used in clinical chemistry for analysis of metals, analysis of cyanides, ammonia, etc. in wastewater, in agriculture for detection of different elements in soil, etc. Amperometry, on the other hand, is used in oxygen monitors or oxygen cathodes, titrations such as redox, precipitation and complexometric titrations, etc.
The following table summarizes the difference between potentiometry and amperometry.
Summary – Potentiometry vs Amperometry
Potentiometry and amperometry are important analytical techniques in analytical chemistry. The key difference between potentiometry and amperometry is that potentiometry measures the electric potential while maintaining a constant electric current between the two electrodes, whereas amperometry monitors electric current while keeping the potential constant.
Reference:
1. “Amperometry.” An Overview | ScienceDirect Topics.
2. “Definition of Potentiometry” Chemicool Dictionary.
Image Courtesy:
1. “Raster tunnel potentiometrie” By Basdu – Own work (CC BY-SA 3.0) via Commons Wikimedia