Potentiometry

Potentiometric titrations are direct titrations based on principle acid-base titrations, redox reaction or precipitation titrations. The voltage across the substance in electrolyte solution is measured. The specific combination of electrodes, the neutral electrodes and reference electrodes are used to measure the voltage change. The test samples are dissolved in the proper solvent according to monograph, while the automatic electronic burette dispenses the certified titrant into the testing vessel. The millivoltage and dispense volume is recorded. The automatic potentiometric titration is used to perform USP/NF monograph assay and purity. Potentiometry is one of the methods of electroanalytical chemistry. It is usually employed to find the concentration of a solute in solution. In potentiometric measurements, the potential between two electrodes is measured using a high impedance voltmeter. Use of a high impedance voltmeter in important, because it ensures that current flow is negligible. Since there is no net current, there are no net electrochemical reactions, hence the system is in equilibrium. At its most fundamental level, a potentiometer consists of two electrodes inserted in two solutions connected by a salt bridge. The voltmeter is attached to the electrodes to measure the potential difference between them. One of the electrodes is a reference electrode, whose electrode potential is known. The other electrode is the test electrode. The test electrode is usually either a metal immersed in a solution of its own ions, whose concentration is to be discovered, or a carbon rod electrode sitting a solution which contains the ions of interest in two different oxidation states.