Complexometric titration
- S-1-PHARMACEUTICAL-ANALYSIS
- Feb 26
- 2 min read
Updated: Apr 7
Introduction:
Complexometric titration is a volumetric analysis technique used to determine the concentration of metal ions by forming a complex with a chelating agent (titrant).
It is commonly applied in fields such as chemistry, environmental science, and pharmaceutical analysis, particularly for quantifying metal ions, especially transition metals.
Principle:
The titration is based on the formation of stable complexes between metal ions and chelating agents.
Chelating agents, such as EDTA, have multiple donor atoms (e.g., oxygen, nitrogen) that form coordinate bonds with metal ions, creating complex ions.
Key Components:
1) Analyte:
The metal ion (or ions) whose concentration is being determined.
2) Titrant (Complexing Agent):
A chelating agent added in a known volume and concentration to form complexes with the metal ions.
Common agents include EDTA and DTPA.
3) Indicator:
Signals the endpoint, often through a color change.
Examples include Eriochrome Black T or Murexide, which change color when the metal ion forms a complex with the chelating agent.
Applications:
Determination of metal ion concentrations in environmental samples, such as water and soil.
Analysis of trace metal ions in pharmaceuticals.
Quality control in the production of food and beverages.
Monitoring of heavy metal pollution in industrial effluents.
Research in analytical chemistry and metallurgy.
Methods to detect the endpoint of titrations:
1) Visual Indicators:
Indicators like Eriochrome Black T change color when they form a complex with metal ions.
A second color change indicates the endpoint when all metal ions are complexed.
2) Potentiometric Detection:
Measures potential difference between electrodes.
The endpoint is marked by a sharp change in potential as all metal ions react with the chelating agent.
3) Conductometric Detection:
Monitors the electrical conductivity of the solution.
The endpoint is reached when conductivity changes significantly as metal complexes form.
4) pH-Metric Detection:
Tracks pH changes during titration.
A sudden pH shift indicates the endpoint when all metal ions are complexed.
PM Indicator in Complexometric Titration
The term PM indicator refers to the Patton-Reeder indicator, used in complexometric titrations.
It is not a category, but a specific indicator named after its developers, Patton and Reeder.
Common Indicators Used in Complexometric Titrations:
Eriochrome Black T (EBT)
Murexide (Ammonium Purpurate)
Calcon (1-hydroxy-3-(m-sulfonatophenylazo)-2-naphthoic acid)
Solochrome Dark Blue (SDB)
Xylenol Orange
These indicators are commonly employed for detecting endpoints in titrations involving metal ions.
