Coulter counter

Coulter Counter is an electronic device that is widely used for counting and sizing particles suspended in electrolytes. It is named after Wallace H. Coulter, who developed the technology in the late 1940s. The Coulter principle has revolutionized the field of hematology and various other disciplines by providing a method for counting cells, bacteria, and other microscopic particles.

Principle

The Coulter Counter operates on the principle that when a particle suspended in a conductive liquid passes through a small aperture that also contains an electrolyte, it displaces its own volume of electrolyte. This displacement results in a change in electrical resistance across the aperture, which can be measured as a pulse. The number of pulses corresponds to the number of particles, and the amplitude of each pulse is proportional to the volume of the particle.

Components

The main components of a Coulter Counter include:

• An aperture tube that serves as the sensing zone.
• An electrode system to detect changes in electrical resistance.
• A counting and analysis system to process the signals.

Applications

Coulter Counters are extensively used in various fields including:

• Hematology for counting blood cells.
• Immunology for counting bacteria and viruses.
• Industrial applications for counting particles in suspensions, such as inks, paints, and emulsions.

Advantages

The Coulter Counter offers several advantages over traditional counting methods:

• High accuracy and reproducibility.
• Ability to count and size a wide range of particle sizes.
• Rapid analysis of large sample volumes.

Limitations

Despite its advantages, the Coulter Counter has some limitations:

• It requires particles to be suspended in an electrolyte solution.
• It cannot differentiate between live and dead cells without additional staining techniques.
• Particles of similar volume cannot be distinguished based solely on electrical impedance.

Recent Developments

Recent advancements in Coulter Counter technology include improvements in aperture materials and designs, as well as integration with computer systems for enhanced data analysis and storage capabilities.

See Also

• Flow Cytometry
• Microscopy
• Particle Size Analysis