Nephelometry

Nephelometry

Nephelometry is a technique used in the field of clinical chemistry and immunology to measure the concentration of suspended particles in a liquid by analyzing the light scattered by the particles. This method is particularly useful for quantifying proteins and other macromolecules in biological samples.

Principle of Nephelometry

Nephelometry is based on the principle of light scattering. When a beam of light passes through a sample containing suspended particles, the particles scatter the light in different directions. The intensity of the scattered light is proportional to the concentration of the particles in the sample. By measuring the intensity of the scattered light at a specific angle, the concentration of the particles can be determined.

The technique is sensitive to the size and shape of the particles, as well as the wavelength of the incident light. Typically, nephelometers are designed to measure scattered light at an angle of 90 degrees to the incident light, although other angles can also be used depending on the specific application.

Applications of Nephelometry

Nephelometry is widely used in clinical laboratories for the quantification of various analytes, including:

• Proteins: Nephelometry is commonly used to measure the concentration of proteins such as immunoglobulins, albumin, and fibrinogen in serum or plasma.
• Turbidity: It is used to assess the turbidity of solutions, which can be an indicator of bacterial growth or the presence of particulate matter.
• Antigen-Antibody Reactions: Nephelometry is employed to quantify antigen-antibody complexes in immunoassays, providing valuable information for diagnosing and monitoring diseases.

Types of Nephelometry

There are two main types of nephelometry:

• End-point Nephelometry: This method measures the scattered light at a fixed time point after the reaction has reached equilibrium. It is suitable for reactions that proceed to completion.
• Kinetic Nephelometry: This method involves continuous monitoring of the scattered light over time, allowing for the analysis of reaction kinetics. It is useful for reactions that do not reach a stable end-point.

Advantages and Limitations

Advantages

• Sensitivity: Nephelometry is highly sensitive and can detect low concentrations of analytes.
• Speed: The technique provides rapid results, making it suitable for high-throughput testing.
• Non-destructive: The sample is not consumed during the measurement, allowing for further analysis if needed.

Limitations

• Interference: The presence of other particles or substances in the sample can interfere with the measurement.
• Calibration: Accurate calibration is essential for reliable results, requiring the use of standards.
• Particle Size Dependency: The technique is sensitive to the size and shape of the particles, which can affect the accuracy of the measurement.

Also see

• Turbidimetry
• Spectrophotometry
• Immunoassay
• Light scattering