Nephelometry is a laboratory technique used to measure the concentration of particles suspended in a liquid, particularly in the field of clinical chemistry and immunology. It is based on the principle of light scattering by particles in a sample, and it provides quantitative information about the amount and size distribution of the particles.
In nephelometry, a light source, typically a laser or a high-intensity lamp, is directed towards the sample containing the suspended particles.
The scattered light is then measured at a specific angle usually 90 degree using a detector. The intensity of the scattered light is directly proportional to the concentration of the particles present in the sample. This relationship allows nephelometry to provide quantitative measurements of particle concentrations which can be expressed mathematically using Beer-Lambert’s law. The law states that the intensity of light scattered by particles is directly proportional to their concentration.
Principle of Nephelometry
Nephelometry is based on the principle of measuring the scattered light by particles suspended in a liquid sample. A light source is directed towards the sample, and the intensity of the scattered light is measured at a specific angle using a detector. The amount of scattered light is proportional to the concentration of particles in the sample. By analyzing the scattered light, nephelometry provides quantitative measurements of particle concentrations.
A typical nephelometer consists of the following components:
- Light source: The light source in a nephelometer is typically a tungsten lamp or a laser. The light source emits a beam of light that passes through the sample chamber.
- Collimator: The collimator is a device that collimates the light beam, which means that it makes the beam of light parallel. This ensures that the light beam is evenly distributed across the sample chamber.
- Monochromator: The monochromator is a device that selects a specific wavelength of light from the light source. This is important because the amount of light scattered by a particle is dependent on the wavelength of light.
- Sample chamber: The sample chamber is the part of the nephelometer that contains the sample. The sample chamber is typically made of glass or quartz.
- Stray light trap: The stray light trap is a device that prevents stray light from reaching the detector. Stray light is light that is not scattered by the sample but that is reflected or refracted by the sample chamber or other components of the nephelometer.
- Photodetector: The photodetector is a device that measures the amount of light scattered by the sample. The photodetector is typically a photomultiplier tube. light intensity is converted into electrical signal by detector.
Applications of Nephelometry in Clinical biochemistry:
Used to perform various tests and assays in the field of clinical chemistry and immunology. Some of the common tests conducted using nephelometry include:
- Immunoglobulin Measurement: Nephelometry is widely used to measure the concentration of different immunoglobulins (IgG, IgM, IgA, etc.) in blood serum. This test is important in diagnosing and monitoring immune-related disorders such as autoimmune diseases and primary immunodeficiencies.
- Complement Component Analysis: Nephelometry is employed to measure the levels of complement components, such as C3 and C4, which are involved in the immune response. Abnormal complement levels can indicate certain autoimmune disorders or complement deficiencies.
- Rheumatoid Factor (RF) Test: Nephelometry is used to detect and quantify rheumatoid factor, an antibody commonly found in patients with rheumatoid arthritis. The test helps in diagnosing and monitoring the disease.
- C-Reactive Protein (CRP) Assay: Nephelometry is utilized to measure CRP levels in the blood, which is an acute-phase protein produced in response to inflammation. Elevated CRP levels can indicate the presence of infections, inflammatory conditions, or cardiovascular disease.
- Antinuclear Antibody (ANA) Test: Nephelometry is employed in the detection and quantification of antinuclear antibodies, which are associated with autoimmune disorders such as systemic lupus erythematosus (SLE). The ANA test helps in diagnosing and monitoring these conditions.
- Specific Antibody/Antigen Assays: Nephelometry is used in various specific antibody or antigen assays, such as the measurement of specific viral or bacterial antigens, antibodies against specific pathogens, or specific biomarkers associated with certain diseases.
The technique is highly versatile and can be applied to measure a wide range of analytes, including proteins, antibodies, antigens, and other macromolecules. The specific tests conducted depend on the clinical or research needs and the biomarkers of interest.
Limitations of nephelometry :
- Interference from other substances: Nephelometry can be affected by the presence of other substances in the sample, such as proteins, lipids. These substances can scatter light and interfere with the measurement of the concentration of the particles of interest.
- Requirement for specific wavelength: The amount of light scattered by a particle is dependent on the wavelength of light. This means that nephelometry must be performed at a specific wavelength that is appropriate for the particles of interest.
- Limited sensitivity: Nephelometry is not as sensitive as some other techniques for measuring the concentration of particles. This means that it may not be possible to measure the concentration of particles in very dilute solutions.
- Nephelometry can be affected by the refractive index of the sample.
In summary, nephelometry is a valuable technique used in clinical chemistry and immunology to measure the concentration of particles suspended in a liquid sample. It utilizes the principle of light scattering to provide quantitative measurements, making it a versatile and reliable tool in laboratory analysis.
| Feature | Turbidimetry | Nephelometry |
|---|---|---|
| Principle | Measures the amount of light that is transmitted through a sample | Measures the amount of light that is scattered by a sample |
| Detector | Photometer | Nephelometer |
| Angle of measurement | None | 90 degrees |
| cuvette | Rectangular cuvette used | Semioctagonal cuvette used |
| Sensitivity | Lower | Higher |
| Specificity | Lower | Higher |
| Applications | Determination of protein concentration, turbidity of liquids, and particle size | Immunoassays, determination of antigen-antibody complexes, and |