Instrumentation:
The instrumentation for nepheloturbidometry is designed to measure the intensity of light scattered by particles in a sample.
The key components of a nephelometer include:
1. Light Source:
A monochromatic light source, typically a laser or LED, emits a beam of light that is directed through the sample. The choice of wavelength typically depends on the sample and the application.
2. Sample Chamber:
This is where the sample is placed. It's designed to ensure that the sample is illuminated uniformly and to minimize reflections and refractions.
3. Detectors:
Unlike traditional spectrophotometers, where the detector is placed directly opposite the light source, in nephelometers, the detector is positioned at an angle (usually 90°) to the incident light. This arrangement ensures that the detector measures scattered light, not transmitted light.
Some advanced nephelometers may have multiple detectors at various angles to capture scattered light at different orientations.
4. Monochromator or Filter:
This component is used to select a specific wavelength of light either before the light interacts with the sample (for the light source) or before it reaches the detector. In some instruments, especially those using lasers, this might not be necessary because the light source is already monochromatic.
5. Amplifier and Readout:
The weak signals from the detector are amplified to be read and processed. The readout will typically display the intensity of the scattered light, which can be related to the concentration of particles in the sample.
6. Microprocessor/Computer:
Modern nephelometers often include built-in microprocessors or are connected to computers for data handling, storage, and processing. This allows for more sophisticated analyses, calibration, and data interpretation.
7. Optical Components:
Lenses and mirrors are used to focus and direct the light beam appropriately through the sample and onto the detector.
8. Temperature Control:
In some sensitive applications, especially when studying biopolymers or macromolecules, the temperature can influence the measurement. In such cases, the nephelometer might have a temperature-controlled sample chamber.
When using a nephelometer, it's essential to calibrate the instrument using standards of known turbidity or scatter intensity.
These standards are often solutions with known concentrations of a scattering agent, like latex beads or formazin.
Applications:
1. Clinical Diagnostics:
One of the primary applications of nepheloturbidometry is in clinical diagnostics.
It is used for the determination of various components in serum like proteins, enzymes, lipids, and ions.
For instance, it can be used to measure serum levels of specific antibodies or antigens in immunological assays.
2. Water Quality Testing:
Nepheloturbidometry is used to determine the turbidity of water, which can be a measure of the water quality.
Turbidity can indicate the presence of microbes, algae, or other pollutants.
3. Pharmaceuticals:
It can be used to determine the size and concentration of particles in parenteral solutions or to monitor crystallization processes.
4. Food Industry:
Nepheloturbidometry can be used to assess the clarity of beverages or to measure the concentration of certain constituents in food products, such as pectin in fruit juices.
5. Research:
This technique is used in various research applications where there's a need to measure the concentration or size of particles in a solution, such as in nanoparticle research or in studying protein aggregation.
