Nepheloturbidometry is an instrumental method used for the quantitative analysis of substances in solution based on the measurement of the light-scattering properties of the solution.
Both nephelometry and turbidimetry assess the interaction of light with suspended particles, but nephelometry specifically measures the light scattered at an angle to the incident light, while turbidimetry measures the decrease in intensity of transmitted light due to scattering and absorption by the suspended particles.
Principle:
When a beam of light passes through a sample containing suspended particles (which are often larger than the wavelength of the incident light), these particles scatter the light in all directions.
The intensity of scattered light is measured at an angle (usually 90°) to the direction of the incident light.
This scattered light intensity is directly proportional to the concentration of the particles in the sample.
In nepheloturbidometry:
A light source emits a beam of light, which passes through the sample.
Suspended particles in the sample scatter this light.
A detector, placed at an angle to the incident light (commonly 90°), measures the intensity of the scattered light.
The intensity of the scattered light is compared with standards of known concentrations to determine the concentration of suspended particles in the unknown sample.
This method is particularly useful for measuring the concentration of macromolecules, such as proteins in solution, or the turbidity in water samples.