The turbidimetry is an analytical measurement technique determines how a light beam is attenuated it moves through a suspension. This attenuation occurs thanks to the absorption and scattering phenomena that light experiences due to the particles.
Then, the dimensions of the particles present in a suspension can be deduced by measuring the turbidity in it. In this sense, this procedure is used to quantify the absorption and scattering of light: its dependence on the dimensions of the particles and their concentration in the suspension is demonstrated.
Likewise, analytical methods based on turbidimetry have certain advantages, such as: short analysis times, experimental simplicity, reduced costs (relative to other processes), no damage to the sample and elimination of the need for calibration.
What does it consist of?
Turbidimetry is based on the measurement of the intensity of light radiation that is transmitted through a medium made up of particles that show a certain dispersion, which have a different refractive index than the suspension where they are.
As previously described, there is an attenuation of the light intensity due to the scattering phenomenon, for which the light radiation that does not undergo this scattering is studied.
This technique consists of making the light pass through a filter, by means of which radiation is produced whose wavelength is known; later, this radiation passes through a cuvette in which a solution is found and is collected by a cell of a photoelectric nature. This gives a quantification of the light that has been absorbed.
In other words, this technique is used to quantify the turbidity that a solution has, based on measuring the effects that this property exerts on the scattering and transmission of light radiation.
It should be noted that for these analyzes it is essential that the suspension is uniform, since the lack of uniformity can affect the measurement results.
Turbidity
It can be said that the turbidity of a fluid is due to the presence of particles that are finely divided in suspension; Therefore, when making a beam of light pass through a sample that has a certain turbidity, its intensity decreases due to scattering.
Also, the amount of light radiation that has been scattered is dependent on the distribution of the dimensions of the particles and their concentration, and is measured through a device called a turbidimeter.
As in turbidimetric measurements the intensity of the light radiation that is transmitted through the sample is determined, the more dispersion there is, the lower the intensity of the transmitted light.
Thus, when transmission estimates are made, such as absorption estimates, the decrease in light intensity depends on the concentration of the species found in the cell with some scattering, without variations in wavelength..
When the theory of light scattering is used, turbidity measurements are obtained and the dimensions of the particles are determined, as well as their distribution in the suspension.
Turbidimeter
The instrument used to measure the relative clarity of a fluid is known as a turbidimeter, by quantifying light radiation in a fluid sample that has undergone scattering caused by suspended particles.
These suspended particles make it difficult for radiation to be transmitted through fluids, hindering its passage. Then, the turbidity of a substance could originate due to a single species or a set of chemical species.
Turbidimeters measure this obstruction, in order to estimate the turbidity or intensity of the light radiation present in the sample, the nephelometric turbidity units with which it is represented are known as NTU. However, these instruments are not used to estimate particle dimensions.
The structure of turbidimeters is made up of a source of light radiation, a lens that allows a light beam to be focused and guided through a fluid and a photoelectric device in charge of detecting and estimating the amount of light radiation that has been scattered..
In addition, there is a kind of trap that prevents the detection of other light radiation that may interfere with the measurement.
Applications
This measurement technique has a large number of applications, among which the detection of contaminants in the form of traces in a variety of samples and the estimation of the dimensions of the particles in various fluids stand out.
Furthermore, turbidimetry is used in the field of biology to quantify the cells present in certain solutions, and in the observation of microbiological cultures for the manufacture of antibiotic drugs.
In the area of chemistry that studies clinical diagnosis, the immunoturbidimetry method is used to estimate serum-type protein structures that cannot be detected by other clinical techniques.
On the other hand, turbidimetry is used in water quality control to estimate the quantity of suspended particles in waters of natural origin, as well as in the water of the processing streams.
In the same way, this analytical method is used to estimate the amount of sulfur present in samples of oil, coal and other substances of an organic nature; in this case, there is a precipitation of sulfur in the form of barium sulfate.
References
- Khopkar, SM (2004). Basic Concepts of Analytical Chemistry. Recovered from books.google.co.ve
- Wikipedia. (sf). Turbidimetry. Recovered from en.wikipedia.org
- Britannica, E. (nd). Chemical Analysis. Retrieved from britannica.com
- Visual Encyclopedia of Chemical Engineering. (sf). Turbidimeters. Obtained from encyclopedia.che.engin.umich.edu
- Kourti, T. (2006). Encyclopedia of Analytical Chemistry: Applications, Theory and Instrumentation. Recovered from onlinelibrary.wiley.com