In the lab, spectrophotometry is a measurement technique used in quantitative and qualitative analysis. This technique measures the intensity variation of an arbitrarily selected wavelength range of electromagnetic radiation. This optical measuring instrument allows high-precision measurement of the change in monochromatized light intensity.
Spectrophotometry is widely used in all field of natural science, and it is unthinkable to have a laboratory without at least one spectrophotometer, which was invented in 1940 by Arnold O Beckman.
The spectrophotometer is an optical measuring instrument that allows the measurement of the change in intensity of a single color passing through a sample from the ultraviolet range to the visible range to infrared.
The light source is distinguished according to the wavelength range of the analytical measurement using a monochromator. The already monochromatic beam of light enters the sample space of the instrument, where it passes through a cuvette placed in the light path. The light sensor measures the intensity of the light coming out of the cuvette and to convert it into an electrical signal, which can be in several ways, such as a photocell, photoelectron multiplier or, in more modern devices, a silicon cell.
In cheaper and simpler single-jet devices, only one cuvette can be placed at a time. The reference solution used is usually the solvent of the substance to be measured or analyzed. This solution can be considered as a solution in which the concentration of the solute is zero.
The apparatus must be zeroed for this concentration solution, where the light absorption is zero, its light transmittance is 100%, and then enters the light path.
Spectrophotometry has high accuracy and sensitivity speed. In addition, the spread of spectrophotometers has been helped by the fact that, while keeping the design of the instrument and the principle of measurement, it is possible to adapt the sample holding unit or integrate it into larger instrument unit.
The spectrophotometer measures the light absorption of a solution placed in a cuvette, but the cuvettes must also be capable of studying chemical reactions, i.e., chemical processes that continuous over time. Such as reaction may be the measurement of enzyme activity in biochemistry, clinical laboratory diagnostics, in which the enzyme substrate is transformed into a so-called product in the cuvette.
At the end of the 20th century, spectrophotometry was started to support PCR techniques to measure DNA or proteins. Finally, clinical laboratories that studied diseases have devices with automated robotic arms, automatic pipettes and centrifuges for the analysis of blood and urine samples that can perform extremely complex chemical tests based on spectrophotometry.
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Information compiled by Dezső Sándor.