Why to use the UV spectrum analysis to detect the water quality?
Although water resources are abundant, the concept of water quality is taken as the evaluation criterion, and now the quality problem of urban water supply system and rural domestic production water is extremely urgent to decline. In the water quality monitoring, the water quality monitoring technology based on ultraviolet spectrum analysis is an important development direction in the modern environmental monitoring work, and the water quality monitoring technology based on ultraviolet spectrum analysis has significant advantages of real-time detection, strong pertinence, high accuracy and low cost.
At present, the world is facing a very serious problem of water pollution, water quality monitoring has become one of the key contents of modern environmental management. Though water monitoring, quality and pollution environment can be accurately, comprehensively and timely reflected. Water quality monitoring techniques are mainly chromatographic separation technology, atomic spectroscopy, chemical analysis and electrochemical analysis. Including molecular spectrosopy analysis technique is the most widely used in water quality monitoring technology, based on the UV spectrum analysis in drinking water, surface water and water quality monitoring in industrial wastewater has significant advantages, become an important development direction of water quality monitoring technology.
UV-Vis absorption spectra are collectively called electron spectra. The absorption spectrum generated by molecules that can absorb electromagnetic waves of 200-800nm in the UV-Vos regoin is called UV-Vis absorption spectrum, or UV-spectrim in short. Ultraviolet visible light can be divided into three regions: the far ultraviolet region of 10-190nm; uv region 190-400nm; the visible area is 400-800nm.
The far UV region of 10-190nm is also known as the vacuum ultraviolet region. Oxygen, nitrogenm, water, and carbon dioxide strongly absorb UV light in this region. General ultraviolet spectrometers can detect uv light (200-400), so uitraviolet spectrun is also called UV-Vis spectrum. UV and IR spectra are collectively called molecular spectra. Both belong to the absorption spectrum. UV spectrum is caused by the electron transition from the groud state to the exicited state when the sample molecule absorbs certain wavelength of light. Ultraviolet spectrum spectrum is also called electron absorption spectrum.
Molecules are usually in the ground state, but when molecules by ultraviolet radiation, cna absorb the energy of a given size (Δ E = h ν) of uv light, the energy equals the ground state with a high energy electron difference (E1 -E0); make the electronic from E0 transition to E1. The uv spectrum was obtained by recording the changes of uv light intensity before and after the absorption spectral.
Principle of molecular absorption spectroscopy. When the radiation energy from the external conduction is applied to the molecules of the material to be detected, the internal material will be absorbed or released in the form of electromagnetic radiation. When the radiation energy is applied to the transparent or translucent substance to be detected, the substance will absorb the radiation energy corresponding to the frequency of its motion state change and migrate to the higher solar energy, the spectrum produced by the selective absorption of this substance to radiation is called the absorption spectrum. The UV-Vis spectrum is one of these absorption spectra. And the other important characteristic of it is that the spectrum produced by its electron transition is a wide band.
When a molecule is subjected to continuous light irradition of a certain range of wavelengths, the energy of its photon will be transferred to the molecule and be selectively absorbed by the molecule, reducing the intensity of light energy in this region. Therefore, the transmitted light spectrum composed of absorption spectral lines is the molecular absorption spectrum.
The core of UV spectral water quality detection technology is to detect the absorotion rate of ultraviolet light in a substance to determine its concentration. The absorption law based on it is Lambert-Beer law. I0 is the intensity of monochromatic light emitted in the initial state, and I is the intensity of monochromatic light output after being absorbed by some measured substance C. According to the proportional relationship between the intensity of I and the concentration of C, the change value of light intensity before and after input and output can be converted into the concentration information.
Overall Framework For System Design:
UV spectral water quality detection technology is mainly composed of hardware and software, of which the hardware part is composed of optical path system (UV light source and spectroscopic system), sample pool, signal acquisition and other parts. In the use of light absorption rate for water quality testing work path as: receives uv light source through spectroscopic system is decomposed into different spectra, different materials of measurement will automatically choose the corresponding spectrum, after water sample pool some is absorbed and all samples, the other part is converted to electrical signals, this part will be software design for data transmission to the central processing chip, in order to set the ultraviolet spectrum of algorithm calculates the testing material content, finally on the electronic screen for display.
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