The basic analysis method of the online analyzer for organic compounds using spectroscopy is mainly based on the interaction between substances and light. The analysis is carried out by detecting the changes in spectral wavelength and intensity after the interaction. The following are some core methods:
absorption spectroscopy
Principle: When light passes through matter, if the energy of photons of a specific wavelength is exactly equal to the difference between the internal energy levels (such as electrons, vibrations, and rotational energy levels) of the material molecules or atoms, these photons will be absorbed by the matter, and then the intensity will decrease at the corresponding wavelength position in the transmitted light, forming an absorption peak. This process is like material "screening" photons of specific energy.
Representative technology:
UV Vis Absorption Spectroscopy: mainly measures the absorption of electronic transitions in molecules. In the field of analytical chemistry, it is commonly used to quantitatively analyze the concentration of substances by measuring the absorbance at specific wavelengths and determining the substance content based on Lambert Beer's law. The online analyzer for organic matter using spectroscopy often uses a 254nm spectral absorption coefficient SAC254 to measure the soluble organic matter content in reaction water, which can be converted into COD/BOD values under certain conditions.
Infrared absorption spectroscopy: Focusing on measuring the absorption of vibrational and rotational energy level transitions of chemical bonds in molecules, it is one of the key tools for identifying functional groups of organic compounds and analyzing molecular structures.
Atomic Absorption Spectroscopy (AAS): Based on the selective absorption of specific wavelengths of light by gaseous ground state atoms, it performs well in trace metal element analysis with high sensitivity and selectivity.
Emission spectroscopy method
Principle: After absorbing energy (such as light, heat, electricity, chemical energy, etc.), matter will be excited to a high-energy state (excited state). When the excited state particles return to a lower energy state or ground state, they will release energy in the form of light, producing emission peaks of specific wavelengths.
Application: Qualitative and quantitative analysis is carried out by measuring the wavelength and intensity of the emission spectrum of a substance. For example, Atomic Emission Spectroscopy (AES) is a method of analyzing the characteristic spectra emitted by atoms when they return to the ground state from an excited state.
Other related methods
Raman spectroscopy: When monochromatic light with a frequency of n0 is irradiated onto a transparent substance, the substance molecules will undergo scattering phenomenon. If this scattering is caused by energy exchange between photons and matter molecules, that is, not only does the direction of photon motion change, but its energy also changes, it is called Raman scattering. The frequency (μ m) of this scattered light is different from the frequency of the incident light, which is called Raman shift. The magnitude of Raman shift is related to the energy levels of molecular vibration and rotation. The method of studying material structure using Raman shift is called Raman spectroscopy.
NMR spectroscopy: Atomic nuclei absorb radio frequency radiation at specific frequencies (belonging to the microwave/radio frequency band) in a magnetic field, providing core technical support for molecular structure analysis.