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Structural analysis of UV-visible spectrophotometer
Ultraviolet spectrophotometry is an effective method to scientifically study the composition, structure, and interactions of substances based on their absorption spectra. The absorption spectrum of a substance is the result of molecules and atoms in the substance absorbing some specific wavelengths of light energy in incident light, and correspondingly the molecular vibrational level transition and the electronic energy level transition. Since various substances have different molecules, atoms and different molecular space structures, their absorption of light energy will not be the same. Therefore, each substance has its own unique and fixed absorption spectrum curve, which can be based on the absorption The level of absorbance at certain characteristic wavelengths on the spectrum discriminates or determines the content of the substance.
Generally, a UV-visible spectrophotometer is mainly composed of a light source system, a monochromator system, a sample chamber, and a detection system. The composite light emitted by the light source is decomposed into monochromatic light by the monochromator. When the monochromatic light passes through the sample chamber, part of it is absorbed by the sample, and the remaining unabsorbed light reaches the detector and is converted into an electrical signal. After magnification and data processing, the measurement results are given through the display system.
Light source: emits a continuous spectrum in the required wavelength range, has sufficient light intensity and is stable. Visible light region: tungsten lamp, iodine tungsten lamp (320 ～ 2500nm) ultraviolet region: hydrogen lamp, deuterium lamp (180 ～ 375nm); xenon lamp: ultraviolet and visible light regions can be used as light source.
Monochromator: A device that decomposes the continuous spectrum emitted by a light source into monochromatic light.
Grating: A large number of equally-spaced and equally-spaced streaks (600, 1200, 2400 / mm) are carved on the surface of the aluminized glass. Diffraction and interference occur when light passes through the grating to split the light.
Prism: The refractive index is different when light of different wavelengths passes through the prism.
Detector: The photoelectric effect is used to convert light energy into a current signal. Photocell, photocell, photomultiplier tube.
Galvanometer (indicator): scale display or digital display, automatic scanning record.
Absorption cell: used to hold the test and reference solution. Visible light region: optical glass cell; ultraviolet region: quartz cell.