The working principle and application object of spectrophotometer

1. Working principle of ultraviolet spectrophotometer:
The organic matter being analyzed (similar to the infrared spectrometer) is irradiated with a certain frequency of ultraviolet visible light, causing a transition of the valence electrons in the molecule, which will be selectively absorbed. UV-visible spectrometers cover a wavelength range of 0.2-0.8 microns (corresponding to a wave number of 50,000-12500 cm-1), which is widely used in organic chemistry research. It is commonly used as a material identification, purity check, and study of organic molecular structures.
2. What is a spectrophotometer?
A spectrophotometer is a measuring instrument that samples a reflective object or a transmissive object with a discontinuous wavelength. Because of the different structures of molecules of different objects, the absorption capacity of light of different wavelengths is also different. Therefore, each object has a specific absorption spectrum. An instrument that can separate each monochromatic light from a mixture of various wavelengths and measure its intensity is called a spectrophotometer.
Spectrophotometry is the development of colorimetry. The colorimetric method is limited to the visible light region, and the spectrophotometric law can be extended to the ultraviolet region and the infrared region. The spectrophotometric rule requires near-true monochromatic light with a spectral bandwidth of no more than 3-5 nm and a wavelength of less than 1 nm in the ultraviolet region, with high precision from prisms or gratings. A spectrophotometer is an instrument that quantitatively and qualitatively analyzes a substance by spectrophotometry. The spectrophotometer can be divided into an ultraviolet spectrophotometer, a visible spectrophotometer (or a colorimeter), an infrared spectrophotometer or an atomic absorption spectrophotometer.
3. What can the UV spectrophotometer be used to measure?
The spectrophotometer is a necessary inspection equipment for QS and HACCP certification for food factories and drinking water plants. Ultraviolet absorption spectroscopy is mainly used for quantitative analysis and purity analysis of known substances.
1) Determination of the content of the substance in the solution The absorbance of the standard solution (solution of known concentration) and the solution of unknown (concentration of the solution to be determined) are compared, since the thickness of the absorption cell used is the same. It is also possible to first measure the absorbance of different concentrations of the standard solution, and draw a standard curve. The standard curve should be a straight line within the selected concentration range, and then the absorbance of the unknown liquid is determined, and the corresponding curve can be found from the standard curve. concentration.
2) Identification of the compound by ultraviolet spectroscopy The monochromatic light of different wavelengths is passed through a solution of a certain concentration, and the absorbance of the solution for each monochromatic light is measured, and then the wavelength is the abscissa, and the absorbance is the vertical seat. The absorbance is plotted - the wavelength curve, which is the absorption spectrum curve. Various substances have their own absorption spectrum curves, so the absorption spectrum curve can be used to identify the species. The UV absorption spectrum is relatively simple, and the UV absorption spectrum of the same substance should be completely

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