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Spectrophotometry is a qualitative or quantitative analysis of the substance at a specific wavelength or within a certain wavelength range. 200-380nm is the ultraviolet region, and the instrument used is ultraviolet spectrophotometer. Spectrophotometer has become a conventional instrument in modern laboratory, which is often used to quantify nucleic acid, protein and bacterial growth concentration. The instrument is mainly composed of light source, monochromator, sample room, detector, signal processor and display and storage system.