Introduction of five basic structures of ultraviolet-visible spectrophotometer

    Ultraviolet-visible spectrophotometer is a common analytical instrument in analysis and testing laboratory, which is used to measure the absorbance of the tested substance under certain wavelength irradiation, so as to realize qualitative or quantitative analysis of the substance. Its basic structure consists of light source, monochromator, absorption cell, detector and signal display system.

    I. Light source

    The light source is a device that provides incident light that meets the requirements. The light source commonly used in the visible region of the ultraviolet-visible spectrophotometer is a tungsten lamp, and the light source commonly used in the ultraviolet region is a hydrogen lamp or a deuterium lamp.

    1. Tungsten lamp

    Tungsten lamp is a common visible light source, which can emit a continuous spectrum with a wavelength of 325~2500nm, and the most suitable wavelength range is 320~1000nm, so it can also be used as a near infrared light source. When the tungsten lamp is heated to incandescent by electric energy, the distribution of light intensity in each band changes with the filament temperature. The temperature of the filament depends on the power supply voltage. Small fluctuation of power supply voltage will cause great change of tungsten light intensity. Therefore, it is necessary to use a regulated power supply. The working voltage of the tungsten lamp is 12V, and it can also be powered by a 12V DC power supply. The life of tungsten lamps can generally reach more than 10000 hours.

    At present, many photometers use halogen tungsten lamps instead of tungsten lamps, such as 7230 and 754 spectrophotometers. Tungsten halogen lamp has high luminous efficiency and long service life.

    2. deuterium lamp

    Deuterium lamp is a common ultraviolet light source. The wavelength range of light emitted by it is 190~400nm, and the wavelength range is generally 190~360nm. In order to ensure the stability of luminous intensity, a regulated power supply should also be used for power supply. The service life of deuterium lamps: domestic ones are generally 500~800 hours, imported ones are generally 1000 hours, and a few can reach 2000 hours.

    In recent years, lasers with high intensity and high monochromaticity have been developed and used as ultraviolet light sources. Commercially available laser sources include argon ion laser and tunable dye laser.