Discuss the spectrum distribution range of ultraviolet-visible spectrophotometer

Release time：2019-03-19

Ultraviolet-visible spectrophotometer uses a light source that can generate multiple wavelengths through a series of spectroscopic devices, thus generating a specific wavelength of light source. After the light source passes through the tested sample, part of the light source is absorbed, and the absorbance value of the sample is calculated, thus converting it into the concentration of the sample. The absorbance of the sample is proportional to the concentration of the sample.



Spectrum distribution range of ultraviolet-visible spectrophotometer:



Different light sources have their own emission spectra, so different light sources can be used as light sources for the instrument.



Emission spectrum of tungsten lamp: The spectrum of 400-760 nm wavelength emitted by tungsten lamp source. After refraction through a prism, a continuous chromatogram composed of red, orange, yellow, green, blue, indigo and violet can be obtained. The chromatogram can be used as a light source of visible spectrophotometer.



Emission spectrum of hydrogen lamp (or deuterium lamp): Hydrogen lamp can emit 185-400 nm wavelength spectrum, and can be used as the light source of ultraviolet photometer.



Absorption spectra of substances



(1) If a solution of a substance is placed between the light source and the prism, then the spectrum displayed on the screen is no longer the spectrum of the light source. It has several dark lines, that is, the light of some wavelengths in the emission spectrum of the light source disappears due to the absorption of the solution. The absorption spectrum of the solution is called the absorption spectrum of the solution. The absorption spectrum of different substances is different. Therefore, according to the absorption spectrum, it can be used. Identification of substances in solution. Absorption spectra of substances.



(2) When light passes through a solution of a substance, the intensity of the transmitted light decreases. Because part of the light is reflected or dispersed on the surface of the solution, part of the light is absorbed by the substance that makes up the solution, and only part of the light can pass through the solution. Incident light = reflected dispersed light absorbs light through the solution. If we use distilled water (or solvent that makes up the solution) as a "blank" to correct reflection, dispersion. The loss of incident light caused by such factors as incident light = absorbed light 10 through light.