2022-03-24
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What is a spectrophotometer?
The basic principle of the spectrophotometer is that the substances in the solution have an absorption effect on light under the excitation of light. The absorption of light by substances is selective, and various substances have their own absorption spectra. Therefore, When a monochromatic light passes through the solution, its energy will be absorbed and weakened, and the degree of light energy weakening has a certain proportional relationship with the concentration of the substance, that is, it conforms to the Lambert-Beer law.
Mainly divided into visible spectrophotometer and UV-visible spectrophotometer.
(1) Visible spectrophotometer
An instrument used to measure the absorbance of the substance to be tested to visible light (400-760nm) and perform quantitative analysis, called a visible spectrophotometer.
(2) UV-Vis spectrophotometer
Ultraviolet-visible spectrometer is an instrument used to measure the absorbance of the substance to be tested to visible light or ultraviolet light (200-760nm) and perform quantitative analysis. It can measure the concentration of nucleic acid and protein, as well as the density of bacterial cells. The UV spectrophotometer can be divided into single beam, false double beam and double beam. Their uses are different.
Single beam: It is suitable for measuring absorbance or transmittance at a given wavelength. Generally, full-band spectral scanning cannot be performed, and the light source and detector are required to have high stability.
Double beam: automatic recording, fast full-band scanning. It can eliminate the influence of factors such as unstable light source and detector sensitivity change, and is especially suitable for structural analysis. The equipment is complicated and expensive.
Pseudo double beam is also proportional double beam. Its principle is that the light emitted by the same monochromator is divided into two beams, one beam directly reaches the detector, and the other beam reaches the other detector after passing through the sample.
The advantage of this kind of instrument is that it can monitor the error caused by the change of the light source, but it cannot eliminate the influence caused by the reference.
Spectrophotometer Notes?
(1) The spectrophotometer should be placed in a dry room, and placed on a firm and stable workbench during use, and the indoor lighting should not be too strong. In hot weather, do not use a fan to blow air directly to the instrument to prevent the bulb filament from shining and unstable.
(2) Before using the spectrophotometer, the user should first understand the structure and working principle of the instrument, as well as the function of each control knob. Before pressing the power supply, the safety performance of the instrument should be checked. The power supply wiring should be firm, and the power supply should be good. The starting position of each adjustment knob should be correct, and then press the power switch.
(3) When the spectrophotometer is not connected to the power supply, the meter pointer must be on the "0" scale line. If this is not the case, the calibration screw on the meter can be used to adjust.
How to choose a spectrophotometer?
①Visible type: 721\722\722N\722S, 7230G\723N\723S, V729
②UV-visible type: UV752/UV752N, UV754PC, UV755B, UV756/UV756CRT, UV759/UV759CRT, UV1810\UV1810S, UV762, UV1900, UV1901\UV1901PCS