A double-beam UV-Vis spectrophotometer (hereafter referred to as an instrument) is a device in which the monochromatic light emitted by the monochromator is split into two beam structures of sample and reference by a beam switch (chopper). ). Instrument.
It can eliminate the influence of light source instability and amplifier gain fluctuations, and automatically record and scan the absorption spectrum of the substance.
Normally the device performs some self-tests after start-up, but it should still be calibrated according to this regulation. The wavelength range of the instrument is 195-800 nm and the slit is adjustable from 0.1-5 nm.
Principle of operation
UV-visible spectrophotometry is an instrumental analysis that utilizes the absorption of radiation in the ultraviolet-visible spectral range by material molecules.
ThisMolecular absorption spectrum is generated by the transition of valence electron energy level and is widely used in qualitative and quantitative analysis of inorganic and organic substances.
The Lambert-Beer law (Lambet-Beer) is the fundamental law of light absorption, commonly known as the law of light absorption, and is the basis and basis for quantitative analysis by spectrophotometry.
If the wavelength of the incident light is constant, the absorption of the solution is a function of the concentration c of the light-absorbing substance and the thickness of the absorbing medium (absorption path).
The usual expression is as follows (where ε is a coefficient):
A=ε c l
Ultraviolet-visible spectrophotometer is a conventional analytical instrument based on the principle of ultraviolet-visible spectrophotometry. Depending on the design of the beam path, UV-Vis spectrophotometer can be divided into single-beam spectrophotometer, double-beam spectrophotometer and dual-wavelength spectrophotometer.
Basis for Formulation
This procedure relates primarily to the National Metrology Verification Regulations “JJG178-2007 Ultraviolet, Visible, and Near-infrared Spectrophotometers ', 'JJF1641 - The Outline for Type Evaluation of UV-Vis Spectrophotometers 2017 and the 2015 Edition of the Four Guidance General Rules 0401 UV-Vis Spectrophotometry of the Chinese Pharmacopoeia have been prepared.
Elements and technical requirements
Wavelength accuracy ≤±1.0 nm (ultraviolet range), ≤±2.0 nm (near 500 nm);
Wavelength repeatability ≤0.5 nm.
Baseline straightness ≤ 0.01 absorbance.
0% line noise ≤ 0.1%, 100% line noise ≤ 0.5%.
The absorption accuracy should meet the requirements.
Spectral bandwidth ≤ marked bandwidth ± 20%.
Absorption Cell Agreement Error ≤0.5%.
Test result processing
If all self-test results meet the technical requirements, it is qualified and can be used. If the test result does not meet the requirements, the device should be reset and then subjected to a self-test. It can only be used if it complies with the regulations.