Spectrophotometers have become conventional instruments for modern molecular biology laboratories. Commonly used in nucleic acids, proteins. Quantitative and quantitative determination of bacterial growth concentration.
Spectrophotometer instrument composition: the instrument mainly by the light source, monochromator, sample room, detector, signal processor and display and storage systems.
Spectrophotometric method is the specific wavelength or a certain wavelength range of light absorption, the material qualitative or quantitative analysis. (2) a visible region of 380 to 780 nm, (3) 2.5 to 25 m (4000 cm & lt; -1 & gt; to 400 cm & lt; -1 & gt; in wave number) Of the infrared zone. The instrument used for the ultraviolet spectrophotometer, visible spectrophotometer (or colorimeter), infrared spectrophotometer or atomic absorption spectrophotometer. In order to ensure the accuracy and accuracy of the measurement, all instruments shall be regularly calibrated in accordance with the national metrological verification procedures or the provisions of this appendix.
Spectrophotometer spectral range: including the wavelength range of 400 ~ 760nm visible region and the wavelength range of 200 ~ 400nm ultraviolet light, different light source has its unique emission spectrum, so you can use different light as the instrument light source.
Tungsten lamp emission spectrum: the tungsten light source issued by the wavelength of 400 ~ 760nm spectral light through the prism refraction, can be obtained by the red orange, yellow green, blue indigo, purple composition of the continuous chromatography; the chromatogram can be used as a visible spectrophotometer light source.
Hydrogen lamp (or deuterium lamp) emission spectrum: hydrogen lamp can send 185 ~ 400nm wavelength spectrum can be used as a UV light source.
The absorption spectrum of matter (1)
If a solution of a substance is placed between the light source and the prism, the spectrum displayed on the screen is no longer the spectrum of the light source, and there are several dark lines, that is, the light of some wavelengths in the light emission spectrum Solution absorption and disappear, this solution is absorbed after the spectrum known as the absorption spectrum of the solution. The absorption spectra of different substances are different, so according to the absorption spectrum, can identify the solution contained in the material.
The absorption spectrum of matter (2)
When the light passes through the solution of a substance, the intensity of the light transmitted is weakened because a part of the light is reflected or dispersed on the surface of the solution, and a part of the light is absorbed by the substance constituting the solution, and only a part of the light can penetrate the solution.
Incident light = reflected light + scattered light + absorption light + through light.
If we use distilled water (or the solvent that makes up the solution) as a "blank" to correct the loss of incident light caused by factors such as reflection, dispersion, etc.:
Incident light = absorb light ten through light