Spectrophotometer with a can produce multiple wavelengths of light source, through a series of spectroscopic device, resulting in a specific wavelength of light source, light through the test samples, part of the light is absorbed, calculate the sample absorbance value, which is converted into the concentration of the sample. Samples of the absorbance value proportional to the concentration of the sample.
Monochromatic light radiation through the material under test solution, the amount of absorbed by the material and the concentration of the material and the thickness of the liquid layer is proportional to the optical path length, the relationship is as follows:
A = - lg (I/I). = - lgT = kLc
Type: A, for the absorbance.
I. For incident light intensity;
I for the transmission of light intensity;
T for the transmittance of materials;
K as the molar absorption coefficient;
L is analyzing the physical optical path, namely, the side length of colorimetric dish;
C is the concentration of the substance;
Material selective absorption wavelength of light, and the corresponding absorption coefficient is the material constants. When a pure substance known under certain conditions is available after the absorption coefficient of the test samples in the same conditions as solution, measure its absorbance, can be calculated from the type test samples in the content of the material. Light absorption in the visible light region, in addition to certain substances, a lot of material itself does not absorb but can join chromogenic reagent in certain conditions or after processing make its color measurement again, so it is also called colorimetric analysis. As chromogenic factors affecting color depth is more, when the poor and often using monochromatic light purity of instrument, so the determination of the application of standard substance and reference substance at the same time.