Chlorophyll meter principle
According to the absorption of the visible spectrum by the chloroplast pigment extract, the absorbance is measured at a specific wavelength by a spectrophotometer, and the content of each pigment in the extract can be calculated by the formula. According to Lambert-Beer's law, the absorbance A of a colored solution is proportional to the solute concentration C and the thickness L of the liquid layer, that is, A = αCL: α proportional constant.
When the solution concentration is in units of percentage concentration and the thickness of the liquid layer is 1 cm, α is the absorption coefficient of the substance. The absorption coefficient of various colored substance solutions at different wavelengths can be obtained by measuring the absorbance of pure substances at known wavelengths at different wavelengths.
If there are several kinds of light absorbing substances in the solution, the total absorbance of the mixed liquid at a certain wavelength is equal to the comprehensive absorbance of each component at the corresponding wavelength. This is the additivity of absorbance. To determine the content of chlorophyll a, b and carotenoids in the chloroplast pigment extract, it is only necessary to determine the absorbance A of the extract at three specific wavelengths, and according to the chlorophyll a, b and carotenoids at this wavelength. The absorbance coefficient can be used to determine the concentration. In order to eliminate the interference of carotenoids when measuring chlorophyll a and b, the wavelength of monochromatic light used selects the maximum absorption peak of chlorophyll in the red region.
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