A.S. Gulin, R.P. Trenkenshu
The A.O. Kovalevsky Institute of Biology of Southern Seas of RAS, RF, Sevastopol, Nachimov Av., 2
The work assesses the efficiency of red light-emitting diodes widely used in phyto-irradiators. The article focuses on the emitting monochrome LED with an extended radiation range in a photometric cell used for determining the concentration of pigments in microalgae cultures,
Spectrophotometric methods are known as the most accurate and relevant methods for assessing the concentration of pigments, having significant advantages for monitoring and controlling the process over chemical ones in terms of selectivity, speed, accuracy, sensitivity, substance consumption, as well as the possibility of continuous analysis in a flow.
The study of the emission spectra of red LEDs, their comparison with the absorption spectra of microalgae cultures, as well as the selection of the most accessible emitting element for the photometric cell is carried out. The analysis of the absorption spectra of the culture and extracts of Dunaliella salina using the method of dividing the long-wavelength region of the spectrum (from 600 to 700 nm) into separate Gaussian curves is presented.
Based on the results obtained, the choice of an LED is made, which has an extended radiation range and allows providing a high sensitivity of the device, with low price making it easy to manufacture a photometric cell. Comparison between the emission spectrum of the LED and the absorption spectrum of the microalgae culture allows us to conclude that the emission spectrum of the LED emitter is in good agreement with the maximum absorption spectrum of the chlorophyll b pigment in the 620–700 nm region, which means that such an emitter is capable of providing a higher energy efficiency. The spectrum of the transmitted light entering the photodetector is also built.
It is concluded that the proposed LED, when used in a photometric cell, can effectively work with pigments in the red region of the spectrum. The obtained device spectra allow determining such culture characteristics as biomass and the ratio of chlorophyll a and chlorophyll b. The transmitted light spectrum allows determining not only the average value of the energy received by the photocell but also the amount of pigments.
Keywords: LED, chlorophyll a, chlorophyll b, emission spectrum, absorption spectra, Gaussians, system of automatic control of microalgae growth.
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