Identification of Chlorophyll a-f and Microbial Diversity Using UV-Vis-NIR Spectroscopy

Chlorophyll (Chl) is a pigment related to photosynthesis that is the primary basis for life on Earth. Chlorophyll’s primary function within a chloroplast is to absorb light. Many researchers have invested their time into fully understanding and quantifying chlorophyll as a means of understanding the environment. Scientists have been able to separate Chlorophyll into many categories including Chl-a, Chl-b, Chl-c1, Chl-c2, Chl-d, Chl-f using UV-Vis-NIR spectroscopy.

Chl-a is the most common pigment present in almost every photosynthesizing organism. Chl-b is found in certain plants like English spinach. Chl-c1 and Chl-c2 can be found in certain algae. Chl-d and Chl-f can be found in cyanobacteria. Each type of chlorophyll is identified by a shift in its absorption feature along with where it can be commonly found.

Figure 1: Graph of absorption measurements of Chl in acetone solution.
https://rseco.org/content/122-chlorophyll-absorption-and-photosynthetic-action-spectra.html

Studies into chlorophyll pigments primarily target UV-Vis since this is where most of their absorption features are. Using the differences in absorption features from the types of Chl as well as the features from the pigments and cell structure it is possible to perform speciation on algae and microbiology using spectroradiometers like the PSR-1100f and the NaturaSpec™ from Spectral Evolution.

Thanks to the high spectral resolution and sensitivity of Spectral Evolution’s instruments, the absorption features of the different types of Chlorophyll as well as the features from the pigments and cell structure can clearly be distinguished. Spectroradiometers like the PSR-1100f and the NaturaSpec™ provide a solution to perform speciation on algae, vegetation and microbiology.

The study of microbial growth and diversity is critical to understanding environmental health, human health, and even climate change. These processes can be measured terrestrially, aquatically, and in the lab.

Figure 2: (Left) Spectra of filtered water from various depths of Salt Pond on 8/3/18, normalized to the volume of sample filtered.
(Right) sample filters organized by depth. Groups of pigmented microbes who capture light at lower wavelengths decrease in relative abundance as depth increases.

In Figure 2 a researcher from University of Southern California identifies absorbance features for different kinds of chlorophyll to give an understanding of the microbial populations by depth using the PSR-1100f. They achieve this by using absorbance spectroscopy to characterize the spectral peaks of pigments and cell structure of the different algae in the water column.

Spectral Evolution’s UV-Vis-NIR field-portable spectroradiometers are rugged and specifically designed for the challenges of environmental remote sensing. Our NIR spectroradiometers offer the best combination of high resolution and high sensitivity resulting in the most precise spectral data from any field instrument available on the market. The wide variety of accessories & fore optics make our instruments the most versatile spectroradiometers for all types of measurements, including reflectance, radiance, irradiance, & transmittance.

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