Application Of Vibrational Spectroscopy for Determining the Monomer Composition of Alginate

abstract

English

In recent years, interest has grown in developing innovative chemical and biological soil amendments within the framework of sustainable agriculture. An innovative approach in the production of soil bioinoculants involves the recently proposed technique of self-entrapment of Plant Growth-Promoting Rhizobacteria (PGPR) through the gelation of their own extracellular polysaccharides. A common method for the gelation of sodium alginate utilizes multivalent cations, such as calcium ions (Ca²⁺), which facilitate cross-linking and network formation within the alginate structure. However, the efficiency of alginate gelation and the stability of the resulting gels depend on three key structural parameters of the polymer: molecular weight, (de)acetylation, and monomer composition. These factors influence the physical properties of the hydrogel, including strength, porosity, and biodegradability—qualities essential for its effectiveness as a carrier for PGPR. Understanding and optimizing these parameters can enhance the functionality and reliability of alginate-based bioinoculants. To analyze the monomer composition of sodium alginate, which is made up of L-guluronic acid (poly-G) and D-mannuronic acid (poly-M) blocks, we used ATR-FTIR, Raman microspectroscopy, and FT-Raman spectroscopy. First, a series of calibration samples were prepared from mixtures of commercial standards of poly-G and poly-M, providing a controlled basis for analysis and allowing precise spectral measurements. The results were analyzed using principal component analysis (PCA), a method that identifies directions of highest variability within the spectral data. PCA enabled the identification of two significant peaks corresponding to the influence of monomer composition on the analyzed spectrum, observed at 820 and 950 cm⁻¹. The ratio of these peaks correlated with the known poly-G content in each calibration sample. Consequently, calibration curves were established for all tested spectroscopic techniques, enabling quantification of poly-G concentration in commercial sodium alginate samples. In conclusion, this study presents a promising method for determining poly-G concentration in sodium alginate using vibrational spectroscopy techniques. However, further research is required to validate and refine this approach. Exploring additional methodologies will be crucial for confirming our findings and improving the accuracy and reliability of this analytical technique, ultimately contributing to more precise characterizations of sodium alginate in various applications, including the research and development of alginate-based bioinoculants.

Sodium alginate; ATR-FTIR; Raman microspectroscopy; Sustainable agriculture

PŘIBYL, J.; KIANIČKA, M.; SEDLÁČEK, P.

28. 11. 2024

978-80-214-6298-4

Studentská odborná konference Chemie je život 2024 - Sborník abstraktů

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