Evolution of Raman spectra in the 2700-3100 1/cm region following the thermal degradation of omega-3 dietary supplements

Abstract

It is well established that the most intense bands in the Raman spectra of substances with molecules containing hydrocarbon chains are localized in the region of 2700-3100 1/cm. Nevertheless, this spectral range is rarely employed for the analysis of such substances. In this study, we examined the Raman spectra of dietary supplements with varying contents of omega-3 polyunsaturated fatty acids (ω-3 PUFA) and their evolution under thermal degradation. We found out that the overall spectrum profile in the 2700-3100 1/cm region, for both degraded and undegraded samples, is determined by the relative content of ω-3 PUFAs. The most intense bands in this range are observed at 2852, 2875, 2933 and 3015 1/cm. The peaks around 2852 and 2875 1/cm are assigned to the vibrations of CH2 groups in saturated segments of hydrocarbon chains, and the bands around 2933 and 3015 1/cm correspond to the vibrations of C-H groups in unsaturated segments. It was revealed that the intensity ratio of the bands at 3015 and 2875 1/cm is the most useful for the assessment of the ω‑3 PUFAs content in dietary supplements if these acids are present in the form of ethyl esters. When they occur as triglycerides, the intensity ratio of the bands at 3015 and 2852 1/cm serves as the best indicator. The obtained results could be employed in the development of express methods for assessing the commercial products quality.
This work was supported by the RSF grant № 24-22-20100, https://rscf.ru/project/24-22-20100/

Speaker

Dmitry Vasimov
Prokhorov General Physics Institute of the Russian Academy of Sciences
Russia

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