Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are commercially important omega-3 fatty acids found in fish oils. Here we demonstrate that a handheld Raman spectrometer can be used to quantitate these compounds in intact fish oil capsules, avoiding oxidizing risk. Partial least squares regression models were prepared by relating Raman spectral variance to EPA and DHA concentrations determined using gas chromatography-mass spectrometry (GC-MS) analysis of fatty acid methyl esters in 15 commercial samples containing 145-473 mg g-1 EPA and 101-260 mg·g-1 DHA. Handheld Fourier transform (FT)-Raman models had root mean square errors of cross-validation of 38 mg g-1, 24 mg g-1, and 32 mg·g-1 for EPA, DHA, and EPA+DHA, respectively. Models generated from a benchtop FT-Raman spectrometer had corresponding errors of 32 mg·g-1, 22 mg·g-1, and 26 mg·g-1. By comparison, average standard deviations from triplicate GC-MS analyses were 11 mg·g-1 for EPA and 9 mg·g-1 for DHA.
Keywords: Fish oil; docosahexaenoic acid; eicosapentaenoic acid; handheld Raman; omega-3; softgel capsule.