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Stable isotope ratios of carbon and hydrogen to distinguish olive oil from shark squalene-squalane



Squalene and its hydrogenated derivate squalane are widely used in the pharmaceutical and cosmetic fields. The two compounds are mainly produced from the liver oil of deep sea sharks and from olive oil distillates. Squalene and squalane from shark cost less than the same compounds derived from olive oil, and the use of these shark-derived compounds is unethical in cosmetic formulations. In this work we investigate whether 13C/12C and 2H/1H ratios can distinguish olive oil from shark squalene/squalane and can detect the presence of shark derivates in olive oil based products. The 13C/12C ratios (expressed as δ13C values) of bulk samples and of pure compounds measured using isotope ratio mass spectrometry (IRMS) were significantly lower in authentic olive oil squalene/squalane (N: 13; −28.4 ± 0.5‰; −28.3 ± 0.8‰) than in shark squalene/squalane samples (N: 15; −20.5 ± 0.7‰; −20.4 ± 0.6‰). By defining δ13C threshold values of −27.4‰ and −26.6‰ for olive oil bulk and pure squalene/squalane, respectively, illegal addition of shark products can be identified starting from a minimum of 10%. 2H/1H analysis is not useful for distinguishing the two different origins.

δ13C analysis is proposed as a suitable tool for detecting the authenticity of commercial olive oil squalene and squalane samples, using IRMS interfaced to an elemental analyser if the purity is higher than 80% and IRMS interfaced to a gas chromatography/combustion system for samples with lower purity, including solutions of squalane extracted from cosmetic products. Copyright © 2010 John Wiley & Sons, Ltd.