title: Rapid Quantitative Determination of Squalene in Shark Liver Oils by Raman and IR Spectroscopy.
abstract: Squalene is sourced predominantly from shark liver oils and to a lesser extent from plants such as olives. It is used for the production of surfactants, dyes, sunscreen, and cosmetics. The economic value of shark liver oil is directly related to the squalene content, which in turn is highly variable and species-dependent. Presented here is a validated gas chromatography-mass spectrometry analysis method for the quantitation of squalene in shark liver oils, with an accuracy of 99.0 %, precision of 0.23 % (standard deviation), and linearity of >0.999. The method has been used to measure the squalene concentration of 16 commercial shark liver oils. These reference squalene concentrations were related to infrared (IR) and Raman spectra of the same oils using partial least squares regression. The resultant models were suitable for the rapid quantitation of squalene in shark liver oils, with cross-validation r (2) values of >0.98 and root mean square errors of validation of ≤4.3 % w/w. Independent test set validation of these models found mean absolute deviations of the 4.9 and 1.0 % w/w for the IR and Raman models, respectively. Both techniques were more accurate than results obtained by an industrial refractive index analysis method, which is used for rapid, cheap quantitation of squalene in shark liver oils. In particular, the Raman partial least squares regression was suited to quantitative squalene analysis. The intense and highly characteristic Raman bands of squalene made quantitative analysis possible irrespective of the lipid matrix.
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited, PO Box 5114, Nelson, 7010, New Zealand.
authors.forename: David W
authors.initials: DW
authors.lastname: Hall
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited, PO Box 5114, Nelson, 7010, New Zealand.
authors.forename: Susan N
authors.initials: SN
authors.lastname: Marshall
authors.affiliation: Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.
authors.forename: Keith C
authors.initials: KC
authors.lastname: Gordon
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited, PO Box 5114, Nelson, 7010, New Zealand. Daniel.killeen@plantandfood.co.nz.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Killeen
mesh_terms: D000818:Animals; D005395:Fish Oils / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D008099:Liver / Q000737:chemistry*; D015394:Molecular Structure; D012754:Sharks; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D013185:Squalene / Q000032:analysis*
chemical_list: D005395:Fish Oils; D013185:Squalene
keywords: Gas chromatography; Infrared; Mass spectrometry; Partial least squares regression; Raman; Shark liver; Squalene