Lipids

, Volume 51, Issue 1, pp 139–147 | Cite as

Rapid Quantitative Determination of Squalene in Shark Liver Oils by Raman and IR Spectroscopy

  • David W. Hall
  • Susan N. Marshall
  • Keith C. Gordon
  • Daniel P. Killeen
Methods

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 r2 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.

Keywords

Squalene Shark liver Raman Infrared Partial least squares regression Gas chromatography Mass spectrometry 

Abbreviations

ATR

Attenuated total reflectance

CCD

Charge coupled device

DAGE

Diacylglycerol ether

GC

Gas chromatography

HPLC

High performance liquid chromatography

ICH

International Conference on Harmonization of Technical Requirements

IR

Infrared

MAD

Mean absolute deviation

MS

Mass spectrometry

MUFA

Monounsaturated fatty acids

NIPALS

Non-iterative partial least squares

PLS-R

Partial least squares regression

PUFA

Polyunsaturated fatty acids

RMSEC

Root mean squared error of calibration

RMSEV

Root mean squared error of validation

SNV

Standard normal variate

TAG

Triacylglyerol

Notes

Acknowledgments

This research was supported by funding from the New Zealand Ministry for Business Innovation and Employment (MBIE) for the programme Export Marine Products (C11X1307) and the Dodd-Walls Centre. The authors would like to thank Michael Baird and Mark Gornall of Seadragon Marine Oils Ltd® for providing shark liver oil samples and information.

Compliance with Ethical Standards

Conflict of interest

The authors declare no conflict of interest.

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Copyright information

© AOCS 2015

Authors and Affiliations

  • David W. Hall
    • 1
  • Susan N. Marshall
    • 1
  • Keith C. Gordon
    • 2
  • Daniel P. Killeen
    • 1
  1. 1.The New Zealand Institute for Plant and Food Research LimitedNelsonNew Zealand
  2. 2.Department of ChemistryUniversity of OtagoDunedinNew Zealand

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