Establishment of reliable mass spectra and retention indices library: Identification of fatty acids in human plasma without authentic standards

Discrimination between the Triglyceride Form and the Ethyl Ester Form of Fish Oil Using Chromatography-Mass Spectrometry

Although the triglyceride form is the natural form of fish oil found in fish, the ethyl ester form of fish oil, which is used during processing to save costs, is also present on the market. In this study, fatty acids and lipids were determined using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-linear ion trap mass spectrometry (LC-LIT/MS), respectively, according to developed methods. The identification of fatty acids was based on the mass spectral characteristics and equivalent chain lengths. However, the fatty acid contents of both forms of fish oils are quite similar. The application of the LC-LIT/MS method for the structural characterization of triacylglycerols (TAGs) and the mechanism of LIT/MS fragmentation are also discussed. Neutral losses of CH2=CH2 (m/z 28) and CH3CH2OH (m/z 46), which are LIT/MS characteristics of ethyl ester from fish oil, were found for the first time. The triglyceride form of fish oils was easily and accurately identified using fingerprint chromatography. In conclusion, lipid analysis combined with LC-LIT/MS showed an improved capability to distinguish between types of fish oil.

Rapid and label-free metamaterial-based biosensor for fatty acid detection with terahertz time-domain spectroscopy

A rapid method for detecting fatty acids (FAs) using terahertz time-domain spectroscopy (THz-TDS) technology combined with a metamaterial-based THz sensor was developed. We measured the THz responses to oleic acid, linoleic acid and α-linoleic acid with different numbers of double-bond, α-linoleic acid and γ-linoleic acid with different conformations. In addition, in order to explore the reason for the observed redshifts of the resonance frequencies of the four FAs, the dielectric constants of the FAs were measured in the THz region. Furthermore, the four fatty acids were also attempted to be identified by Raman spectroscopy, which was difficult to accomplish unambiguously because of the effect of fluorescence. This result thus demonstrates the power and usefulness of metamaterial-assisted THz-TDS in the rapid determination of the FAs, and its potential as a versatile tool for investigation of biological metabolism, and for food product quality, safety inspection and control.

Classification and adulteration detection of vegetable oils based on fatty acid profiles

The detection of adulteration of high priced oils is a particular concern in food quality and safety. Therefore, it is necessary to develop authenticity detection method for protecting the health of customers. In this study, fatty acid profiles of five edible oils were established by gas chromatography coupled with mass spectrometry (GC/MS) in selected ion monitoring mode. Using mass spectral characteristics of selected ions and equivalent chain length (ECL), 28 fatty acids were identified and employed to classify five kinds of edible oils by using unsupervised (principal component analysis and hierarchical clustering analysis), supervised (random forests) multivariate statistical methods. The results indicated that fatty acid profiles of these edible oils could classify five kinds of edible vegetable oils into five groups and are therefore employed to authenticity assessment. Moreover, adulterated oils were simulated by Monte Carlo method to establish simultaneous adulteration detection model for five kinds of edible oils by random forests. As a result, this model could identify five kinds of edible oils and sensitively detect adulteration of edible oil with other vegetable oils about the level of 10%.