Integrated multidimensional and comprehensive 2D GC analysis of fatty acid methyl esters

Abstract

Fatty acid methyl ester (FAME) profiling in complex fish oil and milk fat samples was studied using integrated comprehensive 2D GC (GC × GC) and multidimensional GC (MDGC). Using GC × GC, FAME compounds--cis- and trans-isomers, and essential fatty acid isomers--ranging from C18 to C22 in fish oil and C18 in milk fat were clearly displayed in contour plot format according to structural properties and patterns, further identified based on authentic standards. Incompletely resolved regions were subjected to MDGC, with Cn (n = 18, 20) zones transferred to a (2)D column. Elution behavior of C18 FAME on various (2)D column phases (ionic liquids IL111, IL100, IL76, and modified PEG) was evaluated. Individual isolated Cn zones demonstrated about four-fold increased peak capacities. The IL100 provided superior separation, good peak shape, and utilization of elution space. For milk fat-derived FAME, the (2)D chromatogram revealed at least three peaks corresponding to C18:1, more than six peaks for cis/trans-C18:2 isomers, and two peaks for C18:3. More than 17 peaks were obtained for the C20 region of fish oil-derived FAMEs using MDGC, compared with ten peaks using GC × GC. The MDGC strategy is useful for improved FAME isomer separation and confirmation.

Qualitative analysis of desi ghee, edible oils, and spreads using Raman spectroscopy

“…Figure 6. PCA scatter plot for unknown desi ghee (1-7), unknown olive oils (8-10) and unknown spreads (11)(12)(13) alongwith homemade desi ghee (4).…”

“…In order to ensure their quality, the brands in market must be characterized through reliable, efficient, fast, and economical technique for better health care. Existing chemical methods for the characterization of edible oils are gas chromatography and nuclear magnetic resonance, which are costly, time consuming, and require rigorous sample preparation . During the last decade, Fourier transform infrared spectroscopy has been reported for the analysis of edible oils .…”

“…Existing chemical methods for the characterization of edible oils are gas chromatography and nuclear magnetic resonance, which are costly, time consuming, and require rigorous sample preparation. [9][10][11] During the last decade, Fourier transform infrared spectroscopy has been reported for the analysis of edible oils. [12][13][14][15] However, because of strong absorption band of water and other long chain molecules in the infrared region, the spectroscopic signatures of the ingredients of interest are buried inside the spectra.…”

Total and Free Fatty Acids Analysis in Milk and Dairy Fat

“…The second-dimension separation is generally on a narrow-bore (semi-)polar short (0.5-1 m) column. The separation on this column is extremely fast and results in very narrow peaks with baseline widths of, typically, 0.1-0.6 s. In addition, GC × GC chromatograms are recorded in two dimensions (2D) plots, arising from boiling point and polarity relationships, which facilitate the compounds identification [87].…”

“…Nevertheless, in some cases, they utilized the term "sum of others" referring to some C14:1, C16:1 and C18:1 isomers that were recognized by their position in the 2D plot (not by reference standards), but it is not clear if they were well resolved in the chromatogram or not. More complicated systems, incorporating more columns in multidimensional sets, have been also described with the objective of improving MUFA and PUFA isomers resolution in milk fat [87]. All these efforts resulted in greater number of resolved peaks.…”