Lipid extraction assisted by microwave using methyl tert-butyl ether as based solvent for extraction and fatty acids characterization of pistachio oil by mono- and two- dimensional gas chromatography

This study demonstrates the applicability of microwave-assisted extraction (MAE) methods using methyl tert-butyl ether (MTBE) asbased solvent for lipid extraction from unsalted and unroasted pistachio. MAE was performed using MTBE as a single extraction solvent and in a mixture with methanol and water following the same composition used in the Matyash method (MTBE/CH3OH/H2O, 10/3/2.5, v/v/v). The MAE approaches were compared with Soxhlet extraction using three different solvents with three different polarities (n-hexane, diethyl ether and MTBE) and with the conventional Matyash method, both considered gold standards methodologies for lipid extraction [1]. Fatty acids (FAs) were derivatized into FA methyl esters (MEs) and were analysed through gas chromatography with flame ionization detection (GC-FID) for quantitative analysis, and comprehensive two-dimensional GC coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) for qualitative profiling. To assess the efficiency of the extraction methods and the variability in FAMEs profile among the different approaches, a one-way analysis of variance (ANOVA) followed by Tukey’s HSD post-hoc test was performed to assess statistically significant differences in lipid yield and FA composition among the extraction methods. Finally, the greenness of the different methods was evaluated using AGREEprep metric [2] which indicated that the MAE-MTBE approach was the best in terms of greenness among those examined.

References
[1] V. Matyash, G. Liebisch, T. V. Kurzchalia, A. Shevchenko, D. Schwudke; Journal of Lipid Research; 2008; Volume 49; 1137.
[2] F. Pena-Pereiraa, M. Tobiszewski, W. Wojnowski, E. Psillakis; Advances in Sample Preparation; 2022; Volume 3; 100045.