Applicability of MTBE lipid extraction assisted by microwave in pistachio oil and fatty acids characterization by mono- and two-dimensional gas chromatography

This study aims to demonstrate the applicability of MTBE-based extraction solvents for routine food analysis, particularly in the profiling of fatty acid methyl esters (FAMEs). To enhance both applicability and throughput, the extraction was also performed using microwave-assisted extraction (MAE), which offers several advantages over conventional methods, significantly reducing extraction times and solvent consumption [1].
As a case study, unroasted, unsalted pistachio nuts from Bronte (Sicily, Italy) were analyzed. MTBE, combined with MAE, was tested both as a single solvent and in a mixture with methanol and water, following the same composition as the traditional Matyash method. The MAE approaches were compared against Soxhlet extraction using different solvents (n-hexane, MTBE, and diethyl ether) and the conventional Matyash method, both considered gold standards for lipid extraction [2].
The extraction methods were assessed based on total lipid yield and fatty acid (FA) composition, following their derivatization into methyl esters (MEs). FAMEs were analyzed using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) for qualitative evaluation and a GC system with a flame ionization detector (FID) for semi-quantification.
To evaluate the efficiency of the extraction methods and the variability in FAME profiles among different lipid extractions, a one-way analysis of variance (ANOVA) followed by Tukey’s HSD post-hoc test was conducted to determine statistical differences in lipid yield and FAME composition. Additionally, the greenness of the applied extraction methods was assessed using the AGREEPrep metric [3].

Literature:
[1]- D. Ferrara, M. Beccaria, C. E. Cordero, and G. Purcaro, “Microwave- Assisted Extraction in Closed Vessel in Food Analysis,” Journal of Separation Science 46 (2023): 2300390

[2]- Vitali Matyash, Gerhard Liebisch, Teymuras V. Kurzchalia, Andrej Shevchenko, Dominik Schwudke; 2008; Lipid extraction by methyl-tert-butyl ether for high-throughput lipidomics; Journal of Lipid Research; Volume 49; Pages 1137-1146.

[3]- Francisco Pena-Pereiraa, Marek Tobiszewski b, Wojciech Wojnowski, Elefteria Psillakis; 2022; A Tutorial on AGREEprep an Analytical Greenness Metric for Sample Preparation; Advances in Sample Preparation; Volume 3¸Pages 100045.