Developing qualitative extraction profiles of coffee aromas utilizing polymeric ionic liquid sorbent coatings in headspace solid-phase microextraction gas chromatography–mass spectrometry
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Two solid-phase microextraction (SPME) sorbent coatings based on polymeric ionic liquids (PILs) have been utilized for the analysis of complex coffee aroma samples. The PIL-based SPME coatings examined, namely, poly(1-(4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide) [poly(VBHDIm+ NTf 2 − )], with ∼14-μm thickness, and poly(1-vinyl-3-hexylimidazolium chloride) [poly(ViHIm+ Cl−)], with ∼8-μm thickness, were employed for the headspace determination of up to 49 analytes from four different coffee beans: two French roast coffees of different brands, Sumatra coffee, and decaffeinated Sumatra coffee. The analysis was conducted using gas chromatography coupled to mass spectrometry. For comparative purposes, the commercial polyacrylate (PA, 85-μm film thickness) SPME coating was utilized under the same extraction conditions. The three SPME coatings tested behaved quite differently as a function of the families of compounds extracted. Thus, the poly(VBHDIm+ NTf 2 − ) coating was extremely selective for aldehydes while also exhibiting good extraction efficiencies for acids. The poly-(ViHIm+ Cl−) coating exhibited superior performance for aromatic alcohols, and the PA coating worked better for heterocyclic aromatics. Both PIL-based SPME sorbent coatings demonstrated exceptional selectivity and extraction efficiency when dealing with complex coffee aromas in spite of their small film thicknesses.
KeywordsSolid-phase microextraction Coffee analysis Coffee aroma Gas chromatography Headspace analysis Ionic liquid
The authors wish to thank Qichao Zhao, Christa Graham, and Yunjing Meng for their assistance and useful discussions. J.L.A. thanks funding from the Analytical and Surface Chemistry Program in the Division of Chemistry and the Separation and Purification Process Program in the Chemical, Environmental, Bioengineering, and Transport Systems Division from the National Science Foundation for a CAREER grant (CHE-0748612). A.M.A. acknowledges funding from the Spanish Ministry of Innovation and Science (MICINN), project ref. CTQ2008-06253/BQU, and from the Canary Agency for Research and Innovation (ACIISI) reinforcement, project ref. SolSubC20081000171. V.P. thanks the MICINN for the Ramón y Cajal contract with the University of La Laguna (ULL). J.L.D. thanks the ACIISI for the contract with the ULL and funding for the stay at The University of Toledo.
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