Two polar analytes, 4(5)-methylimidazole (4-MeI) and 2-acetyl-4(5)-(1,2,3,4)-tetrahydroxybutyl-imidazole (THI), were extracted with supercritical carbon dioxide (CO 2 ) modified with aqueous methanol. The method was applied to a roasted coffee powder with good recovery rates. Method efficiency was compared with that of solid-phase extraction using SCX Disc cartridges and validated for spiked solid matrix. The analytes were determined using isocratic liquid chromatography-mass spectrometry (LC/MS) on an Atlantis HILIC Silica column (150×2.1mm,3µm) with 80% methanol and 20% 0.01moll −1 ammonium formate as the mobile phase. The limit of quantification was around 1.5pg for 4-MeI and 2.0pg for THI. The linearity of the calibration curves was satisfactory as indicated by correlation coefficients of >0.999. The coefficient of variation for the intra-day and inter-day precisions was n =6). Accuracy was in the range 98–101%; recovery rates were≥98 and≥99% for THI and 4-MeI, respectively. Several samples of Arabica coffee from various locations and commercially available ‘off-the-shelf' coffee products (Arabica/Robusta mixtures) were analysed to test the method.
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Supercritical fluid extraction;
liquid chromatography-mass spectrometry (LC/MS);
Document Type: Research Article
Department of Chemistry and Biochemistry, Mendel University of Agriculture and Forestry Brno, Zemědělská 1, CZ-613 00 Brno, Czech Republic
Department of Chemistry of Natural Compounds, Institute of Chemical Technology, Technická 5, CZ-166 28 Prague, Czech Republic
October 1, 2006
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