Supercritical fluid extraction (SFE) of 4(5)-methylimidazole (4-MeI) and 2-acetyl-4(5)-(1,2,3,4)-tetrahydroxybutyl-imidazole (THI) from ground-coffee with high-performance liquid chromatographic-electrospray mass spectrometric quantification (HPLC/ESI-MS).
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 (CO2) 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 x 2.1 mm, 3 microm) with 80% methanol and 20% 0.01 mol l-1 ammonium formate as the mobile phase. The limit of quantification was around 1.5 pg for 4-MeI and 2.0 pg 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 <4% (n = 6). Accuracy was in the range 98-101%; recovery rates were > or = 98 and > or = 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.
Lojková
L
L
Department of Chemistry and Biochemistry, Mendel University of Agriculture and Forestry Brno, Zemedelská 1, CZ-613 00 Brno, Czech Republic.
Klejdus
B
B
Moravcová
J
J
Kubán
V
V
D002851:Chromatography, High Pressure Liquid / Q000379:methods; D025924:Chromatography, Supercritical Fluid / Q000379:methods; D003069:Coffee / Q000737:chemistry*; D005504:Food Analysis / Q000379:methods; D005506:Food Contamination / Q000032:analysis*; D007093:Imidazoles / Q000032:analysis / Q000302:isolation & purification*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
D003069:Coffee; D007093:Imidazoles; C049929:2-acetyl-4(5)-tetrahydroxybutylimidazole; C023439:4-methylimidazole