title: Simple and Fast Sample Preparation Followed by Gas Chromatography-Tandem Mass Spectrometry (GC-MS/MS) for the Analysis of 2- and 4-Methylimidazole in Cola and Dark Beer.
abstract: We have developed a simple and fast sample preparation technique in combination with a gas chromatography-tandem mass spectrometry (GC-MS/MS) for the quantification of 2-methylimidazole (2-MeI) and 4-methylimidazole (4-MeI) in colas and dark beers. Conventional sample preparation technique for GC-MS requires laborious and time-consuming steps consisting of sample concentration, pH adjustment, ion pair extraction, centrifugation, back-extraction, centrifugation, derivatization, and extraction. Our sample preparation technique consists of only 2 steps (in situ derivation and extraction) which requires less than 3 min. This method provided high linearity, low limit of detection and limit of quantification, high recovery, and high intra- and interday repeatability. It was found that internal standard method with diluted stable isotope (4-MeI-d6) and 2-ethylimidazole (2-EI) could not correctly compensate the matrix effects. Thus, standard addition technique was used for the quantification of 2- and 4-MeI. The established method was successfully applied to colas and dark beers for the determination of 2-MeI and 4-MeI. The 4-MeI contents in colas and dark beers ranged from 8 to 319 μg/L and from trace to 417 μg/L, respectively. Small quantity (0 to 8 μg/L) of 2-MeI was found only in dark beers. The contents of 4-MeI (22 μg/L) in colas obtained from fast food restaurants were significantly lower than those (177 μg/L) in canned or bottled colas.
authors.affiliation: Dept. of Food and Biotechnology, Graduate School, Woosuk Univ., Jeonbuk Province, 565-701Samnye-eup, Wanju-gun, Jeonbuk Province, 565-701, South Korea.
authors.forename: Sol Ji
authors.initials: SJ
authors.lastname: Choi
authors.affiliation: Dept. of Food and Biotechnology, Graduate School, Woosuk Univ., Jeonbuk Province, 565-701Samnye-eup, Wanju-gun, Jeonbuk Province, 565-701, South Korea.|Agricultural and Food Product Safety Analysis Center, Woosuk Univ., Jeonbuk Province, 565-701, South Korea.
authors.forename: Mun Yhung
authors.initials: MY
authors.lastname: Jung
mesh_terms: D001515:Beer / Q000032:analysis*; D030221:Cola / Q000737:chemistry*; D005504:Food Analysis; D008401:Gas Chromatography-Mass Spectrometry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000032:analysis*; D057230:Limit of Detection; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry
chemical_list: C510842:2-ethylimidazole; D007093:Imidazoles; C023439:4-methylimidazole; C032655:2-methylimidazole
keywords: 2- and 4-methylimidazole; cola; dark beer; gas chromatography-tandem mass spectrometry; in situ derivatization