Resumen de 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
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 situderivation 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. A fast sample preparation technique in combination with GC-MS/MS for the analysis of 2- and 4-MeI has been developed. The sample preparation is very simple and takes less than 3 min. The analytical method was selective, precise, and accurate. The method would be a simple and reliable tool for the quantification of 2-MeI and 4-MeI in cola and dark beers.
