Simultaneous determination of diethylene glycol, diethylene glycol monoethyl ether, coumarin and caffeine in food items by gas chromatography

A simple gas chromatography–flame ionisation method was initially developed for the simultaneous determination of the prohibited flavours, namely diethylene glycol (DEG), diethylene glycol monoethyl ether (DEGME) and coumarin in food samples. The analytes were extracted using methanol, and was sonicated for 10 min. The extracts were filtered and directly injected into the GC unit that was fitted with a capillary ATTM-AQUAWAX column. Caffeine, which was found in some of the soft drink samples were also successfully separated. Excellent separation of these flavours and caffeine was achieved in about 23 min. Limit of detection, linear range, and reproducibility of the retention time were evaluated. Average recoveries in the ranges of 93.44–97.54% (RSD, 2.68%) for DEGME, 92.99–101.45% (RSD, 2.99%) for DEG, 90.64–100.00% (RSD, 1.99%) for coumarin and 94.62–97.50% (RSD, 2.54%) for caffeine were obtained. None of the food items analysed was found to contain coumarin, DEG or DEGME. However, of the 35 soft drinks and fruit juices that were analysed, eleven samples were found to contain caffeine, but only one exceeded the legal limit.