Determination of 2-methylimidazole, 4-methylimidazole and 2-acetyl-4-(1,2,3,4-tetrahydroxybutyl)imidazole in caramel colours and cola using LC/MS/MS

Substituted imidazoles recently came under scrutiny as they may be indirectly introduced into cola beverages via the use of class IV (E150d) caramel colours and may pose health hazards. A LC/MS/MS method was developed for determining 2- and 4-methylimidazole (2-MI, 4-MI) and 2-acetyl-4-(1,2,3,4)-tetrahydroxybutylimidazole (THI) in beverages and caramel colours. The method is very rapid and easy to conduct as it requires only dilution in eluent for sample preparation. For 4-MI, the recovery was between 94 and 102% for spiked cola samples. The limit of detection was 2 μg/L in the measuring solution (corresponding to 40 μg/L for cola samples diluted 1:20 during sample preparation). 97 cola samples and 13 caramel colours from Germany and France were analysed. From the 3 analytes, only 4-MI was found in the samples with very varying concentrations (non quantifiable traces to 0.6 mg/L in colas and 175–658 mg/kg in E150d). The exposure for cola drinkers in worst case scenarios is estimated to be 2–5 μg/kg bodyweight/day, which is judged as being only a low risk for public health.

► LC/MS/MS allows the rapid separation and quantification of three imidazoles.
► No sample preparation besides dilution is needed.
► A survey of about 100 samples was conducted.
► Only 4-methylimidazole (4-MI) was detected in caramel colours and cola beverages.
► The human exposure of 4-MI is judged as being below levels of concern.