Rapid determination of 4‐methylimidazole in caramel colours using 1H NMR spectroscopy

Abstract

AbstractA method utilizing 1H NMR spectroscopy has been developed to measure the concentration of 4‐methylimidazole in caramel colours used as food additive (E150a‐d). For sample preparation, a very simple dilution with water‐ethanol mixture and addition of internal standard is sufficient. 4‐Methylimidazole produces a distinct peak of the methyl group of the molecule in the δ 2.27–2.25 ppm range, where it can be distinguished from other matrix compounds. The method was shown to be of adequate sensitivity with a limit of detection (LOD) of 5.0 mg/L adequate to control the 4‐methylimidazole regulatory limit. The developed method was applied for the analysis of 7 authentic food colourings. Only two products (E150d) contained detectable concentrations of 4‐methylimidazole (662 mg/kg and 401 mg/kg). The NMR method may be used by governmental or industry laboratories for routine control of food colourings.