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Rapid determination of 4‐methylimidazole in caramel colours using 1 H NMR spectroscopy
Author(s) -
Monakhova Y. B.,
Schlee C.,
Kuballa T.,
Schneider R.,
Lachenmeier D. W.
Publication year - 2012
Publication title -
lebensmittelchemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3811
pISSN - 0937-1478
DOI - 10.1002/lemi.201290114
Subject(s) - chemistry , detection limit , nuclear magnetic resonance spectroscopy , dilution , spectroscopy , molecule , proton nmr , analytical chemistry (journal) , chromatography , matrix (chemical analysis) , nuclear chemistry , organic chemistry , physics , quantum mechanics , thermodynamics
A method utilizing 1 H 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.