Determination of 4(5)-methylimidazole in carbonated beverages by isotope-dilution liquid chromatography-tandem mass spectrometry

Abstract

The purpose of this study was to develop a method to quantify 4(5)-methylimidazole (4-MEI), a suspected carcinogen, in carbonated beverages by simple sample dilution and isotope-dilution reverse-phase LC-MS/MS. Isotope dilution using hexa-deuterated methylimidazole (d₆-4-MEI) was used to quantify native 4-MEI and to assess matrix effects quantitatively. The accuracy of the method was assessed by intentionally fortifying a negative control sample at three doses: low, medium and high (replicates of n = 5 each) with a known amount of 4-MEI. The respective absolute error in each case was 18.7 ± 0.7%, 14.6 ± 2.8% and 21.1 ± 9.7%. Within-day (intra-) and day-to-day (inter-) repeatability, determined as the relative standard deviation by fortifying a negative control sample (n = 5), were 9.5% and 15.4%, respectively. Average ion suppression of d₆-4-MEI in beer was 63.9 ± 3.2%, while no suppression or enhancement was seen in non-alcoholic samples. The instrument and method limit of detection were calculated as 0.6 and 5.8 ng ml^–1, respectively. 4(5)-Methylimidazole was quantified in a variety of store-bought consumer beverages and it was found that in many of the samples tested consuming a single can of beer would result in intake levels of 4-MEI that exceed the no significant risk guideline of 29 µg day^–1. Conversely, 4-MEI in the samples was orders of magnitude smaller than the European Food Safety Authority acceptable daily intake threshold value of 100 mg kg^–1 bw day^–1.

Graphical Abstract

Keywords:

• 4-methylimidazole
• electrospray
• isotope dilution
• reversed phase
• liquid chromatography
• mass spectrometry
• carbonated beverages

Acknowledgements

Kerri Pleskach, Department of Fisheries and Oceans, is acknowledged for help with the method development steps. This work was conducted in part by G.R. as part of his grade 9 science project in collaboration with T.H. and G.T.T. at the Manitoba School Science Symposium, where G.R. presented these results as a poster. G.R. won the Analytical Sciences Award from the Mid Canada Association of Analytical Chemistry, a Canada Institute of Food Science and Technology award and a Gold Medal.

Additional information

Funding

G.R. won the Analytical Sciences Award from the Mid Canada Association of Analytical Chemistry and a Canada Institute of Food Science and Technology award.