DETERMINATION OF 4-METHYLIMIDAZOLE AND 2-ACETYL-4-TETRAHYDROXY-BUTYLIMIDAZOLE IN CARAMEL COLOR AND PRODUCTS BY LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY

Abstract

The simultaneous determination of 4-MEI and THI in caramel and products by LC-MS/MS was developed with several advantages of simplicity, selectivity, and high sensitivity. Chromatographic separation was performed using a C18 column (100 × 2.1 mm, 1.7 μm), with a mobile phase consisting of ammonium formate pH = 4 and acetonitrile containing 0.1% formic acid employing a gradient elution mode. The analytes were detected using an MS/MS double mass spectrometer with an ESI+ ionization source. Samples were cleaned and enriched on a SPE MCX column. Method validaion resulted in a linear range of 5.0 - 500 ppb for 4-MEI, and 1.0 - 500 for THI, with LODs of 0.30 g/kg for THI and 1.5 μg/kg for 4-MEI, and LOQs of 1 μg/kg for THI and 5 μg/kg for 4-MEI. Repeatability and reproducibility for 4-MEI ranged from 2.9% to 9.1% and 2.9% to 11.8%, respectively, and for THI from 3.5% to 9.4% and 4.8% to 11.5%, respectively. Recovery rates for with 4-MEI and THI met AOAC's requirements, ranging from 82.7% to 106.4% and 87.2% to 109.7%, respectively. Application of the analytical method for 24 market products, including caramel, beverages, condiments, and cakes, showed that the 4-MEI and THI concentrations in consumer products were within the permissible limits, while pure caramel samples exceeded the permissible limits for THI concentrations.