Simultaneous Determination of 2-Methylimidazole, 4-Methylimidazole and 2-Acetyl-4-(1,2,3,4-tetrahydroxybutyl) imidazole in Caramel Colours by Solid Phase Extraction-High Performance Liquid Chromatography

An analytical method was developed to extract and determine 2-methylimidazole (2-MEI), 4-methylimidazole (4-MEI) and 2-acetyl-4-( 1,2,3,4-tetrahydroxybutyl) imidazole (THI) in caramel colors using solid phase extraction and high performance liquid chromatographic (SPE-HPLC). Caramel colours were dissolved in water and enriched and purified by strong cation exchange solid phase extraction. Then the purified solution was separated by Polaris C sub(18)-A (250 mmx4.6 mm, 5 mu m) column and 2-MEI and 4-MEI were measured at UV wavelength of 215 nm and THI at UV wavelength of 287 nm with a mobile phase consisting of acetonitrile (A) and 0.05% ammonia in water (B) in proportion of A: B = 10:90 (V/V). The flow rate was 0.6 mL/min. The method had good linearity within the concentration range of 0.2-20 mg/L with correlation coefficients of greater than 0.9996. The recoveries of 2-MEI, 4-MEI and THI were between 75.3%-93.4% and relative standard deviations (RSD) were less than 10% at three spiked level of 10 mg/kg, 25 mg/kg and 100 mg/kg. The limits of detection (LOD) were 2.6, 3.0 and 1.5 mg/kg and the limits of quantitation (LOQ) were 8.5, 10.0 and 5.0 mg/kg, respectively.