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 C18-A( 250 mm × 4. 6 mm,5 μm) 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 m L / 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 between75. 3%- 93. 4% and relative standard deviations( RSD) were less than 10% at three spiked level of10 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.