Determination of Caramel Color and 4-Methylimidazole Content in Food
A high performance liquid chromatography(HPLC)method for determining the content of caramel color in food was established,combined with ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)method for determining the content of 4-methylimidazole.After adding water for ultrasonic extraction,the sample was centrifuged and the supernatant was purified by MCX column.The initial effluent was collected and precipitated with 4 times ethanol.After centrifugation,the supernatant was discarded and the precipitate was redissolved in water before measuring caramel color,4-methylimidazole collects ammonia water methanol eluate,and after nitrogen blowing,it was redissolved in the initial mobile phase.Caramel color was prepared using a 10 mmol/L sodium dihydrogen phosphate solution as the mobile phase using a Shiseido SCX column(4.6 mm×150 mm,5 μm).Using a chromatographic column with equal elution,measure at a wavelength of 610 nm.4-methylimidazole was eluted with a gradient of 10 mmol/L ammonium acetate aqueous solution containing 0.1％formic acid and acetonitrile as the mobile phase,and passed through a Shiseido HILIC column(2.1 mm×100 mm,3 μm).After chromatographic column separation,quantitative analysis was performed using a multi reaction monitoring mode and internal standard method.Caramel color and 4-methylimidazole showed good linearity in their respective concentration ranges.The results from three-level spiked recoveries showed that the average recovery rates from caramel color were 80.5％-94.2％,with relative standard deviations of 3.3％-7.8％.The detection limit for solid samples were 0.02 g/kg,and for liquid samples were 0.02 g/L.The average recovery rates of 4-methylimidazole were 85.3％-106.2％,with a relative standard deviations of 3.1％-6.9％.The detection limit for solid samples were 1.0 μg/kg,detection limit for liquid samples were 1.0 μg/L.This method optimizes the pre-treatment process and instrument chromatographic conditions,effectively controls matrix interference,and has high sensitivity,good reproducibility,and strong anti-interference ability.It was suitable for the detection of caramel color and 4-methylimidazole in foods such as soy sauce,rice vinegar,cola,and yellow wine.
caramel color4-methylimidazolehigh performance liquid chromatographyultra-high performance liquid chromatography-tandem mass spectrometry
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