Analysis of illegal colourants (citrus red II, diethyl yellow, dimethyl yellow, metanil yellow and rhodamine B) in foods by LC-UV and LC-MS/MS

Synthetic colourants are highly regulated due to their correlation with a variety of health hazards. Regulatory services must be able to detect the substances in a cost-effective, efficient, and sensitive manner. LC-UV and LC-MS/MS methods have been developed to simultaneously detect five illegal colourants in foods, such as: citrus red II, diethyl yellow, dimethyl yellow, metanil yellow, and rhodamine B. This method showed good linearity (R2 > 0.99) and low limits of detection (0.09–0.19 mg kg–1) and quantitation (0.26–0.58 mg kg–1). The recoveries at three standard concentration levels ranged between 80.9% and 120%, with relative standard deviations below 12%. The expanded uncertainties determined for the five colourants in three food matrices were 8.2–19.4%. This method was applied to monitor five illegal colourants in imported and domestic beverages, candies, and sauces. None of the five colourants were found in any of the 510 samples. The method is suitable for quantitative analysis of five illegal colourants simultaneously in various foods and can be applied to improve current surveillance and inspection services.