A review of analytical techniques for determination of Sudan I–IV dyes in food matrixes

Sudan dyes are a family of lipophilic azo dyes, extensively used in industrial and scientific applications but banned for use as food colorants due to their carcinogenicity. Due to the continuing illicit use of Sudan dyes as food colorants their determination in different food matrices – especially in different chilli and tomato sauces and related products – has during the recent years received increasing attention all over the world. This paper critically reviews the published determination methods of Sudan I–IV dyes. LC–UV–vis and LC–MS are the dominating methods for analysis of Sudan I–IV dyes. Sudan dyes are usually found in food at mg kg−1 levels at which it may be necessary to use a preconcentration step in order to attain the desired detection limits. Liquid–solid extraction is the dominating sample preparation procedure. In recent years it has been supplemented by ultrasonic-assisted extraction and pressurized liquid extraction. Various solid phase extraction types have been used for sample cleanup. The large majority of works use conventional C18 columns and conventional LC eluents. Traditionally the UV–vis absorbance detection has been the most frequently used. In the recent years MS detection is applied more and more often as it offers more reliable identification possibilities.