Review of Determination Methods of Sudan Dyes in Food
Sudan dyes (most important of them are Sudan I, II, III and IV) are a family of compounds in the class of azo dyes that are used for different industrial and scientific applications (coloring of fuel, staining for microscopy, etc). Because of their low cost and wide availability, Sudan dyes are also attractive as food colorants. However, due to their carcinogenicity they are banned for food usage in most countries, including in the EU. Nevertheless, according to the European Union Rapid Alert System for Food and Feed reports there have been a large number of cases where Sudan dyes have been found in food. This has forced the European Commission to adopt a decision on emergency measures against Sudan dyes in food and calling the member states to organize testing of food products on the market.
Although concentration of Sudan I in 100-1000 mg/kg range is required to impact the color of chili products, commonly reported levels of Sudan dyes are in the low mg/kg range. Hence, accurate analysis of low levels of Sudan dyes in food is of huge importance.
Recently a review paper A review of analytical techniques for determination of Sudan I-IV dyes in food matrixes (Journal of Chromatography A, 2010, 1217, 2747–2757) was published by authors from UT Chair of Analytical Chemistry. 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 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 clean-up.
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.
Full text of the review cannot be posted here due to copyright restrictions, but those interested to have it are welcome to contact Ivo Leito (see our Contact page).