Sudan I, Sudan II, Sudan III and Sudan IV (Scarlet Red) are synthetic industrial azo-dyes used in waxes, plastics, oils and polishes. Sudan dyes sometimes are added to foods such as chili powder to mimic, intensify and prolong the appearance of natural red hues. The International Agency for Research on Cancer (IARC) classifies Sudan dyes as Class 3 carcinogens and, therefore, it is illegal to use them as food additives, according to the FDA and EU. (2,3) Since 2003, European nations have required random product testing and testing of suspected adulterated products, and Sudan dyes recently have been found in food products in some European countries. More than six hundred products containing Sudan dyes have been recalled in the UK—the largest food recall in British history. (1)

Laboratories performing analysis of Sudan dyes are not required to follow defined methods. However, the EU has set detection limits for these dyes at 0.5 - 1 mg/kg, and has stated that any foods or food ingredients found to contain more than the established limit should be withdrawn from the market. (1)

HPLC MS of Sudan I, Sudan II, Sudan III and Sudan IV

Sudan dyes were prepared as in Simple HPLC Analysis for Sudan Dyes and analyzed using an update of the method described there. Ten microliters of a 1ppm solution were injected, via a Waters 717plus autosampler. A 1525 binary pump was used to provide an isocratic flow of 0.15 mL/minute. The mobile phase was acetonitrile: methanol (70:30, v/v), each containing 0.1% formic acid. A Waters ZMD mass spectrometer was used in positive electrospray mode, 3.5 kVolts capillary voltage, 10 volts cone voltage, 150°C source temperature and 200°C desolvation temperature. An Ultra Aqueous C18 column (150 x 4.6mm, cat.# 9178565) and positive electrospray mass spectrometry were used to identify the four Sudan dyes in less than ten minutes. The cone voltage was optimized to discourage in-source fragmentation. Extracted ion chromatograms and mass spectra for the Sudan dyes are shown in Figure 1 and Figure 2.

LCMS DATA Extracted m/z values for [M+H]+ of Sudan I, II, III, IV
This figure shows the extracted ion chromatograms for Sudan I (m/z 249), Sudan II (m/z 277), Sudan III (m/z 353) and Sudan IV (m/z 381). Sudan Dyes Spectra This figure shows the mass spectra for Sudan I (m/z 249), Sudan II (m/z 277), Sudan III (m/z 353) and Sudan IV (m/z 381). These were produced by manually combining spectra and subtracting background.

References

1. www.ift.org
2. Commission Decision of 20 June 2003 on emergency measures regarding hot chilli and hot chilli products, notified under document number C(2003) 1970, (2003/460/EC), OJ L. 154/114, 21.6.2003.
3. Implementation of Commission Decision 2003/460/EC of the 21st January 2004.

Other Sources

1. Journal of Chromatography A: 1042, 2004, 123-130
2. Journal of Chromatography A: 1058, 2004, 127-135