Sudan Dyes Contamination Analysis

Sudan dyes are a group of synthetic organic chemicals including Sudan I, II, III, IV and other Sudan dyes. They have similar chemical structure with aromatic compounds containing azo group. They have intensely orange-red and rich red color.

Figure 1. Chemical structure of Sudan dyes and related food products

Sudan dyes are generally used in commercial manufacturing as coloring substances in oils, plastics and waxes. Some of Sudan dyes can also be applied in drugs and cosmetics. They are easy to obtain with low cost.

One major source for Sudan dyes getting into the foods is through illegal addition. Recent years, there are more concerns associated with the adulterated use of Sudan dyes in foods. Sudan dyes are added into the food as a colorant. Sudan I has been adopted in various foods for coloring such as chili powder and curry pastes. Sudan IV is also a coloring matter that is not permitted in foods. However, there have been reports on the addition of Sudan IV in duck feeds to enhance the color of egg yolks. The addition of Sudan dyes into food products has been banned by many countries.

Sudan dyes can cause skin allergens through contact. The most serious health problem with it is the carcinogenicity. The International Agency for Research on Cancer (IARC) has classified Sudan I, III and IV as category 3 carcinogens. EU regulation has warned that Sudan I is a health hazard to human beings. There are more concerns recently on the potential genotoxic risks of Sudan dyes. It is suspected that Sudan I can cause genetic defects and cancer.

The use of Sudan dyes in foods as coloring matters is strictly prohibited in China and countries in European, Canada and Australia. The European Union requires to test Sudan I for all hot chili products imported to Europe. The European Union also announced that the limit of detection for the determination of Sudan I using high performance liquid chromatography is in the range of 0.5 - 1.0 ppm.

The procedure for the analysis of Sudan dyes in food products includes sample preparation and extraction, clean-ups, and detection/quantification. We control sample preparation factors and have extensive steps for sample clean-up step. We have expertise in sample preparation of a variety types of food matrices. The sample preparation has significant effect on the accuracy of the level measured in the food samples.

We offer accurate and validated analytical methods that have been widely applied in the determination of Sudan dyes in food samples to meet customers' needs.

High performance liquid chromatography (HPLC)

HPLC is generally used for the analysis of Sudan I in chili powder and crushed chili. It can also be applied for the testing of other Sudan dyes.

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS)

LC-MS/MS can be used for the analysis of Sudan I, II and other Sudan dyes. The limit of detection is typically at 10 ppb.

We also maintain high quality assurance for the analysis. The recovery of internal standard, the use of blanks and spikes is monitored for each batch of analysis.