Color can increase the sensory quality of food, which is also an important evaluating indicator for consumer to judge the freshness of the products. As one category of the essential additives in food industry, colorants are usually classified as either natural or synthetic. Synthetic colorants generally have a higher tinctorial strength than natural colorants; what's more, synthetic colorants are usually water-soluble, relatively stable and not easily destroyed during the food processing process [1] and [2]. These features, together with their lower price, make synthetic colorants more widely used all over the world today. However, with the attention to toxicological studies, the potential risks of many synthetic azo colorants to human health are found and concerned. Former researches have found that amaranth starting at a certain concentration can induce dose-related DNA damage in the mouse colon after oral administration [3] and [4]. In addition to the genotoxicity, some synthetic colorants can also cause allergic or asthmatic reaction for sensitive people, such as frequent headaches and children's hyperactivity [5], [6] and [7]. To prevent the abuse of synthetic colorants, the permissible type and usage of synthetic colorants were strictly regulated in many countries. In China, the use range and dosage of synthetic colorants in foodstuffs were also authorized by the Ministry of Health (GB 2760-2011) [8]. Consequently, it is necessary to develop sensitive, accurate and fast methods for the determination of synthetic colorants in foodstuffs.