A new liquid–liquid extraction method for determination of 6 azo-dyes in chilli products by high-performance liquid chromatography

A liquid–liquid extraction method was developed for purifying and enriching the sample of 6 azo-dyes (including Para red, Sudan red G, Sudan I, Sudan II, Sudan III and Sudan IV) by formic acid and chloroform. The results indicated that formic acid can facilitate the solution of fat-soluble azo-dyes, which was helpful for the separation of the fat-soluble interferences from the samples. The extracting conditions of 6 azo-dyes were also optimised. And the proposed extraction method was evaluated by the determination of 6 azo-dyes in chilli products. The mean recoveries of 6 azo-dyes were from 94.1% to 99.2% for chilli powder and from 94.2% to 98.6% for chilli spice. The CCα and CCβ obtained for 6 azo-dyes were in the range of 1.7–2.1 and 2.8–3.4 μg/kg for chilli spice and chilli powder. The inexpensive and simple method was acceptable for routine monitoring 6 azo-dyes in chilli products.