Detection of Sudan Dyes in Red Chilli Powder by Thin Layer Chromatography

Abstract

Sudan I, II, III & IV are suspected genotoxic carcinogens and reports have shown the adulteration of chilli and chilli containing products with these azo dyes in recent past. In this study, a Simple Thin Layer Chromatographic method is described for the qualitative detection of Sudan-III & IV in Red chilli powder. The study includes extraction of sample, preparation of Thin Layer Chromatography (TLC) plates and Separation cum detection of dyes on TLC plates. The dyes were extracted with solvent Acetonitrile. Sample extracts were filtered and analyzed by simple thin layer chromatography in benzene, hexane and acetic acid solvent system. The chromatograms of sample, standard and spiked samples were evaluated in term of Rf and relative Rf values. The relative Rf values of four samples analysed, relative to the two standards of Sudan (III- S2 and IV S1) were less than one (P1-0.13,0.25; P2-0.1 9,0.35; P3-0.30,0.35; P4-0.15,0.26 and P5-0.20,0.38), confirming the absence of Sudan III and IV in these samples. The efficiency of the method was checked by internal standard method, in which pure sample was spiked by known weight of standard dye. The relative Rf values of spiked sample was almost equal to one (b1-0.93, b2-0.80). Limit of detection (5 mg/kg) was calculated on the basis of visual evaluation of spots (i.e. spot visible or not at given concentration of standard dye) under normal light without any derivetization. The chilli samples analysed though varied in color intensity, but none of them was found to contain Sudan III or IV.