Establishment of an immunoaffinity chromatography for simultaneously selective extraction of Sudan I, II, III and IV from food samples

The establishment of an immunoaffinity chromatography (IAC) for simultaneously selective extraction of four illegal colorants Sudan dyes (Sudan I, II, II and IV) from food samples was described. The IAC column was constructed by covalently coupling monoclonal antibody (mAb) against Sudan I to CNBr-activated Sepharose 4B and packed into a common solid phase extraction (SPE) cartridge. It was observed that IAC column was able to separately capture Sudan I, II, III and IV with maximum capacity of 295, 156, 184 and 173 ng, respectively. The extraction conditions including loading, washing and eluting solutions were carefully optimized. Under optimal conditions, the extraction recoveries of the IAC column for Sudan I–IV at two different spiked concentrations were within 95.3–106.9%. After 50 times repeated usage, 64% of the maximum capacity was still remained. Six food samples randomly collected from local supermarket without spiking Sudan dyes were extracted with IAC column and detected by high performance liquid chromatography (HPLC). It was found that there was no detectable Sudan II, III and IV in all six food samples, but Sudan I with the content of 2.7–134.5 ng g−1 was detected in three food samples. To further verify the extraction efficiency, other three negative samples were spiked with Sudan I–IV at the concentrations of 20 ng g−1 and 50 ng g−1, which were then extracted with IAC column. The extraction recoveries and relative standard deviation (RSD) were 68.6–96.0% and 4.8–15.2%, respectively, demonstrating the feasibility of the prepared IAC column for Sudan dyes extraction.