title: A sensitive and selective direct competitive enzyme-linked immunosorbent assay for fast detection of Sudan I in food samples.
abstract: BACKGROUND
  Sudan I, a synthetic azo dye, is considered to be a genotoxic carcinogen and is prohibited in foodstuffs for any purpose at any level worldwide. In this study, a sensitive and specific direct competitive enzyme-linked immunosorbent assay (dc-ELISA) for fast detection of Sudan I in food samples was developed for the first time. The monoclonal antibody against Sudan I was used as capture protein, while horseradish peroxidase labeled Sudan I conjugate prepared by the periodate method via ovalbumin (OVA) as a bridge was used as enzyme tracer.
  
  
  RESULTS
  The standard curve of dc-ELISA for Sudan I was constructed in the range 0.1-100 ng mL⁻¹ and the assay time was within 80 min. Sensitivity was 2.6 ng mL⁻¹ and the limit of detection was 0.08 ng mL⁻¹. Cross-reactivity values of the assay with Sudan II, III and IV were 5.78%, 1.72% and 0.64%; no cross-reactivity was found with six other edible colorants. The assay was tolerated to 30% of methanol and 10% of acetonitrile without significant loss of IC₅₀. Recoveries of spiked Sudan I in five different samples including chilli powder, tomato sauce, hotpot seasoning and chilli sauce I and II were within 88.4-113.2% and the intra-assay relative standard deviation was less than 14%. The dc-ELISA was confirmed by conventional high-performance liquid chromatography and the correlation coefficient of the two methods was 0.9902.
  
  
  CONCLUSIONS
  The proposed dc-ELISA method provides an alternative method for sensitive, specific and fast determination of Sudan I in food samples.
authors: College of Chemistry, Sichuan University, Chengdu 610064, China.
authors: Yuzhen
authors: Y
authors: Wang
authors: Hong
authors: H
authors: Yang
authors: Bin
authors: B
authors: Wang
authors: Anping
authors: A
authors: Deng
mesh_terms: D000911:Antibodies, Monoclonal; D001391:Azo Compounds / Q000032:analysis*; D002273:Carcinogens / Q000032:analysis*; D004396:Coloring Agents / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005506:Food Contamination / Q000032:analysis*; D007202:Indicators and Reagents; D009153:Mutagens / Q000032:analysis*
chemical_list: D000911:Antibodies, Monoclonal; D001391:Azo Compounds; D002273:Carcinogens; D004396:Coloring Agents; D007202:Indicators and Reagents; D009153:Mutagens; C033003:sudan red