Thesis (M.Sc.)--Chulalongkorn University, 2009

A rapid, accurate and precise method has been developed for the determination of Sudan I-IV in chili products using on-line solid phase extraction and LC-MS. Chili products were extracted with acetone and the analytes were cleaned up and enriched on an SPE column (C[subscript 18], 15-40 µm) through on-line SPE. Chromatographic separation was performed on a C[subscript 18] analytical column (2.1x150 mm, 3 mum) with gradient elution programming of 0.1% formic acid in water and 0.1% formic acid in acetonitrile. All four Sudan dyes were separated in less than 8 min. Using in-house validation data, a linearity coefficient of determination (R[superscript 2]) of more than 0.9997 was obtained. The limits of detection (LOD) and limits of quantitation (LOQ) were the same for Sudan I, II and IV and those values were 0.03 and 0.05 mg kg[superscript -1], respectively, and 0.04 and 0.1 mg kg[superscript -1] for Sudan III. The intra- and inter-day recoveries of the four Sudan dyes in chili powder were between 90.14-101.65% and 90.22-102.02%, respectively, with relative standard deviation (RSD) between 0.014-0.164% and 0.011-0.202%, respectively. The proposed method was used to detect Sudan I-IV in food samples such as chili sauce, roasted chili paste and dried chili. The results showed that Sudan I-IV were not found in real samples. To verify, real samples were spiked at 3 levels of standard Sudan dyes. The recoveries were found to be more than 90%. Therefore, the proposed method which is rapid, sensitive, less sample and solvent consumption could be applicable for the determination of Sudan I-IV in chili products.