HPLC Determination of Sudan Dyes in Chilli Products with Purification by Gel Permeation Chromatography

Appropriate amount of the chilli product sample was extracted ultrasonically with the mixture of cyclohexane and acetone (3+1). After centrifugation, the supernatants were taken and evaporated to near dryness. The residue was dissolved and made up to 10 mL with the mixture of cyclohexane and ethylacetate (1+1), which is also the mixture in gel permeation chromatography (GPC). Eluates flowed out during the interval of 22-30 min were collected, and evaporated to dryness at 40 ℃ by N2-blowing. The residue was dissolved and made up to 1 mL with acetonitrile-water (8+2) solution. Waters Symmetry C18 column was used for separation with mixtures of water and acetonitrile in various proportions used as mobile phase in gradient elution. Detections were made with PDA at 478 nm for Sudan Ⅰ and at 520 nm for Sudan Ⅱ, Ⅲ and Ⅳ. Linearity ranges for the 4 dyes were found same between 0.1 to 5 mg·L-1. Detection limits of the 4 dyes found in chilli oil were 0.02 mg·kg-1, and in chilli sauce and chilli powder were same as 0.005 mg·kg-1. Tests for recovery were made by standard addition method, giving values of recovery in the range of 79.5%-93.8%, with RSD′s (n=6) in the range of 1.9%-8.3%.