LC-MS/MS Determination of 8 Sudan Dyes in Concentrated Carrot Juice

LC-MS/MS was applied to the determination of 8 Sudan dyes, i.e., Sudan orange G, Sudan red G, Sudan red 7B, Sudan yellow, Sudan red Ⅰ, Sudan red Ⅱ, Sudan red Ⅲ and Sudan red Ⅳ, in concentrated carrot juice. The sample was extracted by n-hexane, concentrated to near dryness in a rotary evaporator at 39 ℃, and evaporated to dryness by N2-blowing. The residue was dissolved with 1 mL of a mixed solvent of methanol and 0.1% (φ) formic acid (1+1). Hypersil GOLD (50 mm×2.1 mm, 1.9 μm) column was used as chromatographic column, and mixtures of methanol and 0.1% (φ) formic acid in various ratios were used as mobile phase in the gradient elution; positive electrospray ionization as well as multiple reaction monitoring mode was used in the detection. Linear relationships between values of peak area and mass concentration of 8 Sudan dyes were kept in the same range of 30-100 μg·L-1, with lower limits of determination (10S/N) in the range of 5-30 μg·kg-1. Tests for recovery were made by addition of standard solutions at 3 different concentration levels, values of recovery found were in the range of 72.0%-96.0%, with values of RSD′s (n=6) in the range of 6.2%-9.6%.