Abstract:

Humic acid-bonded silica was prepared and used as solid-phase

extraction material for the pretreatment of Sudan Red dyes in hot chili

products, which was followed by high performance liquid chromatographic

determination. This sorbent exhibits an excellent adsorption capacity for

Sudan Red dyes. A sample was first extracted with n-hexane. Then the

extract was cleaned up by humic acid-bonded silica cartridge and eluted

with ethanol/dichloromethane (3∶7, v/v). Some interferences in hot chili

products such as natural pigments and oil were removed by washing step.

Good linearities were achieved in the range from 0.05 to 5 mg/L for four

Sudan dyes, with linear coefficient r2 values above 0.999. The limits of

detection (LOD) in chili powder and chili oil were from 19.8 to 28.8 ng/g

and 7.9 to 11.5 ng/g， respectively. Excellent method reproducibility was

found by intra- and inter-day precisions (the relative standard

deviations less than 9.1% and 8.8%, respectively). Recoveries for them in

the real samples were between 82.6% and 94.0%. The proposed method is

proved to be simple, rapid, and sensitive in the regular analysis of

Sudan Red Ⅰ, Ⅱ, Ⅲ and Ⅳ in foods.

Key words: high performance liquid chromatography (HPLC), solid-phase extraction (SPE), Sudan Red dyes , humic acid