Determination of Sudan III, Sudan IV and Sudan Red 7B in Water by High Performance Liquid Chromatography after Mixing Extraction

A method is described for the determination of Sudan III, Sudan IV and Sudan Red 7B in river and seawaters. These dyes were extracted with hexane by mixing extraction from samples. The resulting materials were dried, dissolved in methanol and analyzed by high performance liquid chromatography with a variable-wavelength UV-VIS spectrophotometric detector. The separation of the dyes was possible using a LiChrosorb RP-18 column (25cm×4.0mm i.d.). The recoveries were 72.9-92.8% from river water and 94.6-98.1% from seawater, with the relative standard deviations below 4% (n=5) when 2μg of each dye was added to a 400-ml sample of water. The lower limits of determination were 4.4ng (0.55μg/l) for Sudan III, 5.3ng (0.66μg/l) for Sudan IV and 4.9ng (0.61μg/l) for Sudan Red 7B. This method allows simultaneous determination of the 3 dyes in water with simplicity, sufficients ensitivity and accuracy.