High Performance Liquid Chromatographic Separation and Spectral Characterization of the Pigments in Turmeric and Annatto

High performance liquid chromatographic separations for the determination of the pigments in the food colorants, annatto and turmeric, were developed. Chromatographic analysis time for the isocratic system was 10 min and 22 min for the gradient system. The isocratic separation employed a 25 cm × 4.6 mm i.d. Zorbax ODS column with a 58/42 (v/v) mixture of water/tetrahydrofuran, THF, at 1 mL/min. A gradient water/THF system using the same components was also developed to improve the resolution between the curcuminoids. Sample preparation consists of dilution and filtration of the extracts. The three major pigments in turmeric, identified from visible and fluorescence stop flow spectra, were curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Absorbance, excitation and emission maxima for the three curcuminoids plus the carotenoids, bixin and norbixin, were determined.