Abstract:

A HPLC coupled with diode-array detector (HPLC-DAD) method for the successful separation and determination of 6 synthetic pigments (tartrazine, amaranth, ponceau 4R, sunset yellow, allura red, and red 2G) was developed. Samples were extracted using a system consisting of 4 mol/L carbamide solution and methanol (1:1, V/V) and cleaned up on a solid phase extraction column using polyamide powder with the mesh from 100 to 200 mesh with a mixture of 25% ammonia and methanol (1:9, V/V) as the eluent. The extracts were adjusted to pH 5 － 6 and hold in 60 ℃ water bath for 20 min prior to polyamide adsorption. The chromatographic separation was achieved on an XDB-C18 column using a mobile phase consisting of methanol and 0.1 mol/L sodium acetate by gradient elution. The 6 synthetic pigments were detected with a diode-array detector whose wavelength was set according to the following procedure: 0－7 min, 440nm; and 7－35 min, 520 nm. The detection limits of tartrazine, amaranth, ponceau 4R, sunset yellow, red 2G and allura red were 0.03, 0.03, 0.03, 0.03, 0.04 and 50 mg/kg, respectively. The RSDs ranged from 0.47% (ponceau 4R) to 4.82% (sunset yellow), and the recoveries were in the range from 95.67% (allura red) to 99.55% (tartrazine).

Key words: solid phase extraction, HPLC-DAD, synthetic pigment, simultaneous determination, ham