[Preparation of HPLC test solutions for organic impurities in aluminum lakes of food red no. 40 (allura red AC) and food yellow no. 5 (sunset yellow FCF)].

The HPLC determination of organic impurities in Food Red No. 40 aluminum lakes (R-40Als) as directed by Japan's Specifications and Standards for Food Additives, 7th Ed. (JSFA-VII), has problems, such as reproducibility and low recovery. ICP analyses suggested that the problem was caused by the aluminum in the test solution. In the improved method for preparation of the test solution, aluminum was precipitated as a hydroxide gel by boiling with 1% aqueous ammonia. After centrifugation, the supernatant was used for the HPLC analysis of the organic impurities in the lakes. Recoveries of organic impurities were more than 85% from R-40Al spiked at the 0.1 and 1.0% levels of R-40. The proposed method was also adapted for Food Yellow No. 5 aluminum lakes.