High Pressure Liquid Chromatographic Determination of Uncombined Intermediates in FD&C Red No. 2

Abstract

Abstract A high pressure liquid chromatographic (HPLC) method is presented for the separation and determination of uncombined intermediates in FD&C Red No. 2 (amaranth). Samples of FD&C Red No. 2 containing 0.1—0.3% naphthionic acid, 0.1—0.4% 2-naphthol-3,6-disulfonic acid, 0.3—1.0% 2-naphthol-6,8-disulfonic acid, and 2-naphthol-3,6,8-trisulfonic acid were prepared and analyzed by HPLC. Recoveries ranged between 92 and 101%. Twenty samples of FD&C Red No. 2 were analyzed by the conventional column chromatographic method and the HPLC method. The HPLC method was superior, since it separated all the above intermediates from each other and from FD&C Red No. 2 in one quarter the time required by the conventional column chromatographic method which did not separate the individual intermediates.