For the purpose of checking the quality and eliminating the contact allergenic property of Quinoline Yellow WS, analyses and purification of the dye were carried out as follows.
(1) Sulfonated sites of six main derivatives in commercial dyes were clarified by field desorption mass spectrometory, 13C-NMR and 400MHz1H-NMR. Samples commercially available from Japan (as Yellow No. 203) and from GFR (as E 104) were analyzed by HPLC. The following compounds were determined as main components: 2-(2′-quinolyl)-1, 3-indandion-5, 6′, 8′-trisulfonic acid, 2-(2′-quinolyl)-1, 3-indandion-5, 6′-disulfonic acid, 2-(2′-quinolyl)-1, 3-indandion-5, 8′-disulfonic acid and/or 2-(2′quinolyl)-1, 3-indandion-6′-methyl-5, 8′-disulfonic acid. Their total colors were 39.7-70.9%. Dyes of USA (as D & C Yellow No. 10), on the other hand, mainly contained 2-(2′-quinolyl)-1, 3-indandion-6′-sulfonic acid and 2-(2′-quinolyl)-1, 3-indandion-8′-sulfonic acid, and their total colors were 82.0-88.0%.
(2) Analysis by HPLC indicated that commercial dyes contained 0.11-170ppm Quinoline Yellow SS, which showed contact sensitivity at the concentration of about 0.1ppm.
(3) During the purifying procedure of the commercial dye, Quinoline Yellow SS decreased below 0.01ppm, and total color increased to above 90%.
(4) Quinoline Yellow SS was scarcely produced from Quinoline Yellow WS by desulfonation in diluted acids.
