Preparative separation of di- and trisulfonated components of Quinoline Yellow using affinity-ligand pH-zone-refining counter-current chromatography.
Four positionally isomeric 2-(2-quinolinyl)-1H-indene-1,3(2H)-dionedisulfonic acids (SA) and one triSA, components of the color additive Quinoline Yellow (QY, Color Index No. 47005), were isolated from the dye mixture by affinity-ligand pH-zone-refining counter-current chromatography (CCC) through complementary use of ion-exchange and ion-pair reagents as the ligand. The added ligands facilitated the partitioning of the very polar polysulfonated components into the organic stationary phase of the two-phase solvent systems that consisted of isoamyl alcohol-methyl tert-butyl ether-acetonitrile-water (3:5:1:7), (3:4:1:7) or (3:1:1:5). Thus, separation of a 5-g portion of QY using sulfuric acid as the retainer and dodecylamine as the ligand (an ion-exchange reagent, 20% in the stationary phase), resulted in 1.21g of 6',5-diSA and 1.69g of 6',8',5-triSA, both of over 99% purity. A minor component, 8',4-diSA, not previously reported was also obtained (4.8mg of over 94% purity) through a similar separation of a different batch of QY using hydrochloric acid as the retainer and 10% dodecylamine as the ligand in the stationary phase. Two components that co-eluted (0.55g) in the 5g separation were separated when trifluoroacetic acid was used as the retainer and tetrabutylammonium hydroxide (an ion-pair reagent) as the ligand. The separation resulted in 20.7mg of 6',4-diSA, not previously reported, and 111.8mg of 8',5-diSA, both of over 98% purity. The isolated compounds were characterized by high-resolution mass spectrometry and proton nuclear magnetic resonance with correlated spectroscopy assignments.
Weisz
Adrian
A
Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park, MD 20740, USA. adrian.weisz@fda.hhs.gov
Mazzola
Eugene P
EP
Ito
Yoichiro
Y
D004396:Coloring Agents / Q000737:chemistry / Q000302:isolation & purification*; D003377:Countercurrent Distribution / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D008024:Ligands; D013058:Mass Spectrometry; D019906:Nuclear Magnetic Resonance, Biomolecular; D011804:Quinolines / Q000737:chemistry / Q000302:isolation & purification*; D013451:Sulfonic Acids / Q000737:chemistry / Q000302:isolation & purification*
D004396:Coloring Agents; D008024:Ligands; D011804:Quinolines; D013451:Sulfonic Acids; C019303:quinoline yellow