Preparative separation of di- and trisulfonated components of Quinoline Yellow using affinity-ligand pH-zone-refining counter-current chromatography

Abstract

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 1.21 g of 6′,5-diSA and 1.69 g of 6′,8′,5-triSA, both of over 99% purity. A minor component, 8′,4-diSA, not previously reported was also obtained (4.8 mg 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 (0.55 g) in the 5 g 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 20.7 mg of 6′,4-diSA, not previously reported, and 111.8 mg 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.

Preparative separation of isoquinoline alkaloids from Stephania yunnanensis by pH-zone-refining counter-current chromatography

“…Compared to traditional CCC, it has many important advantages including an over 10-fold increase in sample loading capacity, high concentration of fractions, concentration of minor impurities, etc. In previous research, this method has been successfully applied to the analysis and separation of various natural and synthetic products, especially for alkaloids and organic acids [11][12][13][14][15][16]. So far, no report has been published on the use of CCC for the isolation and purification of isoquinoline alkaloids in S. yunnanensis.…”

Concentration and selective fractionation of an antihypertensive peptide from an alfalfa white proteins hydrolysate by mixed ion-exchange centrifugal partition chromatography

“…This method was highly productive and selective for the purification of organic molecules from many compound classes, but it cannot be applied to unprotected peptides due to their amphoteric nature. More recently, an improvement of the pH-zone refining process, called "affinity-ligand countercurrent chromatography", and closed to the ion-exchange process, was developed by Ma and Ito for the purification of unprotected peptide or di-and trisulfonated components of Quinoline Yellow using HSCCC devices [13][14][15]. In their approach, an ion-pairing reagent was added to the stationary phase in order to improve analyte extraction in the organic stationary phase.…”

Preparative separation and identification of novel subsidiary colors of the color additive D&C Red No. 33 (Acid Red 33) using spiral high-speed counter-current chromatography

“…Conventional HSCCC in both its standard elution mode and pH-zone-refining CCC elution mode [13] has been applied successfully to the preparative separation and/or purification of components from various synthetic dyes such as those of the xanthene [14–19], triphenylmethane [20], quinoline [21,22], azo [23–25], pyrene [26], and indigo [24] types. The technique has also been used for purifying dye intermediates [27] and reaction by-products [28] and for separating components of natural colorants [29–34].…”

“…Highly polar compounds, such as sulfonated dyes, partition mostly into the lower aqueous phase of commonly used organic/aqueous two-phase solvent systems. To facilitate partitioning of such compounds into the upper organic phase and thus their separation by HSCCC, a ligand (hydrophobic counterion) was added in previous studies [21,22,26]. Use of a ligand would not have been necessary if a more polar solvent system could have been used.…”