Preparative separation of isomeric 2-(2-quinolinyl)-1H-indene-1,3(2H)-dione monosulfonic acids of the color additive D&C Yellow No. 10 (Quinoline Yellow) by pH-zone-refining counter-current chromatography

Preparative separation of quaternary ammonium alkaloids from Coptis chinensis Franch by pH-zone-refining counter-current chromatography

“…In addition, this method enables detection of samples by their pH, which is especially useful if the analyte has low ultraviolet absorbance [2,3,5]. It has been successfully used as a large-scale preparative technique for separating ionizable compounds which include alkaloids [6][7][8], synthetic colors [9,10], isomers [11][12][13], peptide derivatives [14,15], etc.…”

Preparative separation of quaternary ammonium alkaloids from Corydalis yanhusuo W. T. Wang by pH‐zone‐refining counter‐current chromatography

“…In addition, this method enables detection of samples by their pH, which is especially useful if the analyte has low ultraviolet absorbance [2,3,5]. It has been successfully used as a large-scale preparative technique for separating ionizable compounds which include alkaloids [6–8], synthetic colors [9, 10], isomers [11–13], peptide derivatives [14, 15], etc.…”

Separation of pyridine derivatives from synthetic mixtures by pH‐zone‐refining counter‐current chromatography

“…In addition, the method provides various special features by yielding highly concentrated fractions, concentrating minor impurities for detection, and allowing the separation to be monitored by the pH of the effluent when no chromophores are present [13][14]. In previous studies, this technique was applied to the separation of many natural products [15][16][17], peptide derivatives [18][19], synthetic colors [20][21][22][23], and isomeric compounds [21,[24][25]. The present paper reports the preparative separation of pyridine derivatives in high purity from synthetic mixtures by pH-zone-refining CCC.…”