Purification of Some Water Soluble Azo Dyes by High-Speed Countercurrent Chromatography

Freeman, Harold S.; Hao, Zengzhou; McIntosh, Stanley A.; Mills, Kimberly P.

doi:10.1080/01483919808068327

Cited by 14 publications

(1 citation statement)

References 12 publications

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“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Weisz

Ridge

Mazzola

et al. 2015

Journal of Chromatography A

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Three low-level subsidiary color impurities (A, B, and C) often present in batches of the color additive D&C Red No. 33 (R33, Acid Red 33, Colour Index No. 17200) were separated from a portion of R33 by spiral high-speed counter-current chromatography (HSCCC). The separation involved use of a very polar solvent system, 1-BuOH/5 mM aq. (NH4)2SO4. Addition of ammonium sulfate to the lower phase forced partition of the components into the upper phase, thereby eliminating the need to add a hydrophobic counterion as was previously required for separations of components from sulfonated dyes. The very polar solvent system used would not have been retained in a conventional multi-layer coil HSCCC instrument, but the spiral configuration enabled retention of the stationary phase, and thus, the separation was possible. A 1 g portion of R33 enriched in A, B, and C was separated using the upper phase of the solvent system as the mobile phase. The retention of the stationary phase was 38.1%, and the separation resulted in 4.8 mg of A of >90% purity, 18.3 mg of B of >85% purity, and 91 mg of C of 65–72% purity. A second separation of a portion of the C mixture resulted in 7 mg of C of >94% purity. The separated impurities were identified by high-resolution mass spectrometry and NMR spectroscopic techniques as follows: 5-amino-3-biphenyl-3-ylazo-4-hydroxy-naphthalene-2,7-disulfonic acid, A; 5-amino-4-hydroxy-6-phenyl-3-phenylazo-naphthalene-2,7-disulfonic acid, B; and 5-amino-4-hydroxy-3,6-bis-phenylazo-naphthalene-2,7-disulfonic acid, C. The isomers A and B are compounds reported for the first time. Application of the spiral HSCCC method resulted in the additional benefit of yielding 930 mg of the main component of R33, 5-amino-4-hydroxy-3-phenylazo-naphthalene-2,7-disulfonic acid, of >97% purity.

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