PH-zone-refining

Fig. 3.117. Separation of 6SA and 8SA from a certified lot of D C Yellow No. 10 by pH-zone-refining CCC. (a) HPLC analysis of colour additive and (b) HPLC analyses of the separated components. Reprinted with permission from A. Weisz et al. [172].

Fig. 3.119. Separation of the components of Food Colour Red No. 106 by pH-zone-refining CCC. For conditions see text. Reprinted with permission from H. Oka et al. [173],...

A. Weisz, E. P. Mazzola, J.E. Matusik and Y. Ito, Preparative separation of isomeric 2-(2-quinolinyl)-lH-indene-l,3(2H)-dione monosulfonic acids (6SA and 8SA) of the color additive D C Yellow No. 10 (Quinoline Yellow) by pH-zone refining counter-current chromatography./. Chromatogr.A, 923 (2001) 87-96. 

H. Oka, M. Suzuki, K.-I. Harada, M. Iwaya, K. Fuii, T. Goto, Y. Ito, H. Matsumoto andY. Ito, Purification of Food Color Red No. 106 (acid red) using pH-zone-refining counter-current chromatography. J. Chromatogr.A, 946 (2002) 157-162. 

For the given systems (ionizable selectors and solutes), a modified form of CPC was usually more favorable The so-called pH-zone-refining CPC mode, which is a kind of displacement type of chromatography. In this mode, the column is filled with the acidified stationary phase (e.g., using TFA as retainer), then injection of the sample takes place before the rotor is switched on and elution is started with a basic mobile phase (e.g., using ammonia as displacer in the aqueous mobile phase). Apparent pH and enantiomeric composition were determined for every fraction. It appeared that the enantiomers eluted in refined... 

Fig. 2 pH-Zone-refining CCC separation of 2 g ( ) DNB-leucine using the same HSCCC centrifuge with a CS (A/ -dodecanoyl-L-proline-3,5-dimethylanilide) in the stationary phase. 

Standard pH-zone-refining CCC was applied to the separation of pure components, sometimes multigram quantities, from various halogenated fluorescein (F) dyes such as 4,5,6,7-tetrachloroF, D C Orange No. 5 (mainly 4, 5 -dibromoF), D C Red No. 22 (Eosin Y, mainly the disodium salt of 2, 4, 5, 7 -tetrabromoF), D C Orange No. 10 (mainly 4, 5 -di-iodoF), FD C Red No. 3 (Erythrosine, mainly the... 

Fig. 1 Separation by affinity-ligand pH-zone-refining CCC in the ion-exchange mode of the main components from a sample of D C Yellow No. 10 (Quinoline Yellow, Cl 47005). (a) HPLC analysis of the original mixture (b) pH-zone-refining CCC elution profile and HPLC analyses of the combined fractions 81-103 and 114-138, respectively. For experimental conditions, see text and Ref. 9.

A. Weisz, A. L. Scher, K. Shinomiya, H. M. Fales, and Y. Ito, A new preparative-scale purification technique pH-Zone-refining countercurrent chromatography, J. Am Chem Soc 116 704-708 (1994). 

A. Weisz, Separation and purification of dyes by conventional high-speed countercurrent chromatography and pH-zone-refining countercurrent chromatography, in High-Speed Counter-current Chromatography (Y. Ito and W. D. Conway, eds.), John Wiley Sons, New York, 1996, pp. 337-384. 

Enrichment Using pH-Zone Refining Technique as Preconcentration Method of inorganic Anaiysis for Subsequent Determination... 

Even if sufficient sample size, in volume, may not be available, enrichment techniques that concentrate trace metals in microliter samples are sometimes quite useful because modern instrumental detection systems such as AAS, ICP-AES, ICP-MS, etc. do not need a large sample size. Moreover, if trace metals that have been separated from their major substances can be concentrated in an extremely small area of the polytetrafluoroethylene (PTFE) tube in HSCCC, this would be an ideal flow-injection analysis system for determination of inorganics. From this point of view, the recently developed pH-zone refining technique has great potential for enrichment, especially for instrumental inorganic trace analysis. 

In the pH-zone refining technique, a basic organic solution containing a complex-forming reagent, such as... 

Figure 4 shows the typical concentration results for a 10-ppm solution of cadmium, magnesium, and zinc. The injected sample solution contained 50 pg of each in 5 mL of 0.1 M tartaric acid solution, adjusted to pH to 9.25. The mobile phase was pumped at a flow rate of 0.05 mL/min. Rotational speed was 950 rpm. The eluent was collected every 2 min (0.1-mL fractions). The fractions were diluted 1 10 with water, and the emission intensity for each element was measured by plasma atomic emission spectrometer. The emission intensities for each element were increased 20-fold compared with the original sample solution. The results of this study demonstrated the high-performance capabilities of the pH-zone refining technique. Trace elements in the sample solution could be successfully concentrated into a small volume, almost under 0.1 mL with an enormous level of enrichment. 

E. Kitazume, N. Sato, and Y. Ito, A new preconcentration-detection method for trace metals by pH-zone-refining countercurrent chromatography, 1995 Pittsburgh Conference and Exposition on Analytical Chemistry and Applied Spectroscopy, 1995. 

Table 2 Peptide samples and solvent systems for pH zone-refining CCC...

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