Cellulose tribenzoate

Polysaccharides Chiralcel OB Cellulose tribenzoate coated on silica gel [19] Daicel... 

Rimbock et al.125 prepared microcrystalline cellulose tribenzoate powders and Francotte et al.126 128 prepared spherical beads of cellulose tribenzoate derivatives they found that these derivatives are useful CSPs with a high loading capacity. 

FIGURE 10.14 Single-component experimental isotherms foriJ- and 5-1-indanol on cellulose tribenzoate fitted to three different models. The inset shows the low-concentration data. (Reproduced from Zhou, D., Chem. Eng. Sci., 58, 3257, 2003. With permission from Elsevier.)... 

Cellulose triacetate Cellulose tribenzoate Cellulose mew-methylbcnzoate Cellulose para-methylbenzoate Cellulose phenylcarbamate... 

The effect of substituents on the phenyl groups of cellulose tribenzoate has been studied [17]. Cellulose triphenylcarbamate derivatives are the most thoroughly investigated polysaccharide phases with respect to chiral resolution and its... 

CSPs (CTA-I and CTA-II) have inverse selectivity for Troger s base and trans-1,2-diphenyloxirane racemates. These characteristics of CTA CSPs are responsible for good chiral resolution of small cychc carbonyl compounds [42]. In 2001 Aboul-Enein and Ah [63] observed the reversed order of elution of nebivolol on a Chiralpak AD column when ethanol and 2-propanol were used separately as the mobile phases. Table 1 presents selectivity data for the polysaccharide-based CSPs. Okamoto et al. [42] observed that the introduction of a methyl group at the para position of cellulose tribenzoate results in a dramatic shift of the structural selectivity toward aromatic compounds with larger skeletons, and its selectivity was rather similar to that of cellulose tricinnamate. 

FIGURE 10 Chromatograms of enantiomeric resolution on cellulose tribenzoate CSPs. (a) ( )-//ireo-Methylphenidate on Chiralcel OB CSP, with hexane-ethanol-methanol-trifluoroacetic acid (480 9.75 9.75 0.5, v/v/v/v) as the mobile phase containing 0.2 mM benzoic acid, (b) ( H/ireo-methylphenidate on Chiralcel OB CSP, with hexane-ethanol-methanol-trifluoroacetic acid (480 9.75 9.75 0.5, v/v/v/v) as the mobile phase containing 0.2 mM phenol, (c) Ic aromatase inhibitor on Chiralcel OJ-R CSP, with acetonitrile-water (50 50, v/v) as the mobile phase, (d) lie aromatase inhibitor on Chiralcel OJ-R CSP, with acetonitrile-water (50 50, v/v) as the mobile phase. For structures of Ic and lie aromatase inhibitors, see later (Fig. 18). (From Refs. 98, 100.)... 

Later, Wainer et al. [62,97] observed that the increase in the n basicity of the solute (substituting a phenyl group for hydrogen) resulted in improved chiral resolution of amides on cellulose tribenzoate (OB CSP) [97], while for certain aromatic alcohols resolution was decreased when the n basicity on a Chiralcel OB column was increased [62],... 

Non-aromatic chiral compounds are also resolved on the polysaccharide-based CSPs. Several non-aromatic compounds resolved on cellulose tribenzoate (OB) are shown in Figure 15.83 The detection by a UV detector is often difficult and an RI detector is more useful to detect the enantiomer peaks. 

Okamoto, Y., Aburatani, R., and Hatada, K. (1987) Cellulose tribenzoate derivatives as chiral stationary phases for high-performance liquid chromatography, J. Chromatogr. 389, 95-102. 

The resolution of 3,4-dihydro-2/f-l-benzothiopyran-4-one 1-oxide has been achieved by capillary electrophoresis using heptakis-6-sulfato-/3-cyclodextrin or, better, its 2,3-diacetyl derivative as the chiral selector the i -sulfoxide migrated before the A-enantiomer <2001JSS766>. It has also been noted that (R)-thiochroman 1-oxide is eluted before the (d )-enantiomer from a Chiralcel cellulose tribenzoate column <2001TA1551> and a Daicel Chiralpak AD-H column using hexane/APrOH 90 10 has been used to resolve the (3.y,l. R) 249 and (3/ ,l A) 250 enantiomers of the substituted tetrahydrothiopyran-4-one <20050BC84>. 

In a broad survey of various analytes about 80 of the compounds tested could be separated on the following four CSPs amylose tris(3,5-dimethylphenyl carbamate) (commercialized as Chiralpak AD), amylose tris[(S)-a-methylbenzyl carbamate] (Chi-ralpak AS), cellulose tris(3,5-dimethylphenyl carbamate) (Chiralcel OD), and cellulose tris(4-methyIbenzoate) (Chiralcel OJ), all coated onto the surface of macroporous y-aminopropyl silica. These columns behave excellently in non-aqueous HPLC mode, but they seem to be also well suitable for SFC separations. Other less widely used, but also commercially available polysaccharide-derived CSPs, e.g. cellulose triacetate, cellulose tribenzoate, and cellulose tricinnamate, or cellulose tris(phenylcarbamate), cellulose tris(4-chlorophenylcarbamate), cellulose tris(4-methylphenylcarbamate) selectors... 

Figure 3.31 Distribution of the equilibrium constants of adsorption calculated by means of the biToth model for 1-indanol on cellulose tribenzoate. The arrows indicate the equilibrium constants derived from the competitive bi-Langmuir isotherm. Reproduced with permission from A. Felinger, D. Zhou, G. Guiochon,. Chromatogr. A, 1005 (2003) 35.

Figure 3.40 Illustration of the method of isotherm measurements by computation of elution profiles. R-l-indanol on cellulose tribenzoate chiral stationary phase. Mobile phase, n-hexane and 2-propanol (92.5 7.5, v/v). (Left) Calculated (using the bi-Langmuir isotherm) and experimental chromatograms recorded for 46.25 (main figure) and 9.251 mg (insert) of R-l-indanol. The isotherm was determined from the band profile obtained for 46.25 mg. (Right) Bi-Langmuir isotherms obtained by the inverse method (lines) and by frontal analysis (symbols) for the R- and S-l-indanol enantiomers. Cmax indicates the maximum elution concentration. Reproduced with permission from A. Felinger, D. Zhou, G. Guiochon, /. Chromatogr. A, 35 (2003) 1005 (Figs. 2 and 3).

Obviously, when Ca = 0, the isotherm of the first component reduces to a Langmuir isotherm. This model was used to account for the adsorption of the enantiomers of 1-indanol on cellulose tribenzoate [51]. 

For very dilute solutions, hence at low spreading pressiues, the concentrations of the adsorbates are also low, and the activity coefficients in the adsorbed phase approach unity. For real solutions, a suitable model of the activity coefficients must be used. Several such models have been suggested. The following equation, proposed by Gamba et al. [62] and based on the regular solution theory [63], was applied by Kaczmarski et al. [51] to account for the competitive isotherm of 1-indanol on cellulose tribenzoate ... 

Figure 4.18 Experimental competitive adsorption data (symbols) and best competitive T6th isotherms (solid lines) for the enantiomers of 1-Phenyl-l-Propanol on cellulose tribenzoate. Symbols , R-PP y, S-PP. Reproduced with permission from K. Kacz-marski, A. Cavazzini, P. Szabelski, D. Zhou, X. Liu, G. Guiochon,. Chromatogr. A, 962 (2002) 57 (Fig 1).

Previous work [126] had shown that the FOR model accounted well for the overloaded band profiles of samples of mixtures of various compositions of the enantiomers of indanol on cellulose tribenzoate, in a wide range of sizes. However, this was possible only by letting the effective diffusion coefficients of the two enantiomers float. The best values of these coefficients depended on the sample size. This suggested an important model error, the influence of surface diffusion... 

The equilibrium isotherm data of the two enantiomers of 1-indanol were measured with FA on a microbore column (i.d. 1 mm) packed with Chiralcel OB (cellulose-tribenzoate coated silica from Chiral Technologies) and eluted with a solution of n-hexane and 2-propanol (92.5 7.5) [80]. The amotmt of sample needed... 

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