OVM CSP

The binding interactions between the solute and protein usually involves stereospedfic and nonstereospecific mechanisms. These mechanisms make the type V CSPs sensitive to the composition of the mobile phase, temperature, flow rate, and pH. These parameters can be adjusted to improve the chromatography and stereoselectivity of specific solutes on the AGP CSP (88,89), OVM CSP (90,91), BSA CSP (92,93), and HSA CSP (94). 

As with the other protein-based CSPs, initial studies indicate a relationship between the structure of the protein and chromatographic properties of the OVM CSP (101). When the sialic acid residues, were enzymatically removed from the protein, the capadty factors (k ) of the enantiomers of an addic solute (ketoprofen) were reduced, whereas the k s of the enantiomers of a basic solute (chlorpheniramine) were un-... 

Since ovomucoid is a glycoprotein the solutes that can be stereo-chemically resolved on the OVM CSP are similar to the basic, neutral, and acidic compounds separated on the AGP CSE The major differences between the two CSPs appears to be quantitative i.e the magnitude of the chiral separation), rather than qualitative. The two CSPs have been recently compared and a representative series of successfully resolved solutes is contained in this article (102). 

The basic mobile phase used with the OVM CSP is composed of phosphate buffer and one or more modifiers. The type and concentration of the mobile-phase modifier as weU as the pH are extremely important and both k and a can be altered by changing the mobile phase (102). 

The effects of alcoholic modifiers and pH on the chromatographic properties of the OVM CSP have been investigated using acidic, basic, and neutral solutes (103). A series of primary, secondary, and tertiary alcohols and pH s ranging from 3.5-6.0 were used in this study. The results indicate that both the shape and hydrophobicity of the alcoholic modifier affect retention (k ) and enantioselectivity (a). In general, an increase in the hydrophobicity of the modifier results in a decrease in k s and a s. However, this is not the case when (-butanol is the modifier, suggesting that the size of the alkyl moiety attached to the carbinol carbon also contributes to the chromatographic results. The pH studies indicated that... 

Because the OVM CSP is a relatively new CSR only one pharmacokinetic application has been reported. Because of the utility of this phase, it is evident that such a situation will quickly change. 

The purpose of this study is only intended to illustrate and evaluate the decision tree approach for CSP prediction using as attributes the 166 molecular keys publicly available in ISIS. This assay was carried out a CHIRBASE file of 3000 molecular structures corresponding to a list of samples resolved with an a value superior to 1.8. For each solute, we have picked in CHIRBASE the traded CSP providing the highest enantioselectivity. This procedure leads to a total selection of 18 CSPs commercially available under the following names Chiralpak AD [28], Chiral-AGP [40], Chiralpak AS [28], Resolvosil BSA-7 [41], Chiral-CBH [40], CTA-I (microcrystalline cellulose triacetate) [42], Chirobiotic T [43], Crownpak CR(-i-) [28], Cyclobond I [43], DNB-Leucine covalent [29], DNB-Phenylglycine covalent [29], Chiralcel OB [28], Chiralcel OD [28], Chiralcel OJ [28], Chiralpak OT(-i-) [28], Ultron-ES-OVM [44], Whelk-0 1 [29], (/ ,/ )-(3-Gem 1 [29]. 

The usefulness of protein-type CSPs has already been shown in particular Chiral-AOP and Ultron ES-OVM (see Table 2) have a very broad range of enantioselectivity. It is not, however, possible to systematically predict the resolution on such CSPs, but the overall retention, selectivity and efficiency can be modified to a certain extent by altering several key variables ... 

A number of proteins are commercially available as CSPs including a-acid glycoproteins (AGP, the major plasma binding protein for basic drugs), human serum albumin (HSA, the major plasma binding protein for weakly acidic drugs), bovine serum albumin (BSA), ovomucoid (OVM), and cellobiohydro-lase (CBH) [12]. The proteins are bonded to silica and utilized in reversed-phase mode with an aqueous buffer/organic modifier eluent. Mobile-phase... 

Fig. 9.38. Loadability of different CSPs under bateh-ehromatography arnditions. (a) Triigcr base on Chi-ralpak AD methanol vs. aeetonitrilc (

The ability of proteins to stereoselectively bind small molecules has been used to develop a series of commerdally available protein-based CSPs (the type V HPLC CSPs), including phases that contain immobilized AGP (84), HSA (85), BSA (86), and ovomucoid (OVM) (87) (see Table 5). All these CSPs are useful in the HPLC resolution of enantiomeric compounds and appear to have an extremely wide range of applications, and the AGP CSP seems to have the broadest utility of any of the current CSPs (9-11). However, although the type V CSPs display high enantioselectivities, they also have low capadties due to the relatively small amounts of the chiral selector that can be immobilized per g silica. Thus, these CSPs are useful... 

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