Chiral Stationary Phases CSPs Amylose

Simultaneous direct determination of the enantiomers of verapamil and norverapamil in plasma using a derivatized amylose HPLC chiral stationary phase" (53). An AD CSP was used to determine the plasma concentrations of the enantiomers of verapamil and its major metabolite norverapamil. After a liquid-liquid extraction, the analytes were resolved on the amylose column using a mobile phase composed of heptane 2-propanol ethanol, (85 7.5 7.5, v/v/v) modified with 1.0% tri-ethylamine, a flow rate of 1.0 mL/min, and a column temperature of 30 C. The assay was validated for use in human pharmacoldnetic studies. A representative chromatogram is presented in Fig. 5. 

Chiral stationary phases can exist in different forms [10] (see Fig. 8). Some selectors can be used as particulate phase materials, such as polymeric cellulose triacetate. Polymeric cellulose and amylose derivatives are often coated onto silica carrier particles so that only 20% of the CSP consists of the chiral selector. This combination of stationary phase and chiral polymer combines good chromatographic properties (due to the homogeneous particle size distribution) with a high density of chiral adsorption sites in the polysaccharide derivatives. Another approach is selected for the so-called brush-type CSPs. In these, the chiral selector is covalently bound to the surface of the silica particles. These phases show high chemical inertness and allow the use of a multitude of different mobile phases. 

These polysaccharide-based stationary phases appear to be the most useful in organic, bio-organic and pharmaceutical analysis. Of the above-mentioned derivatives three of them, namely cellulose tris-(3,5-dimethylphenylcarbamate), amylose tris-(3,5-dimethylphenylcarbamate) and cellulose tris-(4-methylbenzoate), have very complementary properties and numerous publications have demonstrated that they have been able to achieve the chiral resolution of more than 80% of the drugs currently available on the market. " These CSPs are known under the commercial names, Chiralcel OD-H , Chiralpak AD and Chiralcel OJ , respectively (Figure 4). Their very broad enantiorecognition range is also the... 

More immobilized cellulose and amylose phases are currently tmder development at Daicel. Daicel is promoting the concept of a CSP library of more than 100 stationary phases that are not currently commercially available, which can be screened for enantiomer separations. Astec has recently presented an improved linking of antibiotic phases (Chirobiotic). As yet, no chiral monolithic stationary phases are commercially available, although one can assume that various companies are currently endeavoring to change the surface of monolithic material with chiral modifiers. 

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