Chiral Selector with an Achiral Surfactant

This mode can give added selectivity to resolution of both neutral and charged chiral molecules, as the solutes are distributed between chiral selector such as a CD, the aqueous phase and the micelle (Figure 6). As a result, the chiral analytes will move in and out of the micelle/CD, with the CD moving with the EOF and the micelle (depending on polarity) moving according to charge. Racemic amino acids, ^-blocker drugs, Trogers base and the drug terbutaline have all been resolved with this procedure. In the case of terbutaline either 5 mmol L"1 di-O-methyl-^-cyclodextrin or 15 mmol L"1 ^-cyclodextrin was successfully used with 15 mmol L"1 SDS. Other approaches have been to carry out competetive separations with CD-MEKC, where an additive, such as d-camphor-10-sulfonate, is introduced into the buffer and competes for inclusion with the chiral analytes. With this procedure an improved resolution of Trogers base was obtained. Overall, this form of

Time (min)

Figure 5 The use of bile salts to resolve the enantiomers of diltiazem and related substances by chiral micellar electrokinetic chromatography (MEKC). The electrolyte was 20 mmol L"1 disodium hydrogen phosphate-sodium tetraborate (pH 7.0) containing 50 mmol L"1 sodium taurodeoxycholate. The capillary was 65 cm (50 cm to detector) x 50 ^m i.d. Applied voltage was 20 kV, detection wavelength was 210 nm and temperature was 25°C.

Time (min)

Figure 5 The use of bile salts to resolve the enantiomers of diltiazem and related substances by chiral micellar electrokinetic chromatography (MEKC). The electrolyte was 20 mmol L"1 disodium hydrogen phosphate-sodium tetraborate (pH 7.0) containing 50 mmol L"1 sodium taurodeoxycholate. The capillary was 65 cm (50 cm to detector) x 50 ^m i.d. Applied voltage was 20 kV, detection wavelength was 210 nm and temperature was 25°C.

separation of chiral analytes has become quite popular, particularly as there are many derivatized CDs to choose from, and many examples have been published. Of the native CDs, y-CD has shown the greatest success, which is the opposite of the case with the conventional addition of CDs to the buffer phase. In this case the larger inner diameter of the cavity of the y-CD allows not only the chiral molecules to be included but also the surfactant.

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