However, the DBD–Met enantiomers could not be separated on the CHIRACEL OD-R column but were well separated on the CHIRACEL OJ-R column as were the DBD–Ate isomers. The separation of the DBD–Met and DBD–Ate isomers are shown in figure 49 (chromatogram A, DBD–Met and chromatogram B, DBD–Ate).

Courtesy of the Royal society of Chemistry, Ref. [12]

Figure 49 The Separation of Derivatized Metoprolol and Atenolol at High Sensitivity

Each enantiomeric pair represents 50 pmol of the original drug. The separation was carried out on the CHIRACEL OJ-R column (15 cm long, 4.6 mm I.D., packed with particles 5 mm in diameter coated with the cellulose ester. The mobile phase used for the separation of DBD–Met was methanol/acetonitrile : 90/10 v/v, at a flow rate of 0.5 ml/min., the separation ratio was 1.33. The mobile phase used for the separation of DBD–Ate was methanol, also at a flow rate of 0.5 ml/min., the separation ratio being 1.53. The excitation wavelength was 450 nm and the emission wavelength was 560 nm. The fluorescent derivatives were found to be stable at 4°C for over 1 week. The detection limits at a signal-to-noise ratio of 3 were 50 fmol for both (S)- and (R)-Propanolol, 12 and 17 fmol for (S)- and (R)-Metroprolol respectively and 15 and 20 fm for (S)- and (R)-Atenolol respectively.

Beta Blockers Using Cyclodextrin

The cyclodextrin based stationary phases are some of the more popular and effective chiral stationary phases presently available. One of their distinct advantages lies in their unrestricted and successful use with all types of solvent. In particular, they can be used very effectively in the reversed phase mode (a method of development that is not possible with some other chiral stationary phases) as well as being very effective in a normal phase conditions. They can also be used in the so-called polar organic mode, where the polar constituents of the mobile phase can be anhydrous diethylamine or glacial acetic acid, but in the complete absence of water. The cyclodextrins and their derivatives are widely used for all types of chiral separations, they have a good sample capacity, and can often be used for preparative separations. Cyclodextrin-based phases are readily available, usually covalently bonded to spherical silica gel particles 5 mm in diameter. There are numerous examples of the use of cyclodextrins in chiral separations and the following are some applications that illustrate their general use.