Principles and Practice of Chromatography - Chromatography Applications > Liquid Chromatography Applications > Analysis of β-blockers > Page 91

 

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.

 

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.

Cyclodextrin based chiral stationary phases have also been used to separate b blocking agents in conjunction with an optically active fluorescent Edman-type reagent to enhance detection. Toyo'oka and Liu [15] used the optically active Edman type fluorescent reagents, 4-(3-isothiocyanatepyrrolidin-1-yl)-7-nitro-2,1,3-benzoxadiaz-ole [(r)-() and (S)-(+)-NBD-PyNCS] and 4-(3-(3-isothiocyanatepyrrol-idin-1-yl)-7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxydiazole [(R)-()-and (S)-(+)-DBD-PyNCS] to produce diastereomers that could be separated on a simple reversed phase column and, at the same time, provide enhanced sensitivity.