Comparing the Enantioselectivity of Cyclodextrin-Based GC Chiral Stationary Phases

By: Len Sidisky, Kathy Stenerson, Greg Baney, Reporter US Volume 27.4

Supelco currently offers a wide selection of cyclodextrin-based chiral stationary phases. The most versatile and popular commercial stationary phases are prepared using alpha-, beta- or gamma-cyclodextrins that have been functionalized with various derivative groups at the 2, 3, and 6 positions on the sugar molecules. Functional groups used to derivatize the cyclodextrins include trifluoroacetyl, permethyl, dimethyl, diacetyl and others. Each of the functional groups imparts a unique enantioselectivity on the resulting chiral stationary phase.

We recently compared the selectivity of four popular chiral GC stationary phases using a series of test probes. The phases we studied include the Supelco β-DEX™ 110, β-DEX 120 (both permethylated beta-cyclodextrins imbibed in an intermediate polarity stationary phase), Astec CHIRALDEX® B-DA (a dipentylated beta cyclodextrin) and Astec CHIRALDEX G-TA (a gamma-cyclodextrin trifluoroacetylated at the 3-hydroxy position and pentylated at the 2- and 6-hydroxy positions).The Supelco β-DEX 110 and 120 and the Astec CHIRALDEX® B-DA phases are thought to interact with chiral compounds primarily using an inclusion mechanism to affect the separation of the chiral moieties. The Astec CHIRALDEX G-TA interacts primarily using a surface interaction with the chiral compounds.

The temperature-programmed analysis of seven chiral probes shows the Supelco β-DEX 110 and 120 phases provide similar polarity and chiral selectivity, though there are differences in their selectivity (Figure 1). These phases provide chiral resolution primarily via inclusion complexation. The Astec CHIRALDEX B-DA column did not provide the chiral selectivity for the compounds evaluated compared to the permethylated and Astec CHIRALDEX G-TA phase. This phase also uses inclusion complexation as its primary separation mechanism. The Astec CHIRALDEX G-TA column had the best chiral selectivity for the compounds used in this study. The G-TA uses surface interactions as its primary mechanism to resolve chiral compounds, and has broad applicability for a variety of chiral compounds.

 

Figure 1. Selectivity of 4 Chiral GC Stationary Phases (Chiral columns used: 24301 24304 72023AST and 73033AST)

The Supelco DEX and Astec CHIRALDEX lines comprise many more phase chemistries than described here. The columns are also available in convenient and economical kits containing the most popular phase chemistries. A partial listing is shown. To view the complete list, please visit sigma-aldrich.com/chiral-chromatography.

back to top 

Materials

     

 

Trademark Attributions:

  • CHIRALDEX is a registered trademark of Sigma-Aldrich Co. LLC
  • DEX is a trademark of Sigma-Aldrich Co. LLC

 

Related Links