CHIRALDEX TA

Astec CHIRALDEX A-TA, B-TA, and G-TA capillary GC columns incorporate a phase consisting of a 2,6-di-O-pentyl-3-trifluoroacetyl derivative of either α-, β-, or γ-cyclodextrin. These phases exhibit high selectivity for oxygen containing analytes in the form of alcohols, ketones, acids, aldehydes, and lactones. They are also highly selective for halogenated compounds.

Features

• Separate the widest variety of enantiomers
• Separate the greatest number of enantiomers
• G-TA more selective than B-TA
• Unique retention behavior
• Extraordinary versatility and chiral selectivity
• Useful for homologous series of:
  • Amino acids (primary, secondary, aliphatic, and aromatic)
  • Amines (primary, secondary, cyclic, aromatic, and halogenated)
  • Amino alcohols
  • Alkanes, hydrogenated alkanes
  • Alcohols (aliphatic and aromatic)
  • Acids (halogenated and hydroxy)
  • Esters (aliphatic, aromatic, hydroxy, and di-ester)
  • Diols
  • Lactones
  • Ketones
  • Phthalides
  • Sulphoxides

Mechanism Observations

• Strong dipole-dipole interactions
• Longer alkyl chain; greater retention; increase in enantioselectivity up to C4/C5
• Halogens known to favor cavity interaction

Dipole-dipole interactions are commonly identified in the mechanism of separation for the TA phases. In a homologous series of alkane enantiomers, identical alpha values are observed regardless of chain length or branching, indicating only 1 or 2 carbons may be contributing to chiral recognition. Alpha values are greatly affected by size and polarity of the head group. Functional groups like epoxides, amino alcohols, and alcohols can dictate the cyclodextrin selection. Aldehydes, carboxylic acids and epoxides separate better on the G-TA while alcohols, alcohol amines, and other linear molecules separate better on the B-TA.

Size Selectivity

The G-TA has proven to exhibit a wider chiral selectivity and usefulness than the B-TA. The influence of the inclusion mechanism for chiral recognition is very much reduced and capacities are generally higher indicating more surface interaction. Of all the compounds tested, the split between G-TA and B-TA is approximately 55/35 with only 10% of the separations accomplished on the A-TA.

Important Notice About Astec CHIRALDEX TA Columns

The TFA derivative of the cyclodextrins used in Astec CHIRALDEX TA phases will hydrolyze in the presence of moisture at room temperature or above. Sources of moisture include injected samples, the carrier gas, or air during unsealed storage. To ensure long column life, be sure all samples are free of moisture before injecting, that the sample solvent (i.e., ethyl ether, methylene chloride, etc.) is anhydrous, and that the carrier gas has an efficient and functional moisture trap. To properly seal an Astec CHIRALDEX TA column for storage, the column must be heated to 160 °C under normal chromatographic conditions for one hour and flame sealed. If sealed under vacuum, it will then store indefinitely.

Specific Classes of Compounds Separated

Use this table as a reference to help determine the proper column based on the analyte(s) of interest.