Empirical development of a binary adsorption isotherm based on the single-component isotherms in the framework of a two-site model.
The adsorption behavior of mixtures of the enantiomers of 2,2,2-(trifluoro)-1-(9-anthryl)-ethanol (TFAE) on a quinidine carbamate bonded stationary phase was studied as an example of competitive binary adsorption on a Pirkle-type chiral adsorbent. A model of the adsorption isotherms is proposed and discussed. Binary adsorption isotherms derived by combination of the single-component isotherms of the two enantiomers in the framework of the classical bi-Langmuir model allow the correct prediction of the retention times of the elution bands of the components of binary mixtures but fail properly to predict the separation of the two enantiomers. Use of a quadratic model was needed to improve the agreement between calculated and experimental chromatograms of binary mixtures. The existence of a third type of adsorption sites besides the high-energy enantioselective and the low-energy nonselective sites was assumed. These sites have a low interaction energy, exhibit some affinity toward (S)-TFAE, but none toward (R)-TFAE.
Asnin
Leonid
L
Institute of Technical Chemistry, Ural Division of the Russian Academy of Sciences, Perm 614990, Russia.
Kaczmarski
Krzysztof
K
Guiochon
Georges
G
D000327:Adsorption; D002219:Carbamates / Q000032:analysis / Q000737:chemistry; D002845:Chromatography / Q000379:methods*; D008962:Models, Theoretical; D015394:Molecular Structure; D011804:Quinolines / Q000032:analysis / Q000737:chemistry; D013237:Stereoisomerism; D013816:Thermodynamics
D002219:Carbamates; D011804:Quinolines; C508171:quinidine carbamate