UNDERSTANDING MOLECULAR ASSOCIATION AND ISOMERS RECOGNITION IN ISOMER-CYCLODEXTRIN MULTIPLE COMPLEX-FORMATION BY IMPROVED LIQUID-CHROMATOGRAPHIC STUDIES

Equations are derived that allow the determination of guest-cyclodextr in primary (K-11), secondary (K-12), and higher order (K-1n) binding c onstants as well as the degree of complexation (n) over bar (the perce nt of complexed guest), by monitoring the observed capacity factor k'( obs) for guests that can be structural, geometric, or optical isomers, The retention behavior (elution order) in a mixture of isomers is dep endent on the cyclodextrin concentration in the mobile phase as well a s on the stoichiometry and the binding constant of the guest-cyclodext rin (G-CD) complex, The simplification of higher order complexes (G-CD n) to that with 1:1 stoichiometry can lead to erroneous results; there fore, it is important for the stoichiometry to be determined accuratel y, prior to any binding constant calculations, following the continuou s variation method, The proposed models are solved iteratively using n onlinear least-squares analysis and following specific algorithms.