A comparative study of the determination of the stability constants of inclusion complexes of p-sulfonatocalix[4]arene with amino acids by RP-HPLC and H-1 NMR

Reversed-phase high-performance liquid chromatography (Separon SGX C 18, UV detection at 254 nm and acetonitrile-water-trifluoroacetic acid (70:30:0.5, v/v), and methanol-water-trifluoroacetic acid (3:97:0.5, v/v) as mobile phases) was applied to the study of the host-guest complexation of p-sulfonatocalix[4]arene (SC[4]A) with amino acids as guests in the mobile phase. It was established that the formation of the inclusion complexes results in changes in the retention times of the amino acids. Stability constants of the complexes were determined. The variations in stability constants may be explained in terms of the various interactions (ion-pairing, hydrophobic, aromatic-aromatic and electrostatic interactions) that may occur between a given amino acid and SC[4]A. For the amino acids aspartic acid and proline the association constants were also derived from H-1 NMR experiments.