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 p hases) was applied to the study of the host-guest complexation of p-sulfona tocalix[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 c hanges in the retention times of the amino acids. Stability constants of th e complexes were determined. The variations in stability constants may be e xplained in terms of the various interactions (ion-pairing, hydrophobic, ar omatic-aromatic and electrostatic interactions) that may occur between a gi ven amino acid and SC[4]A. For the amino acids aspartic acid and proline th e association constants were also derived from H-1 NMR experiments.