CONICET | Buscador de Institutos y Recursos Humanos

A different chromatographic behaviour for many drugs containing amino and -OH groups in adjacent carbons (b-blockers and alkaloids) when using mobile phases of the same pH and organic modifier composition, but prepared from different buffers, has been reported in a recent work [1]. It has been observed that retention times of these analytes in presence of tris buffer are increased in relation to dihydrogenphosphate buffer, so this extra retention in presence of tris must be based on retention mechanisms besides the own hydrophobicity of the analyte. In the present work the chromatographic behaviour of several drugs (mainly b-blockers) is systematically studied in mobile phases containing tris or dihydrogenphosphate as buffering species, at different concentration and pH. The results are compared with the ones corresponding to relatively simpler aminophenols, which present the amino group in ortho, metha and para positions in relation to the -OH group and different substituents. In these cases no significant differences are observed in the chromatographic behaviour of the analytes when tris, dihydrogenphosphate or piperazine buffers were used, independently of the molecular structure and bonding of the studied aminophenols. Finally, with the aim of solving this controversy, a detailed study of the existence or absence of buffer-analyte interactions is carried out, outside of the chromatographic system, by means of isothermal titration calorimetry