Complexation and chromatographic studies involving water soluble calixarenes and nitrophenols

In this study, an investigation of the utilisation of the sodium salts of 4 -sulphonic calix[4]arene and 4-sulphonic calix[6]arene as mobile phase addi tives in reversed phase HPLC is described. Consistent with earlier work the se mobile phase additives were shown to strongly influence the retention be haviour and separation factor of 2-, 3- and 4-nitrophenols. Proton NMR and UV spectroscopic data is presented to demonstrate that this chromatographic behaviour is due to pH effects and not due to complexation between the nit rophenols and the calixarenes.