MATRIX INFLUENCE ON STABILITY-CONSTANTS OF 15-CROWN-5-ALKALI METAL-COMPLEXES MEASURED BY LIQUID SECONDARY-ION MASS-SPECTROMETRY

The liquid secondary ion mass spectra of 15-crown-5 in the presence of equimolecular mixtures of three alkali metal salts show large changes in the relative abundances of the 15-crown-5-cation complexes formed, depending on the relative concentrations of ligand and salts. These v ariations are due either to various desorption rates of the cationized species or to different affinities of 15-crown-5 toward the alkali me tal cations. An original method allowing discrimination between desorp tion and complexation effects on the relative abundance of ligand-meta l complex ions is described and can be applied for the calculation of their stability constants. The spectral data obtained using two differ ent matrices demonstrate that the matrix polarity has a very important effect on the two parameters considered, i.e. the stability constants of the 15-crown-5-cation complexes and their desorption rates.