INORGANIC ANALYSIS IN ORGANIC SOLVENTS .3. ADSORPTION CHARACTERISTICS OF METAL CHELATE COMPOUNDS ON ALUMINAS AND SILICA GELS

The general adsorption characteristics of 8-quinolinol, aetioporphyrin, β-diketone and 8-quinolinethiol chelates of metals are described. These, with adsorption isotherm studies, indicate that the mechanism is of a chemisorption type with, in the case of oxo-chelating agents, high heats of adsorption. It appears that hydrogen-bonding to Brønsted sites on the adsorbents is an essential feature of the process and that multilayers of adsorbate are readily formed. This observation is supported by rate studies which show that the adsorption is a twostage process with a break at a point corresponding to monolayer coverage. Both stages are diffusion controlled with relatively low probability. Infrared and X-ray diffraction studies, although of limited value, support these conclusions. The requirements of more generally applicable chelating agents and adsorbents for analytical purposes are discussed and predicted. © 1969.