Amorphous Oxide Surfaces as Metal Cation Sequestrating Agents

Modified Amorphous Oxide Surfaces as Metal Cation Sequestrating Agents 

Many modified surfaces do not have coordinating species, as in the case of the well-known modified surfaces, for example, CIS, used in gaseous or liquid chromatography. However, if the organomodifing agent has one or more coordinative sites (and this is frequently the case) the modified surface can be successfully used to promote the withdrawl of metal cations from aqueous and nonaqueous solutions [3]. Solution calorimetric studies [3] have shown that the total amount of adsorbed (chemisorbed = coordinated) cations is a function of two main factors the acid-base interactions between the metal cation (Lewis acid) and the coordinative site on the modified surface (Lewis base) and the metal cation-solvent interactions. 

Organofunctionalized Metal-Modified Surfaces for Chromatographic Applications 

The preparation of organically modified oxide surfaces for chromatographic purposes (some of them very specific) is a very rich and productive field of research. A few examples are presented in the following sections. 

It has been shown that organofunctionalized silica surfaces further modified with in situ synthesized copper complexes can be used to produce new stationary phases for HPLC [4]. The immobilized copper complexes provide new sites in the stationary phase that can interact strongly with basic organic compounds. A test mixture of compounds such as benzene, toluene, naphthalene, anthracene, pyrene, and nitrobenzene shows that the presence of copper ion complexes on the modified surface strongly affects the retention factor (fe) of the stationary phases. 

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