On/off chemical determination of reactive amino groups immobilized on silica surfaces

Abstract

Reaction of silica frameworks with aminosilanes to generate reactive amino groups on the surface of solid supports is a widely used step in the chemical modification of such surfaces. These reactive amino groups can aid in the chemical attachment ofproteins (enzymes and/or antibodies)_or chelating agents. Analytical accounting of the reactive groups generated is of interest in method optimization and in reactor design when these materials are used. A nondestructive method for the determination of reactive amino groups after attachment to silica surfaces is presented; it can be used for in-situ determinations in reactors. The method involves on/off chemistry based on the attachment of a chromophoric probe ( p-dimethylaminoinnamaldehyde), its subsequent detachment under different experimental conditions, and spectrophotometric measurement of the released probe at 390 nm. Aspects of covalent attachment of amino groups to silica surfaces are also discussed.