Conservative Quantification of Amino Functionalities Chemically Bonded on Porous Solid

Amino-functionalized solid materials, involving basic groups, such as -NH2, -NHR, -NR2, are widely employed in a variety of applications, especially in the field of CO2 capture and storage technologies, focused on environmental and industrial purposes, as well as in that of the separtions technology, which finds very large enforcement within both academic and pharmaceutical context. In particular, in the role of stationary phases for chromatographic techniques, amino groups are commonly linked to solid matrices of silica through alkyl chains, which, for example, can be successfully employed in HILIC applications and, in general, in the effective resolution of resctricted but important classes of compounds (e.g. mixtures of mon- or oligo-saccharides). In this communication we are going to present an original, really effective and operatively simple procedure, developed with the aim to quantify the density of amino groups chemically bonded to the surface of porous solids and to ensure a full recovery of the material (i.e. "conservative" mehod). This approach is based on the salification of the amino-functionalities through a species (HAUV) of suitable acidity and UV absorptivity. The quantification is then performed either by retro-titrating, via UV spectrophotometry, the HAUV displaced from the salt by addition of a stronger acid, or directly, by analyzing the characteristic vibrational bands of the salified material by IR spectrometry in the presence or in the absence of suitable external standards.