Thermoanalytical study of chemically modified stationary phases used in thin-layer chromatography

The hydroxylated surface of silica gel R has been chemically modified with polar (amino, mercapto) and nonpolar (n-octyl, n-octadecyl) trifunctional o rganosilicon compounds, The materials obtained can he used as stationary ph ases in TLC for the separation and identification of different classes of c ompounds, In this paper, TG, DTG, and DTA thermoanalytical methods have bee n used to study these chemically modified stationary phases. A comparative study of TG, DTG, and DTA thermoanalytical curves has been performed. The t emperature ranges of the thermal effects which occur and the corresponding mass loss values mere established. This study of the thermoanalytical curve s shows that water removal and partial decomposition of the organic compone nt give rise to endothermic and exothermie effects. The mass loss depends o n the type of silica gel, unmodified or chemically modified, and on the nat ure and length of the chain bonded to silica gel surface. Thermal analysis gives quantitative information about the mater and organic content of the stationary phases studied. TG, DTG, and DTA can be regarded as useful techniques for supplementary study of the chemically modified st ationary phases used in thin-layer chromatography.