Relationship between Raman Scattering Intensity in the Aromatic Region and the Thermally Induced Increase in the Uv Absorption of Chemically Bonded Stationary Phases

In the initial papers reporting the thermal instability of chemically bonded stationary phases on irradiation with a high-power neodymium laser, Raman scattering intensity in the region 2285 to 1130 cm was found to depend on the density of coverage of the silica matrix with alkyl ligands. Further research focused on the dependence of the growth of UV absorption in this region, on heating of the stationary phase, on the density of coverage of the silica matrix with alkyl ligands capable of aromatization. For thermal modification of the RP-2 stationary phase impregnated with paraffin oil a quantitative dependence was found between the growth of absorption in this UV region and the paraffin oil-content of the chromatographic bed. In this study the relationship between the thermally induced increase in UV absorption of RP-8 and RP-18-type stationary phases and Raman-scattering intensity in the aromatic region when the stationary phases are irradiated with a high-power neodymium laser is discussed. The results obtained confirm the assumption of a linear relationship between the growth of UV absorption in this region by the stationary phase as a result of its thermal modification and the density of coverage of the silica matrix with alkyl (octyl or octadecyl) ligands capable of aromatization.