Anal. Chem. 1986, 58,3167-3172
3167
Quantitative Variable-Temperature Diffuse Reflectance Infrared Fourier Transform Spectrometric Studies of Modified Silica Gel Samples R. S. Shreedhara Murthy, J. P. Blitz, and D. E. Leyden* Condensed Matter Sciences Laboratory, Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
The thermal expanslon of the sample post during varlabletemperature (VT) dlffuse reflectance Infrared Fourler transform (DRIFT) spectrometric studles displaced the plane of the sample, whlch resutted In undesirable changes In the spectral Intensity of all the bands. Hence, the dlffuse reflectance accessory (Harrlck SclentlHc Corp.) was modlfled to accommodate a onedlmerrsional vertlcal translatlon stage for height adjustment (with a resolutlon of f0.014 mm) so that the plane of the sample could be precisely located at the opthnutn posltlon. Studles with modtfled sllka gel samples showed that lowerlng the sample at 200 OC by 0.14 mm successfully compensated for the Increase In sample helght (calculated to be 0.11 mm for a temperature Increase from 25 to 200 "C) due to thermal expansion. Relativedo the band area at the optlmum helght and at room temperature, the SI-0 stretch band at 806 cm-' was the least affected by slllca gel concentration and temperature. Hence, this band was chosen as the reference for obtaining band area ratlos. A 1-2% (w/w) disperslon of modlfled slllca gel (
