The factors affecting the reflectance spectra of some dyes adsorbed on alumina

Various factors affecting the diffuse reflectance spectra of eosin B, rhodamine B, fuchsin, and o-nitrophenol adsorbed on Chromatographic alumina under various conditions were studied to explore the potential analytical application of reflectance spectroscopy to dyestuffs separated by thin-layer chromatography. Regeneration temperature, pH and grade of adsorbent, and humidity were found to influence the spectra but the technique may be utilized for the photometric analysis of food dyes adsorbed on alumina ; straight lines passing through the origin were obtained when the Kubelka-Munk function was plotted against a suitable concentration range of dye. For reproducible results, it is essential to employ the same grade of adsorbent and to prepare samples under uniform conditions of humidity.