Infrared (IR) spectroscopy can reveal the nature of the adsorbed species in the solid—liquid interfacial region and hence the underlying adsorption mechanisms. Efficiency of physico-chemical separation processes such as flotation and selective flocculation is strongly influenced by the nature of the adsorbed species. The role of IR spectroscopy in understanding the nature of the adsorbed species at the apatite/dolomite-surfactant/polymer interface is discussed. Also, the application of Fourier transform IR spectroscopy in analyzing trace amounts of impurities, and its potential for quantitative analysis of powders is outlined.