Raman, Infrared, and Laser-Induced Breakdown Spectroscopy Identification of Particles in Raw Materials.

Abstract

Raw materials need to be of a certain quality with respect to physical and chemical composition. They also need to have no contaminants, including particles, because these could indicate raw material impurities or contaminate the product. Particle identification allows determination of process conditions that caused them and whether the quality of the final product is acceptable. Particles may appear to the eye to be very different things than they actually are. They may be coated with the raw material and may consist of several components; therefore, chemical and elemental analyses are required for accuracy in proper identification and definitive information about their source. Thus, microscope versions of Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS), and infrared (IR) spectroscopy are excellent tools for identifying particles in materials. Those tools are fast and accurate, and can provide chemical and elemental composition as well as images that can aid identification. The micro-analysis capabilities allow for easy analysis of different portions of samples so that multiple components can be identified and sample preparation can be reduced or eliminated. The differences in sensitivities of Raman and IR spectroscopies to different functional groups as well as the elemental analysis provided by LIBS and the image analysis provided by the microscopy makes these complementary techniques and provides the advantage of identifying various chemical components. Proper spectral searching techniques and interpretation of the results are important for interpretation and identification of trace contaminants.