There are several methods available to the researcher interested in investigating the differences in composition at different depths in a sample. These techniques include attenuated total reflectance (ATR), diffuse reflectance (DRIFTS) and infrared microscopy. Another method available for depth analysis of samples is photoacoustic spectrometry (PAS). Photoacoustic spectrometry requires little sample preparation and samples can be measured in bulk form without the need to modify (grind, slice, etch), eliminating the possibility of inducing changes in the sample. Photoacoustic spectrometry can be used to characterize coatings, weathered surfaces, surface oxidation, segregation in polymer blends, surface morphology or multilayer laminates.