Direct Comparison of the Capabilities of Photoacoustic and Diffuse Reflectance Spectroscopies in the Ultraviolet, Visible, and Near-Infrared Regions

A direct comparison of the capabilities of photoacoustic (PA) and diffuse reflectance (DR) spectroscopies in the ultraviolet, visible, and near-infrared spectral regions was made by collecting both types of spectra under nearly Identical conditions. This comparison focused on the following aspects: (1) signal-to-noise ratio and sensitivity; (2) spectral definition and those factors, such as saturation and particle size, which affect spectral definition; and (3) sample preparation considerations for both qualitative and quantitative analysis. In terms of signal-to-noise ratio and spectral definition the two techniques are virtually indistinguishable for weakly absorbing, finely divided powders. DRS is slightly more sensitive but has a lower saturation limit than does PAS and is more severely affected by changes in particle size. For particles larger than 100 μm, DR spectra are distorted and spectral definition is degraded. In terms of sample preparation, especially when only qualitative results are desired, PAS is clearly superior. For quantitative results both techniques require careful control of particle size, packing density, and total absorption. © 1986, American Chemical Society. All rights reserved.

Duke Scholars

Author Richard A. Palmer Chemistry