The Gemperline research group is currently working on a research project to characterize chemical batch reactions in slurry mixtures with light scattering properties. One of our primary goals is to determine light absorption and light scattering properties of these mixtures using near-infrared (NIR) reflectance measurements in order to characterize the amount of reactants and products in the solution phase and in the solid phase. Resolving light scattering properties from light absorbing properties in slurries is challenging because they strongly interact in a nonlinear way. Temporally resolved and spatially resolved diffuse reflectance measurements are two well-established methods of determining the coefficients related to these properties in light scattering samples. This literature review will present recently developed calibration methods for estimating light absorption and light scattering coefficients from time resolved and spatially resolved reflectance measurements. Temporally resolved diffuse reflectance has been shown to accurately determine the optical properties and particle sizes of granular samples of dyed silica gel [1], and spatially resolved measurements have been demonstrated to accurately measure the properties of tissue-simulating phantoms [2]. A comparison of these two methods has shown their use in taking measurements of known tissue phantoms, in vitro, and in vivo samples [3]. This comparison will be used to discuss the applications and the limitations of these techniques.

[1] Pandozzi, F. (2007). Power Law Analysis Estimates of Analyte Concentration and Particle Size in Highly Scattering Granular Samples from Photon Time-of-Flight Measurements. Analytical Chemistry, 6792-6798.
[2] Dam, J. (2001). Fiber-optic probe for noninvasive real-time determination of tissue optical properties at multiple wavelengths. Applied Optics, 1155-1164.
[3] Swartling, J. (2003). Comparison of spatially and temporally resolved diffuse-reflectance measurement systems for determination of biomedical optical properties. Applied Optics, 4612-4620.