Power Law Analysis Estimates of Analyte Concentration and Particle Size in Highly Scattering Granular Samples from Photon Time-of-Flight Measurements

Abstract

Optical measurements of particle size and composition in granular samples are difficult to make due to complex light scattering from particles. These multiple scattering events bias absorption estimates and complicate the calculation of scattering and absorption coefficients used to estimate sample properties. Time series data, such as chromatograms and photon time-of-flight (TOF) profiles, contain self-repeating (fractal) characteristics. Power law analysis of photon TOF profiles allows the determination of absorption coefficients and particle sizes in a single experiment. A correlation dimension algorithm was used on photon TOF data from scattering samples. MLR models were then obtained from correlation dimension plots for the estimation of sample properties. Estimates of particle sizes and absorption coefficients were shown to agree well with theoretical values when compared using independent validation sets. Results show close to a 3-fold and up to a 5-fold decrease in the errors of estimation of dye concentration and particle size, respectively, as compared to steady-state measurements. The power law approach provides a useful means of determining sample properties in highly scattering media.

Near-infrared photon time-of-flight spectroscopy of turbid materials up to 1400 nm

“…Prominent examples of these two related techniques include in vivo blood monitoring, 5,14,15 breast cancer diagnostics via detection of intrinsic tumor biomarkers, 7 studies of brain hemodynamics and cerebral oxygenation, 16,17 and diffuse optical tomography. 18 Emerging applications include calibration-free and quantitative analysis of pharmaceutical solids, 19 scatter correction of NIRS of pharmaceutical solids, 20 analysis, 21 as well as optical porosimetry ͑PTOFS in combination with gas sensing͒. 22 Until now, PTOFS has been limited to the spectral range below 1100 nm ͑i.e., above ϳ9100 cm −1 ͒.…”

Optical characteristics of wood investigated by time-of-flight near infrared spectroscopy

“…Burns (1997, 1999a,b) performed quantitative measurements in scattering media on the basis of TOF analysis and described the analytical possibilities of the technique. Furthermore, it was also reported that the time-resolved profile was very efficient for estimating the absorption and scattering coefficient (Gributs and Burns 2003a,b;Pandozzi and Burns 2007).…”

Application of Time-of-Flight Near-Infrared Spectroscopy to Fruits: Analysis of Absorption and Scattering Conditions of Near-Infrared Radiation Using Cross-Correlation of the Time-Resolved Profile

“…[6][7][8] Burns et al furthermore reported that experimental analysis of the time-resolved profile was very efficient for estimating the absorption and scattering coefficient. [9][10][11] Many applications utilizing time-resolved reflectance and transmittance have been widely investigated for human head, 12,13 plastic materials, 14 and agricultural or forest products. 15,16 The behavior of transmitted light from the sample is directly affected by the physical and chemical properties of the tissues, making it very important to examine the optical characteristics of them and the output origin of the transmitted light in detail from a new spectroscopic viewpoint.…”