Scattering Orthogonalization of Near-Infrared Spectra for Analysis of Pharmaceutical Tablets

Abstract

The paper explores scattering orthogonalization as a preprocessing technique to reduce physical interference and maintain chemical information in near-infrared (NIR) spectra of pharmaceutical tablets. Samples used in this study were tablets compressed at five compression forces; they were composed of theophylline, lactose, and microcrystalline cellulose (PH200). The NIR spectra were orthogonalized against the reduced scattering coefficients (representative of physical interference of scattering), and concentrations of all constituents were predicted. The robustness of predictions was compared to the widely employed standard normal variate (SNV) for the specificity of removing interference representative of physical parameter (such as tablet density). Group-wise cross-validation (groups were based upon similar chemical composition) and prediction demonstrated the enhanced robustness on prediction of chemical information via scattering orthogonalization in comparison to SNV. When compared to the SNV, scattering orthogonalization demonstrated an improved capacity to reduce physical interference while maintaining spectral variance attributable to chemical information. The improved capacity is expected to be useful for spectroscopy-based multivariate model calibration and continuous model update.

Pharmaceutical Applications of Separation of Absorption and Scattering in Near-Infrared Spectroscopy (NIRS)

“…34 Detection could be accomplished using one single fiber moving radially and measuring reflectance one radial distance at a time, or using a linear fiber array picking up signal simultaneously from different radial distances. With the development of imaging technology, charge‐coupled device (CCD) cameras have emerged as a means of detecting radially diffused reflectance 5, 50–52. The advantage of using CCD cameras to capture the entire radial distribution of diffusively reflected signals is to enhance the signal‐to‐noise ratio of the reflectance measurements via spatial image processing (i.e., signal binning) of equivalent radial distances 50…”

“…The two main purposes of the separation are to improve the understanding of individual roles played by absorption and scattering in NIRS, and to utilize the separated absorption and scattering spectra for qualitative and quantitative applications. To date, five techniques to separate NIR absorption and scattering of pharmaceutical related materials have been reported: spatially resolved spectroscopy,5–8 frequency‐resolved spectroscopy,9–21 time‐resolved spectroscopy,22–27 the integrating sphere based reflectance and transmittance measurements,28–31 and measurements of remission, absorption and transmission fractions through layers of material of different thicknesses 32, 33. A review of how these techniques are applied specifically to pharmaceutical application has yet to be reported.…”

Optical porosimetry and investigations of the porosity experienced by light interacting with porous media

“…Understanding of the interaction of light and turbid porous materials is of fundamental importance in many areas-from fundamental studies of photon localization in porous semiconductor materials [1,2] to analysis of chemistry, pore structure and optics of powders and pharmaceutical materials [3][4][5], porous ceramics [6][7][8], and porous silicon [9,10]. Throughout the years, massive efforts have been put into developing models for the macroscopic aspects of photon migration in turbid materials.…”

Analysis of pharmaceutical products and herbal medicines using ambient mass spectrometry

“…Pharmaceutical analysis, as an important approach to understand the active pharmaceutical ingredients and impurities, to ensure the efficacy and safety, as well as to develop methodologies for quality assessment and control of pharmaceutical products and herbal medicines, has been a hot research topic in recent years. Huge efforts have been spent in this field, with different techniques including optical spectroscopy [5][6][7], chromatography [7][8][9][10][11][12][13][14], and mass spectrometry (MS) [12][13][14][15][16][17][18][19][20], etc., have been developed in the past several decades. The chromatography and chromatography coupled with MS techniques have been proven to be the powerful tools due to their properties of excellent sensitivity, desirable specificity, and reasonable qualitative and quantitative capability.…”