Time-Resolved NIR Spectroscopy for Quantitative Analysis of Intact Pharmaceutical Tablets

Abstract

Near-infrared (NIR) spectroscopy is a useful technique for quantitative measurements of intact tablets, but it suffers from limitations due to the fact that changes in the physical properties of a sample strongly affect the recorded spectrum. In this work, time-resolved transmission NIR spectroscopy was utilized to conduct quantitative measurements of intact tablets. The technique enables separation of the absorption properties of the sample from the scattering properties and can therefore handle changes of the physical parameters of the samples in a better way than conventional NIR transmission spectroscopy. The experiments were conducted using a pulsed Ti:sapphire laser coupled into a nonlinear photonic crystal fiber as light source. The light transmitted through the sample was measured by a time-resolving streak camera. A comparison of the results from the time-resolved technique with the results from conventional transmission NIR spectroscopy was made using tablets containing different concentrations of iron oxide and manufactured with different thicknesses. A PLS model made with data from the time-resolved technique predicted samples 5 times better than a PLS model made data from the conventional NIR transmission technique. Furthermore, an improvement to predict samples with physical properties outside those included in the calibration set was demonstrated.

Spectroscopic studies of wood-drying processes

“…In order to further elucidate the interplay between scattering and absorption, time-resolved measurements of the photon history in the wood for the two wavelengths would provide independent information on the scattering of the material and the liquid water contents. Such measurements can be performed using white light [6,9], capturing the full spectrum, or employing a number of pulsed diode lasers selected at appropriate wavelengths [24]. …”

“…However, the application of this method is not straightforward for natural materials such as wood, since the fact that they are inhomogeneous and porous also means that they are highly scattering, making the optical pathlength through the sample undefined. This situation is common in medical optics, where scattering and absorption are intertwined [5], as is also the case in analytical spectroscopy of pharmaceutical preparations [6]. Different techniques for handling multiple scattering of light have been developed for assessing the concentration of liquid and solid absorbing constituents.…”

<title>Gas in scattering media absorption spectroscopy - GASMAS</title>

“…Our efforts have recently focused on the study of pharmaceutical tablets [13][14][15]. It is of considerable interest to be able to measure constituent concentrations in tablets without the need of dissolving them.…”

Transmission Near-Infrared (NIR) and Photon Time-of-Flight (PTOF) Spectroscopy in a Comparative Analysis of Pharmaceuticals

“…PTOFS is becoming increasingly popular in broadband instruments. [21][22][23] The technique has been used specifically for the inspection of tablets [24][25][26] and powders. 27 Khoptyar et al 26 have recently shown feasibility of spectroscopic evaluation of tablet concentration on the basis of their PTOFS absorption spectra.…”