Near-infrared diffuse reflectance spectroscopy NIRS

Various optical detection methods have been used to measure pH in vivo. Fluorescence ratio imaging microscopy using an inverted microscope was used to determine intracellular pH in tumor cells [5], NMR spectroscopy was used to continuously monitor temperature-induced pH changes in fish to study the role of intracellular pH in the maintenance of protein function [27], Additionally, NMR spectroscopy was used to map in-vivo extracellular pH in rat brain gliomas [3], Electron spin resonance (ESR), which is operated at a lower resonance, has been adapted for in-vivo pH measurements because it provides a sufficient RF penetration for deep body organs [28], The non-destructive determination of tissue pH using near-infrared diffuse reflectance spectroscopy (NIRS) has been employed for pH measurements in the muscle during... 

R. Mehrota, A. Gupta, J. Tewari, S. P. Varma. Estimation of total sugar and reducing sugar in molasses using near infrared diffused reflectance spectroscopy. In Near Infrared Spectroscopy. A. M. C. Davies, R. K. Cho, eds, NIR Pubhcations, UK, 2002, 207-211. 

Murray, L, in The NIR Spectra of Homologous Series of Organic Compounds in Near- Infrared Diffuse Reflectance/transmittance Spectroscopy, Hollo, J., Kaffka, K.J., and Gonczy, J.L. (Eds.), Akademiai Kiado, Budapest, 1987, pp. 13-28. 

B. Barabas. Comparison of measurability of two produces of high protein content. In Near Infrared diffuse reflectance/transmittance spectroscopy. Proceedings of the International NIR/NFF conference, Budapest, Hungary, May 12-16,1986. J. Hollo, et al co-eds. Akademiai Kiado, Budapest. 1987, p. 169-176. 

Guiader, M., Cheese and meat analysis by NIR, International Near Infrared Diffuse Reflectance/Transmittance Spectroscopy Conference, Budapest, Hungary, May 1986. 

The value of computing derivative spectra to correct for non-linear baseline signals is frequently exploited in reflectance spectrometry. Rapid measurement of the chemical composition of materials and products by diffuse reflectance spectroscopy in the near-infrared (NIR) region (800-2600 nm) is routine in many industries. Because most bulk materials are not transparent the mode of measurement is generally reflectance. For powder samples the intensity of... 

Diffuse reflectance spectroscopy (DRS) has been frequently employed in UV-Vis spectroscopy of zeolites (cf. Volume 4, Chapter 4 of the present series). More recently, it became also popular in IR investigations (cf., e.g., [160, 161]). The DRIFT technique is advantageous because it is successfully applicable not only in the mid infrared but also in the near infrared (NIR) region of 4000-10,000 cm where the transmission technique usually fails because of severe scattering through the absorbent particles. The NIR range, however, is very important with respect to the study of overtone and combination modes of vibrations. Moreover, diffuse reflectance IR experiments can be carried out not only with pressed wafers as in transmission spectroscopy, but also with zeolite pow-... 

Near-infrared reflectance spectroscopy (NIRS) is an analytical technique that correlates diffusely... 

Another type of transflectance spectroscopy that is commonly used for measurements of near-infrared spectra falls somewhere between specular reflection and diffuse reflection spectroscopy (see Chapter 16). Because overtone and combination bands are weak, anomalous dispersion is usually negligibly small in the near infrared. It is quite common for the NIR spectra of liquids to be measured by transflection using the same optical geometry used for diffuse reflection. In this case, the sample is loaded in a cell whose rear face is a ceramic disk. Radiation that has passed through the sample is scattered back through the sample, emerges from the window, and is focused onto the detector. This is a particularly useful way of measuring the spectrum of turbid samples, such as milk. 

Near-infrared (NIR) spectra are rarely used to identify materials, but NIR spectroscopy has nonetheless assumed a role of great importance for contemporary analytical chemists. Near-infrared (NIR) diffuse reflection spectroscopy became of great importance in the 1970s, when it was shown that the concentration of protein, oil, and water... 

Intensified metabolic control, especially in case of diabetes, demands minimal-invasive or non-invasive methods of analytical measurement. For this goal, a method has been developed to measure the blood glucose content in vivo, in direct contact with the skin, by means of diffuse reflection near infrared (NIR) spectroscopy on the basis of multivariate calibration and neural networks (Muller et al. [1997] Fischbacher et al. [1997] Danzer et al. [1998]). Because no patients with any standard blood glucose value are available in principle, a method of indirect calibration has... 

One indication of the developing interest in PATs in the pharmaceutical area is the number of book chapters and review articles in this field that have appeared in the last few years. Several chapters in The Handbook of Vibrational Spectroscopy3 are related to the use of various optical spectroscopies in pharmaceutical development and manufacturing. Warman and Hammond also cover spectroscopic techniques extensively in their chapter titled Process Analysis in the Pharmaceutical Industry in the text Pharmaceutical Analysis.4 Pharmaceutical applications are included in an exhaustive review of near-infrared (NIR) and mid-infrared (mid-IR) by Workman,5 as well as the periodic applications reviews of Process Analytical Chemistry and Pharmaceutical Science in the journal Analytical Chemistry. The Encyclopedia of Pharmaceutical Technology has several chapters on spectroscopic methods of analysis, with the chapters on Diffuse Reflectance and Near-Infrared Spectrometry particularly highlighting on-line applications. There are an ever-expanding number of recent reviews on pharmaceutical applications, and a few examples are cited for Raman,7 8 NIR,9-11 and mid-IR.12... 

The application of NIR spectroscopy has been further stimulated by the development of NIR diffuse reflectance techniques which are widely used in the analysis of agricultural, pharmaceutical, biochemical and synthetic polymer materials (Siesler, 1991). The rapidly increasing use of NIR spectroscopy is illustrated in the book Making Light Work Advances in Near infrared spectroscopy , edited by Murray and Cowe (1992) as well as in the Handbook of Near-Infrared Analysis by Bums and Ciurcak (1992). 

Ritchie, G. E., Gehrlein, L., and Ciurczak, E. W. Simultaneous development, validation and implementation of a near-infrared (NIR) diffuse reflectance spectroscopic identification method for pharmaceutically active and inactive (placebo) clinical dosage forms. In Pittsburgh Conference of Analytical Chemistry and Applied Spectroscopy, March 2000, New Orleans, LA. 

Several spectroscopic and nonspectroscopic techniques may be used to study the bonding nature of the adsorbate to the surface [2a, 4]. In the first case we want to emphasize the importance of diffuse reflectance techniques for absorption and emission studies in the ultraviolet (UV), Visible (Vis), and near infrared (NIR) spectral ranges. X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. In the second group, we refer the heat adsorption and the isotherm adsorption techniques, among others. 

This study was prompted by a report on the rapid determination of lignocellulose by diffuse reflectance Fourier transform infrared reflectance (FT/IR) spectroscopy [1]. Although the results of that study were good, the claims by the promoters of near-infrared (NIR) instrumentation suggested that the latter might produce equally good results in less time and with less sample preparation. 

Molecular weight of recycled HDPE as measured by size-exclusion chromatography can be correlated with diffuse reflectance near- and mid-infrared spectroscopy (NIR/MIR). The RMSEP obtained with MIR data was 360 and with NIR data was 470. The degree of crystallinity determined by DSC can also be correlated to the spectra. The prediction ability of this model was poor in the 1100 to 1900 nm region, however the 2000 to 2500 nm region yielded better results. Four PC factors explained the most of the variance in the spectra and the RMSEP was 0.4% wt. [51]. 

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