Near-infrared spectroscopy NIR

Originally a laboratory curiosity, the applications of NIR in the industrial environment have burgeoned miraculously in the last five years. This expansion owes more to the greater understanding of chemometric techniques for data analysis, and the development of superior optical fibres for the transmission of NIR radiation, than to any breakthrough in NIR science itself. 

Essentially, NIR spectra are the result of vibrational overtones. The fundamental vibrations can normally be observed in the mid-infrared region, where they are much more intense. Overtones involving the 

Recently, NIR has been used for raw material confirmation, quantitative analysis of mixtures, protein assays and structure-activity relationships. A selection of recent work in the field is contained in [3]. 

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Near-infrared Spectroscopy. Near-infrared spectroscopy (NIRS) uses that part of the electromagnetic spectrum between the visible and the infrared. This region has the advantage that the instrumentation is nearest to visible instrumentation. Signals in the near-infrared come not from the fundamental vibrations of molecules but from overtones. As... 

A. Villringer, J. Planck, C. Hock, L. Schleinkofer, and U. Dirnagl. Near infrared spectroscopy (nirs) a new tool to study hemodynamic changes during activation of brain function in human adults. Neuroscience Letters, 154 101-104, 1993. 

P. Zaramella, F. Freato, A. Amigoni, s. Salvadori, P. Marangoni, A. Suppjei, B. Schiavo, and C. Lino. Brain auditory activation measured by near-infrared spectroscopy (nirs). Pediatric Research, 49 213-219, 2001. 

Near-field scanning optical microscope (NSOM), 16 501-503 Near-infrared absorbing dyes, 9 341 Near-infrared spectroscopy (nir),... 

Near infrared spectroscopy (NIRS), a technique based on absorption and reflectance of monochromatographic radiation by samples over a wavelength range of 400-2500 run, has been successfully applied for food composition analysis, for food quality assessment, and in pharmaceutical production control. NIRS can be used to differentiate various samples via pattern recognitions. The technique is fast and nondestructive method that does not require sample preparation and is very simple to use compared too many other analytical methods such as HPLC. The drawback of NIRS, however, is that the instrument has to be calibrated using a set of samples typically 20-50 with known analyte concentrations obtained by suitable reference methods such as FIPLC in order to be used for quantitative analyses. Simultaneous quantification of the... 

Near-Infrared Spectroscopy (NIR) as a PAT Tool in the Chemical Industry Added Value and Implementation Challenges... 

Eor means of determination and quantification of the material porosity, different methods like mercury intrusion porosity, nitrogen gas adsorption, or inverse-size exclusion chromatography (ISEC) have been established and are nowadays routinely employed for that purpose. As an alternative to these well-known methods, a new approach based on near-infrared spectroscopy (NIR) for the characterization of monoliths is introduced in this chapter. 

Despite the fact that near infrared spectroscopy (NIR) has been used industrially for decades [36], there has been hesitance to accept and trust new process analytical measurement technologies as equivalent or superior to traditional methods. For example, when a discrepancy between online NIR and laboratory analyses is observed, it is rare that the destructive reference methods are ever targeted as the source of error, despite the fact that NIR is often the more precise method. The hesitance to trust more advanced, multivariate tools (which are perhaps less directly understood) has certainly been a detriment to progress in deploying PAT. 

A typical illustration of a PAT approach to quality improvement is the use of near-infrared spectroscopy (NIRS) to qualify excipients and active principles just before they enter the production process, for example, in dispensing. As discussed in the next part, near-infrared (NIR) spectra are informative about product structure and overall quality. Because with substances such as excipients the quality range was investigated at some time in the past and fixed into a calibration, NIR measurement can provide simultaneous nondestructive confirmation of the predominant physical and chemical parameters. This is an effective method of reducing uncertainties about possible causes of failure or poor quality during production. Each time a given excipient fails its quality requirements at the moment of use, immediate action can be taken. Control is possible before the risk of failure is increased. Such an approach is complementary to container-wise identification of materials on delivery to a warehouse. 

The best way to elucidate the reaction path is to follow the evolution of as many independent species and functional groups as possible. For example, analysis of the epoxy-amine reaction following the simultaneous evolution of epoxy and primary amine groups by near infrared spectroscopy (NIR) simultaneous determination of the conversion of double bonds belonging to unsaturated polyester (UP) and styrene (S) using FTIR, as shown in Fig. 5.13 (Yang and Lee, 1988) determination of the evolution of the concentration of free radicals using ESR, as shown in Fig. 5.14 (Tollens and Lee, 1993). 

Carbon Quantification by Near-Infrared Spectroscopy (NIRS) 677... 

Near-infrared spectroscopy (NIRS) has become a very popular technique for a wide range of analysis in various industries. The usefulness of this technique is mainly attributed to allowing the rapid analysis of bulk materials with a simple manipulation procedure. On the other hand, improvements of instrumentation, and specially the development of chemometric software, have contributed to the tremendous expansion of and to the current state of popularity of this technique (Bokobza, 2002). 

Near-infrared spectroscopy (NIRS) in hydrocarbon analysis... 

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