Fourier-transformed near infrared FT-NIR

Recently Benali et al. (2004) reported the development of a new laboratory-made system that allows the combination of rheometric (Alessi et al, 2005) and spectroscopic (Fourier-transform-near infrared (FT-NIR) spectroscopy) measurements for reactive polyurethane materials along the lines of these principles. 

Finally, a quick, non-destructive method, based on Fourier transform near-infrared (FT-NIR) spectroscopy for egg content deteimination of dry pasta was presented by Fodor et al. (2011) with good results. 

Abstract Fourier-transform near infrared (FT-NIR) spectroscopy in combination with a... 

The manual sorting method is labor intensive and requires operators to monitor an assembly line and sort out clear plastic bottles (PET) from the milk containers (HDPE) and colored plastic containers (LDPE, PP, PVC). The automated method can employ one of several analytical techniques, including X-ray fluorescence, mass spectroscopy, Fourier Transform Near Infrared (FT-NIR) spectroscopy, Fourier Transform Medium Infrared (FTIR) spectroscopy, or tribo-electric analysis, on the recycled plastic materials. The state of Rhode Island has a single stream process to sort out the recycled materials with optical sorting technology. The recycled materials include cardboard, paper, glass, metal, and plastics (Rhode Island 2013). 

Fourier transform near-infrared (FT-NIR) spectrometers produce reflection spectra by moving mirrors. Once plagued by noise, modern FT-NIR spectrometers boast noise levels equivalent to grating-based instruments. FT-NIR spectrometers are full-spectrum instruments. 

Fourier Transform-Near infrared (FT-NiR). Only within the last 20 years has FT-NIR instrumentation (Fig. 4.1.14) become available. Even then, the first commercial instmments had a distinct disadvantage compared to grating-based scanning instruments. FT-NIR spectrometers employ an entirely different method for producing spectra. There is no dispersion involved. Energy patterns set up by an interaction with a sample and a reference and moving mirrors (or other optical components) produce sample and reference interferograms that are used to calculate the absorbance spectrum of the sample. 

Figure 4.1.14. The Bruker Matrix-E, a Fourier transform near-infrared (FT-NIR) spectrometer (Bruker Optics Inc., 19 Fortune Drive, Manning Park, BiUerica, MA 01821-3991) (A) illustrating the noncontact measuring concept and (B) mounted for analyzing sugarcane pulp passing underneath.

NIR Spectra were recorded on a Spectrum Identicheck Fourier transform near-infrared (FT-NIR) system (PerkinElmer Ltd., Beacconsfield Bucks, UK) with an IdentiCheck Reflectance Accessory (ICRA) with standard Spectrum Identicheck software including WC, version 2.0 to acquire and to process the data. WC was always applied using the default filter setting, which included a resolution filter. Measurements were carried out with an optical resolution of 16 cm over the spectral range 12,000 to 3,000 cm and 64 scans were co-added. A PbS detector was used. Spectralon was used as a background reference for solid samples. 

NIR reflectance spectra were collected using a Laser Precision PCM 4000 Fourier transform near-infrared (FT-NIR) spectrometer, equipped with CaF beam splitters and a thermoelectrically cooled PbSe detector. An Axiom difftise/specular reflectance attachment, set at 15" C, was used to collect the reflectance spectrum from each sample coupon. Each sample spectrum was the result of a 5 scan... 

An alternative approach for NIR hyperspectral imaging to the one described earlier is to use a Fourier transform near-infrared (FT-NIR) spectrometer. Since the design of FT-NIR microspectrometer is more similar to that of instruments... 

There are also more recent developments of other dual physio-chemical experimental methods. For example Durand et al (2006) presented a laboratory-made system that allows the coupling of dielectric analysis and Fourier-transform near-infrared spectroscopy (FT-NIR) to follow the cure of polyepoxy reactive systems. Complementary data are provided by the simultaneous dielectric analysis (the vitrification phenomenon) and near-infrared spectroscopic analysis (the extent of the reaction). 

Fats and Oils with emphasis on Trans Fatty Acids Using Fourier Transform Near Infrared Spectroscopy (FT-NIR), 40 855—867 (2005). 

Fourier transform mid-infrared (FTIR), near-infrared (FTNIR), and Raman (FT-Raman) spectroscopy were used for discrimination among 10 different edible oils and fats, and for comparing the performance of these spectroscopic methods in edible oil/fat studies. The FTIR apparatus was equipped with a deuterated triglycine sulfate (DTGS) detector, while the same spectrometer was also used for FT-NIR and FT-Raman measurements with additional accessories and detectors. The spectral features of edible oils and fats were studied and the unsaturation bond (C=C) in IR and Raman spectra was identified and used for the discriminant analysis. Linear discriminant analysis (LDA) and canonical variate analysis (CVA) were used for the disaimination and classification of different edible oils and fats based on spectral data. FTIR spectroscopy measurements in conjunction with CVA yielded about 98% classification accuracy of oils and fats followed by FT-Raman (94%) and FTNIR (93%) methods however, the number of factors was much higher for the FT-Raman and FT-NIR methods. 

There is a real chance of a breakthrough of Raman spectroscopy in routine analytics. Excitation of Raman spectra by near-infrared radiation and recording with interferometers, followed by the Fourier transformation of the interferogram into a spectrum -the so-called NIR-FT-Raman technique - has made it possible to obtain Raman spectra of most samples uninhibited by fluorescence. In addition, the introduction of dispersive spectrometers with multi-channel detectors and the development of several varieties of Raman spectroscopy has made it possible to combine infrared and Raman spectroscopy whenever this appears to be advantageous. 

In order to demonstrate the usefulness of the method, SERS spectra of indolino-spironaphthopyran (SPP, 4) and indolino-spironaphthoxazine (SPOX, 3) (see Scheme 7) were recorded at low concentration (10 7-10-8 A/) and their spectral characteristics analysed.48 Figure 8 shows the SERS spectrum of 4 in Ag colloids (spectrum a) along with the corresponding near-infrared Fourier transform (NIR-FT) Raman spectrum of the neat compound (spectrum b). Strong differences between the SERS and spontaneous Raman spectra are apparent. As stated above, these differences arise mainly from the particular orientation of the adsorbed spiropyran with to the metal surface in SERS experiments. 

Developments in Raman spectroscopy, with applications for colorants, have included resonance Raman, surface enhanced Raman spectroscopy (SERS), surface enhanced resonance Raman spectroscopy (SERRS) and near-infrared Fourier transform Raman spectroscopy (NIR-FT-Raman), with the latter technique discussed in the next section. 

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