NIR-FT-Raman spectroscopy

Schulz, H., Baranska, M., and Baranski, R., Potential of NIR-FT-Raman spectroscopy in natural carotenoid analysis. Biopolymers, 11, 212, 2005. 

M. Baranska, H. Schulz, R. Siuda, et al. Quality control of Harpagophytumprocumbens and its related phytop-harmaceutical products by means of NIR-FT-Raman spectroscopy, Biopolymers, 77, 1-8 (2005). 

Excitation of Raman spectra in the near-infrared range excludes fluorescence of samples and impurities, which used to mask the Raman spectra of real life products. The very low intensity of Raman spectra in this range, which is proportional to the fourth power of the frequency, can be overcome by interferometers which employ the Jacquinot and multiplex advantage. Special features of NIR FT Raman spectroscopy are described in Sec. 3.5.5. 

If the spatial resolving power has to be high, then the Raman radiation must be observed through microscope objectives (Fig. 3.5-10 b). Unfortunately, these objectives have a somewhat lower optical conductance than the regular sample arrangement (Schrader, 1990). As a result, the observed Raman spectrum is also considerably weaker. A microscope may be connected to the spectrometer by a mirror system or by optical fibers, as shown in Fig. 3.5-10 b. Optical fibers are e.specially useful for NIR FT Raman spectroscopy, because the transmission of the fibers may be at its maximum exactly in the range of a Raman spectrum excited by a Nd YAG laser (Fig. 3.3-5). 

In the region of NIR FT Raman spectroscopy, at F = 5000...10000 cm , substances with X-H bonds (X = any element) show overtones and combinations of the normal frequencies. They may have considerable intensity as demonstrated by Fig. 3.5-3 with the NIR absorption spectra of liquid H2O, D2O, ethanol, and cyclohexane. The linear decadic absorption coefficient a of water at a Raman shift of about 2500 cm is of the order of 10. The transmission of a layer of d = 1 cm is given by ... 

This example illustrates that measurements of absolute scattering coefficients and quantitative analyses are somewhat more difficult in NIR FT Raman spectroscopy than in the visible region, where absorption can usually be neglected. In any case, it is necessary to carefully calibrate (D Orazio and Schrader, 1974, 1976) the spectral sen.sitivity of the instrument. 

Joint interpretation of the IR and Raman spectra of biomolecules, which frequently lack symmetry properties, may afford more extensive information concerning the primary, secondary and tertiary structure, than does the interpretation of one type of spectrum only. Many systems can only be investigated in aqueous solution, a good solvent for Raman spectroscopy. The technique of resonance Raman spectroscopy facilitates investigations of pigments and the NIR FT Raman spectroscopy allows the investigation of nearly all samples which has not been possible before due to absorption and fluorescence. Spectra of biomolecules are exhaustively discussed in Sec. 4.7. Here only some general features are discussed. 

The new NIR FT Raman spectroscopy now allows the investigation of food (Keller et al., 1993). Fig. 4.1.20 shows typical Raman spectra of food components carbohydrates, proteins, and lipids. Fig. 4.1-20C shows the Raman spectrum of a banana with the out-of-phase and in-phase vibrations of the C-O-C groups of the carbohydrates at about 1100 and 850 cm. Fig. 4.1-20B, a Raman spectrum of turkey breast shows the amide I and III bands and some bands which can be directly assigned to amino acids. The Raman spectra of lipids allow the determination of the amount of cis and trans disubstituted C=C bonds Fig. 4.1-20A, butter (Keller et al., 1993). NIR Raman spectroscopy has good chances as tool for the investigation of living tissues, especially in medical diagnostics (Keller et al., 1994 Schrader et al., 1995). 

Lewis D M, ShenX M and Tapley KN, NIR FT-Raman spectroscopy for monitoring the synthesis of azo dyes , Mikrochimica Acta [Supplement , 1997,14, 751-754. 

A.M. Davidson, C.F, Mellot, J. Eckert A.K. Cheetham (2000). J. Phys. Chem. B, 104, 432-438. An inelastic neutron scattering and NIR-FT Raman spectroscopy study of chloroform and trichloroethylene in faujasites. 

The potential of NIR FT-Raman spectroscopy for the investigation of zeolites (vanadyl-containing MFI, TS-1) as well as alumophosphate-based molecular sieves (AEI, CHA, CEO) are described. In Raman spectra of template containing samples bands of the organic species dominate. By dispersive Raman microscopy a spatial distribution in a CoAPO-34 crystal is observed. The Raman spectra allow a very rapid and sensitive detection of anatase formed during thermal treatment of as-synthesised titanium-containing zeolites. Different vanadium species are detected in vanadium-containing ZSM-5. 

New approaches to analyze essential oils by vibrational spectroscopy using attenuated re ec-tion (AIR) IR spectroscopy and NIR-FT-Raman spectroscopy have recently been published by Baranska et al. (2005) and numerous papers cited therein. The main components of an essential oil can be identi ed by both spectroscopic techniques using the spectra of pure oil constituents as references. The spectroscopic analysis is based on characteristic key bands of the individual constituents and made it, for example, possible to discriminate the oil pro les of several eucalyptus species. As can be taken from this paper, valuable information can be obtained as a result of the combined application of ATR-IR and NIR-FT-Raman spectroscopy. Based on reference GC measurements, valuable calibration equations have been developed for numerous essential oil plants and related essential oils in order to quantify the amount of individual oil constituents applying different suitable chemometric algorithms. Main advantages of those techniques are their ability to control the quality of essential oils very fast and easily and, above all, their ability to quantify and analyze the main constituents of essential oils in situ, that means in living plant tissues without any isolation process, since both techniques are not destructive. 

In spite of these considerations MIR proved to be by far the most effective of a range of techniques studied in a wide ranging assessment of recognition methods that also considered NIR, FT Raman spectroscopy. Pyrolysis Mass Spectrometry, Pyrolysis Infrared Spectroscopy and Laser Induced Emission Spectral analysis [6]. 

Miller et al. [79] analyzed rigid polyurethane foams by NIR spectroscopy. Further studies by Miller et al. [80-82] included the use of factor analysis to analyze polyester urethane urea block copolymers, and the determination of physical properties of reaction-injected-molded polyurethane by NIR-FT-Raman spectroscopy. 

Miller, C.E., et al., Determination of Physical Properties of Reaction-Injection-Molded Polyurethanes by NIR-FT-Raman Spectroscopy. Appl. Spectrosc., 1990.44 1297-1300. 

J Sawatski, D Charmot, B Amram, C Macron, J-P Huvenne, M Agnely, A Simon, C Lehner, J Asua, J Leiza, P Armitage. NIR FT-Raman spectroscopy On-line control of an emulsion polymerization for the laboratory to the production plant. In A Heynes, ed. Proceedings of the XVIth International Conference on Raman Spectroscopy. Chichester Wiley, 1998, pp 728-729. 

B Schrader, B Dippel, S Fendel, S Keller, T Lochte, M Riedl, R Schulte, E Tatsch. NIR FT Raman spectroscopy—A new tool in medical diagnostics. J Mol Struct 408/409 23-31, 1997. 

S Wessel, M Gniadecka, GBE Jemec, HC Wulf. Hydration of human nails investigated by NIR-FT-Raman spectroscopy. Biochim Biophys Acta 1433 210-216, 1999. 

M Gniadecka, HGM Edwards, JP Hart Hansen, OF Nielsen, DH Christensen, SE Guillen, HC Wulf. NIR-FT Raman spectroscopy of the mummified skin of the Alpine Iceman, Qilakitsoq Greenland mummies and Chiribaya mummies from Peru. J Raman Spectrosc 30 147-153, 1999. 

Kendra et al. [386] have recently reviewed the use of NIR FT-Raman spectroscopy in the study of many (co)polymers and blends, both qualitatively and quantitatively. For an overview of FT-Raman of elastomers, cfr. ref. [406],... 

Applications of UV Raman are in the fields of biological and materials science, biochemistry, forensic sciences, etc., whereas application areas for both NIR and VIS Raman are polymers, polymerisation, paints, dyestuffs, pharmaceutical materials, alkaloids, minerals, explosives, multilayer films, hard disk quality control, etc. Especially NIR FT Raman spectroscopy finds promising applications in various fields, from latex systems [180] to textiles [181], Hendra et al. [182] and Schrader [183] have recently described application of NIR FT-Raman spectroscopy in the polymer industry. 

Water in skin samples can be characterized by NIR-FT-Raman spectroscopy. The high wavenumber region from 2500 to 3500 cm measures the total amount of water. A broad band with a maximum at about 180 cm gives an estimate of the presence of water not bound to biomolecules, free water with a bulk-like liquid water structure. In the low-wavenumber region... 

D. (1973) Vibrational spectra of some carotenoids and related linear polyenes - Raman spectroscopic study. /. Am. Chem. Soc., 95 (14), 4493-4501. Schulz, H., Baranska, M, and Baranski, R. (2005) Potential of NIR-FT-Raman spectroscopy in natural carotenoid analysis. Biopolymers, 77 (4), 212-221. Baranska, M., Schutze, W, and Schulz, H. (2006) Determination of lycopene and /J-carotene content in tomato fruits and related products Comparison of FT-Raman, ATR-IR, and NIR spectroscopy. Anal Chem., 78 (24), 8456-8461. 

Schulz, H., Schrader, B., Quilitzsch, R., and Steuer, B. (2002) Quantitative analysis of various citrus oils by ATR/FT-IR and NIR-FT Raman Spectroscopy Appl Spectrosc., 56 (1), 117-124. 

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