Near infrared spectrum

Fig. 36.2. Raw data near-infrared spectra of a food product with different X-content.

In short, near-infrared spectra arise from the same source as mid-range (or normal ) infrared spectroscopy vibrations, stretches, and rotations of atoms about a chemical bond. In a classical model of the vibrations between two atoms, Hooke s Law was used to provide a basis for the math. This equation gave the lowest or base energies that arise from a harmonic (diatomic) oscillator, namely ... 

W.R. Hruschka and K. Norris, Least squares curve fitting of near-infrared spectra predicts protein and moisture content in ground wheat, Appl. Spectrosc., 36, 261-265 (1982). 

M. Chaoxiong and S. Xueguang, Continuous wavelet transform applied to removing the fluctuating background in near-infrared spectra, J. Chem. Inf. Comput. Sci., 44, 907-911 (2004). 

S. Wold, H. Antti, F. Lindgren and J. Ohman, Orthogonal signal correction of near infrared spectra, Chemom. Intell. Lab. Syst, 44, 175-185, (1998). 

P. Caceres-Alonso and A. Garcfa-Tejedor, Non-supervised neural categorisation of near infrared spectra. Application to pure compounds, J. Near Infrared Spectrosc., 3, 97-110 (1995). 

LA. Cowe, J.W. McNicol and D.C. Cuthbertson, A designed experiment for the examination of techniques used in the analysis of near-infrared spectra. Part 2 Derivation and testing of regression models. Analyst 110,1233-1240 (1985). 

Finally, the use of PAT should not be limited to existing processes and products but is especially attractive in the R D and scale-up of new processes and products. PAT is especially effective in scale-up. As PAT involves consideration of all monitored variables and not only an empirical selection of some of those variables, and since in-process monitoring techniques are normally multiparametric (e.g., near-infrared spectra of a whole sample), they will be more suited to capture scale effects present in the sample s matrix that show up clearly in a consolidated multivariate analysis of quality and operating variables, thus helping the skillful engineer or scientist to pinpoint and solve scale-up problems thus resulting in a much faster process prototyping and scale-up. 

Field, M. (1995) Interpretation of near infrared spectra of silages in relation to predicted and actual feeding value. Ph.D. thesis. University of Wales, Aberystwyth, 336 pp. 

To illustrate mean centering, near-infrared spectra of organic mixtures are plotted in Fipare 3.22 7, with the mean-centered spectra shown in Figure 5.22b. The man spectrum (overall shape) has been removed from all the spectra and the relative differences in intensity at the various wavelengths arc easier to discou. 

Figure 3.22. Near-infrared spectra of organic mixtures before (a) and after (b) mean centering.

FIGURE 5.26. Near-infrared spectra of the four pure components for DLCS Example 2. 

Vilas, F., Jarvis, K. S. and Gaffey, M. J. (1994) Iron alteration minerals in the visible and near-infrared spectra of low-albedo asteroids. Icarus, 109, 274-283. 

I2]. The substantial solubilities of these compounds in chloroform and other less polar organic solvents are in agreement with their formulation as nonelectrolytes. In methanol at 25° C., the molar conductivities of 166 and 167 ohm-1 for [Ni-(NH2CH2CH2S-CH3)2I2] and [Ni(NH2CH2CH2S-CH2C6H5)2I2], respectively, are characteristic of di-univalent electrolytes in this solvent, indicating almost complete solvolysis of the coordinated iodide ions in this relatively polar solvent. Decomposition of these complexes was observed upon dissolving in water. Visible and near-infrared spectra results are also consistent with structure VI. 

Figure 6 Representation near infrared spectra in matrix form.

Fig, 3. Transient absorption spectra of peridinin in methanol recorded in the visible (a) and the near-infrared (b) spectral regions after excitation at 490 nm in methanol (full squares) and at 535 nm in ethylene glycol (open squares). The transient absorption spectra in the visible region are normalized to the ESA maximum, while the near-infrared spectra are normalized to a maximum of the ICT emission. 

The status of WR abundance analyses through IAU Symposium 99 was very well summarized by Willis (1982) see also Linda J. Smith and Willis (1982,1983). Since then, additional information on the He/H ratios has been provided by Conti, Leep, and Perry (1983), while substantial progress on modeling the He spectra has been contributed by Hamann and Schmutz (1987 and references therein) and by Hillier (1987a, b). The WC stars are special, as the only well-defined class of massive stars showing us the products of helium burning. Currently, improved determinations of their C/He ratios are being made by Lindsey F. Smith and Hummer (1987) from near infrared spectra, and by Torres (1987) optically. 

NMR spectra were taken in deuteriochloroform solution, using a Varian HA100 spectrometer. Thermal measurements were made with a Perkin-Elmer DSC IB differential scanning calorimeter at 40°C/min. Near-infrared spectra were measured in carbon disulfide solution with a Beckman DK 2A spectrophotometer. Gas-chromatographic analyses of reaction mixtures were carried out after conversion of the phenols to trimethylsilyl ethers by reaction with bis (trimethylsilyl) acetamide. 

Figure 6 Near-infrared spectra of wheat fractions (Wetzel, D. L. Mark, H. "Spectroscopic Determination of Cellulose as Criterion of Flour Purity with Respect to Bran", American Association of Cereal Chemists 62nd Annual Meeting, San Francisco, CA 1977).

Hruschka, W.R. and Norris, K., Least Squares Curve Fitting of Near-Infrared Spectra Predicts Protein and Moisture Content in Ground Wheat Appl. Spectrosc. 1982, 36, 261-265. 

Arnold MA, Burmeister JJ, Small GW. Phantom glucose calibration models from simulated noninvasive human near-infrared spectra. Analytical Chemistry 1998, 70, 1773-1781. 

Arnold MA, Small GW, Xiang D, Qui J, Murhammer DW. Pure component selectivity analysis of multivariate calibration models from near-infrared spectra. Analytical Chemistry 2004, 76, 2583-2590. 

Noninvasive Near-Infrared Spectra Collected Across the Rat Skin... 

Although composed of weak and overlapping spectral features, near-infrared spectra can be used to extract analytical information from complex sample matrices. Chemical sensing with in-line near-infrared spectroscopy is a general technique that can be used to quantify multiple analytes in complex matrices, often without reagents or sample pretreatment.7-9 Applications are widespread in the food sciences, agricultural industry, petroleum refining, and process analytical chemistry.10-13 These activities demonstrate that near-infrared spectroscopy can provide selective and accurate quantitative measurements both rapidly and nondestructively. 

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