Spectral analysis methods

Principles and Characteristics Mass-spectral analysis methods may be either indirect or direct. Indirect mass-spectral analysis usually requires some pretreatment (normally extraction and separation) of the material, to separate the organic additives from the polymers and inorganic fillers. The mass spectrometer is then used as a detector. Direct mass-spectrometric methods have to compete with separation techniques such as GC, LC and SFC that are more commonly used for quantitative analysis of polymer additives. The principal advantage of direct mass-spectrometric examination of compounded polymers (or their extracts) is speed of analysis. However, quite often more information can be... 

For a quantitative analysis or classification of biological or medical problems by means of Raman spectroscopy the application of multivariate spectral analysis methods is required. These multivariate methods allow one to extract diagnostic, chemical, and morphological relevant information out of the complex Raman spectrum and must be applied due to the high amount of similar spectral features. 

Kuzyakov Y.Y., Semenenko K.A., Zorov N.B., Spectral Analysis Methods, Moskovskii Gos. Univ., Moseow 1990. 

For more information on fitting model expressions to peak-shaped experimental curves you might want to consult the review by Fraser Suzuki in ]. A. Blackburn, ed., Spectral Analysis Methods and Techniques, Dekker, 1970, from which some of the above discussion was abstracted. 

D. W. Noid, M. L. Koszykowski, and R. A. Marcus, Spectral analysis method of obtaining molecular spectra from classical trajectories, J. Chem. Phys. 67 404 (1977) M. L. Koszykowski, D. W. Noid, and R. A. Marcus, Semiclassical theory of intensities of vibrational fundamentals, overtones, and combination bands, J. Phys. Chem. 86 2113 (1982) D. W. Noid, M. L. Koszykowski, and R. A. Marcus, Quasiperiodic and stochastic behavior in molecules, Ann. Rev. Phys. Chem. 32 267 (1981). 

We studied the XANES spectra of an over exchanged Cu-ZSM-5-164 and an underexchanged Cu-ZSM-5-59. Both catalysts were treated in He flow at 773 K, 30 minutes for 164% and 45 minutes for 59% exchanged samples, before He was replaced by 1% NO/Nj. Their corresponding XANES spectra are shown in Fig. 4 and Fig 7. The most profound feature in these spectra is the difference in Cu(I) ls 4p transition intensity before and after the admission of NO. For Cu-ZSM-5-164, about 70% of the copper ions were reduced to cuprous ions in He flow, using the aforementioned spectral analysis method. The Cu(I) percentage concentration decreases rapidly to 35% after the gas switch and maintains at this level during 60 minutes of NO decomposition catalysis at 773 K. For Cu-ZSM-5-59, virtually all the copper ions were auto-reduced to Cu(I) in He flow. The static... 

As with any spectral analysis method, a group of spectral lines comprises a fingerprint of the unknown element. If more than one element is present, as is generally the case, spectral overlap may occur and the analyst must use care to avoid error. In... 

Smith, L.E., Anderson, K.K., Ressler, J.J. et al. (2010). Time-spectral analysis method for spent fuel assay using lead slowing-down spectroscopy, IEEE Trans. Nucl. Sci. 57, 2230-2238. 

This chapter and Chapter 5 will attempt to demystify some of the more basic tenets of chemometric spectral analysis methods. The intent is not to completely explain all the complex mathematics behind the techniques (although the equations are provided in almost all cases). Instead, they are designed to give a basic understanding of how and why the mathematics work in order to properly apply them to solving analytical problems. These chapters may also serve as a foundation to learning more about chemometrics and, hopefully, to lead the reader to other sources of information. 

In addition to the conventional spectral analysis methods and chemometrics, two-dimensional (2D) correlation spectroscopy has recently been introduced to NIR spectroscopy (4,12-16). In this method spectral peaks are spread over a second dimension to simplify the visualization of complex spectra consisting of many overlapped bands and to explore correlation between the bands. There are two kinds of 2D correlation spectroscopy used in NIR spectroscopy. One is statistical 2D correlation proposed originally by Barton et al (16). This method employs cross-correlation based on the least-squares linear regression analysis to assess spectral changes in two regions, such as the NIR and mid-IR regions, that arise from variations in sample composition (16). In another 2D correlation spectroscopy proposed by Noda (12, 13), 2D spectra are constructed from a set of spectral data collected from a system under an external physical perturbation, which induces selective alterations in spectral features. 

Conventional spectral analysis methods used in NIR spectroscopy are summarized as follows. 

Y. Ozaki, S. Sasic, J.H. Jiang. How can we unravel complicated near infrared spectra — Recent progress in spectral analysis methods for resolution enhancement and band assignments in the near infrared region. J Near Infrared Spectrosc 9 63, 2001. 

K. Murayama, B. Czamik-Matusewicz, Y. Wu, R. Tsenkova, Y. Ozaki. Comparison between conventional spectral analysis methods, chemometrics, and two-dimensional correlation spectroscopy in the analysis of near-infrared spectra of protein. Appl Spectrosc 54 978, 2000. 

Chemometrics is often defined as the application of statistics and mathematics to the analysis of chemical data. Without arguing the sufficiency of this definition, it is safe to say that the application of multivariate statistical and mathematical spectral analysis methods to near-infrared (NIR) data provides an intriguing set of advantages absent in univariate analysis of NIR data. Foremost of these advantages are the abilities to preprocess NIR spectra for removal of complex background signals, perform multianalyte calibration and calibration in the presence of multiple changing chemical... 

Samarakoon, T., Shiva, S., Lowe, K., Tamura, P, Roth, M.R. and Welti, R. (2012) Ara-bidopsis thahana membrane hpid molecular species and their mass spectral analysis. Methods Mol. Biol. 918, 179-268. 

Recent progress in IR and Raman spectroscopy may be summarised as follows (i) challenging of the ultra world ultra-fast, ultra-small, and ultra-thin and (ii) progress in spectral analysis methods such as 2D correlation spectroscopy, chemometrics, and new calculation methods for normal vibrations. 

D. W. Noid, M. L. Koszykowski, and R. A. Marcus, A spectral analysis method of obtaining molecular spectra from classical trajectories, J. Chem. Phys. 67 404 (1977). 

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