Adapting Raman Spectra from Laboratory Spectrometers to Portable Detection Libraries

2013 ◽  
Vol 67 (2) ◽  
pp. 149-157 ◽  
Author(s):  
James C. Weatherall ◽  
Jeffrey Barber ◽  
Carolyn S. Brauer ◽  
Timothy J. Johnson ◽  
Yin-Fong Su ◽  
...  
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
First Generation ◽  
Near Infrared ◽  
Portable Detection ◽  
Intensity Response ◽  
Excitation Laser ◽  
Raman Spectral Data ◽  
Raman Spectral ◽  
Ft Raman

Raman spectral data collected with high-resolution laboratory spectrometers are processed into a format suitable for importing as a user library on a 1064 nm DeltaNu first generation, field-deployable spectrometer prototype. The two laboratory systems used are a 1064 nm Bruker Fourier transform (FT)-Raman spectrometer and a 785 nm Kaiser dispersive spectrometer. The steps taken to adapt for device-dependent spectral resolution, wavenumber shifts between instruments, and relative intensity response are described. Effects due to the differing excitation laser wavelengths were found to be minimal, indicating—at least for the near-infrared (NIR)—that data can be ported between different systems, so long as certain measures are taken with regard to the reference and field spectra.

scholarly journals Demonstrated Wavelength Portability of Raman Reference Data for Explosives and Chemical Detection

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Timothy J. Johnson ◽  
Yin-Fong Su ◽  
Kristin H. Jarman ◽  
Brenda M. Kunkel ◽  
Jerome C. Birnbaum ◽  
...  
Keyword(s):  
Near Infrared ◽  
Reference Data ◽  
Current Sensor ◽  
Data Sets ◽  
Reference Library ◽  
Wavelength Calibration ◽  
Intensity Response ◽  
Excitation Laser ◽  
Key Issues ◽  
Infrared Excitation

As Raman spectroscopy continues to evolve, questions arise as to the portability of Raman data: dispersive versus Fourier transform, wavelength calibration, intensity calibration, and in particular the frequency of the excitation laser. While concerns about fluorescence arise in the visible or ultraviolet, most modern (portable) systems use near-infrared excitation lasers, and many of these are relatively close in wavelength. We have investigated the possibility of porting reference data sets from one NIR wavelength system to another: We have constructed a reference library consisting of 145 spectra, including 20 explosives, as well as sundry other compounds and materials using a 1064 nm spectrometer. These data were used as a reference library to evaluate the same 145 compounds whose experimental spectra were recorded using a second 785 nm spectrometer. In 128 cases of 145 (or 88.3% including 20/20 for the explosives), the compounds were correctly identified with a mean “hit score” of 954 of 1000. Adding in criteria for when to declare a correct match versus when to declare uncertainty, the approach was able to correctly categorize 134 out of 145 spectra, giving a 92.4% accuracy. For the few that were incorrectly identified, either the matched spectra were spectroscopically similar to the target or the 785 nm signal was degraded due to fluorescence. The results indicate that imported data recorded at a different NIR wavelength can be successfully used as reference libraries, but key issues must be addressed: the reference data must be of equal or higher resolution than the resolution of the current sensor, the systems require rigorous wavelength calibration, and wavelength-dependent intensity response should be accounted for in the different systems.

Potential of Near-Infrared Fourier Transform Raman Spectroscopy in Food Analysis

1992 ◽  
Vol 46 (10) ◽  
pp. 1503-1507 ◽  
Author(s):  
Y. Ozaki ◽  
R. Cho ◽  
K. Ikegaya ◽  
S. Muraishi ◽  
K. Kawauchi
Keyword(s):  
Raman Spectroscopy ◽  
Fourier Transform ◽  
Fatty Acid ◽  
Raman Spectra ◽  
Food Analysis ◽  
Near Infrared ◽  
Egg White ◽  
Ft Raman Spectroscopy ◽  
Ft Raman

The 1064-nm excited Fourier transform (FT) Raman spectra have been measured in situ for various foods in order to investigate the potential of near-infrared (NIR) FT-Raman spectroscopy in food analysis. It is demonstrated here that NIR FT-Raman spectroscopy is a very powerful technique for (1) detecting selectively the trace components in foodstuffs, (2) estimating the degree of unsaturation of fatty acids included in foods, (3) investigating the structure of food components, and (4) monitoring changes in the quality of foods. Carotenoids included in foods give two intense bands near 1530 and 1160 cm−1 via the pre-resonance Raman effect in the NIR FT-Raman spectra, and therefore, the NIR FT-Raman technique can be employed to detect them nondestructively. Foods consisting largely of lipids such as oils, tallow, and butter show bands near 1658 and 1443 cm−1 due to C=C stretching modes of cis unsaturated fatty acid parts and CH2 scissoring modes of saturated fatty acid parts, respectively. It has been found that there is a linear correlation for various kinds of lipid-containing foods between the iodine value (number) and the intensity ratio of two bands at 1658 and 1443 cm−1 ( I1658/ I1443), indicating that the ratio can be used as a practical indicator for estimating the unsaturation level of a wide range of lipid-containing foods. A comparison of the Raman spectra of raw and boiled egg white shows that the amide I band shifts from 1666 to 1677 cm−1 and the intensity of the amide III band at 1275 cm−1 decreases upon boiling. These observations indicate that most α-helix structure changes into unordered structure in the proteins constituting egg white upon boiling. The NIR FT-Raman spectrum of old-leaf (about one year old) Japanese tea has been compared with that of its new leaf. The intensity ratio of two bands at 1529 and 1446 cm−1 ( I1529/ I1446), assignable to carotenoid and proteins, respectively, is considerably smaller in the former than in the latter, indicating that the ratio is useful for monitoring the changes in the quality of Japanese tea.

Self-Modeling Mixture Analysis Applied to FT-Raman Spectral Data of Hydrogen Peroxide Activation by Nitriles

1997 ◽  
Vol 51 (3) ◽  
pp. 407-415 ◽  
Author(s):  
V. Vacque ◽  
N. Dupuy ◽  
B. Sombret ◽  
J. P. Huvenne ◽  
P. Legrand
Keyword(s):  
Spectral Data ◽  
Chemical Transformations ◽  
Mixture Analysis ◽  
Ft Raman Spectroscopy ◽  
Raman Spectral Data ◽  
Raman Spectral ◽  
Kinetics Of ◽  
Peroxide Activation ◽  
Ft Raman

In the analytical environment, spectral data resulting from analysis of samples often represent mixtures of several components. Extraction of information about pure components of these kinds of mixtures is a major problem, especially when reference spectra are not available or when unstable intermediates are formed. Self-modeling multivariate mixture analysis has been developed for this type of problem. In this paper two examples will be used to show the potential of this technique coupled with FT-Raman spectroscopy to elucidate reaction mechanisms and to follow in situ the kinetics of chemical transformations.

scholarly journals High-resolution, non-scanning FTS for remote sensing

1995 ◽  
Vol 149 ◽  
pp. 338-339
Author(s):  
K. Døhlen ◽  
A. Cañas
Keyword(s):  
Remote Sensing ◽  
Fourier Transform ◽  
High Resolution ◽  
Near Infrared ◽  
Michelson Interferometer ◽  
Resolving Power ◽  
Diode Array ◽  
Sensing Applications ◽  
First Results ◽  
Remote Sensing Applications

We present the first results from a portable spectrometer for the visible and very near infrared based upon the principle of heterodyned holographic Fourier transform spectroscopy (HHS) (Dohi and Suzuki 1971, Dohlen 1994). The instrument uses a Michelson interferometer where one of the mirrors is replaced with a grating. This produces a spatially located, frequency-shifted interferogram which is read out by an all-reflective relay lens and a photo-diode array and processed on a portable PC. A battery pack ensures an autonomy of about 7 hours. Instrumental assets include high optical throughput, variable resolving power, and no moving parts.We have successfully used the instrument in two different remote sensing applications: detection of vegetation reflectance and atmospheric absorption.

Fourier Transform Raman Spectroscopy of Long-Chain Molecules Containing Strongly Absorbing Chromophores

1987 ◽  
Vol 41 (5) ◽  
pp. 721-726 ◽  
Author(s):  
C. G. Zimba ◽  
V. M. Hallmark ◽  
J. D. Swalen ◽  
J. F. Rabolt
Keyword(s):  
Raman Spectroscopy ◽  
Fourier Transform ◽  
Near Infrared ◽  
Visible Region ◽  
Excitation Spectra ◽  
Chain Molecules ◽  
Scattering Geometry ◽  
Fourier Transform Raman Spectroscopy ◽  
Fourier Transform Raman ◽  
Ft Raman

Fourier transform Raman spectroscopy shows considerable promise as a new characterization technique for molecules which contain chromophores which absorb in the visible region, the region where conventional Raman measurements are made. With the use of near-infrared excitation, spectra in the absence of fluorescence and resonance enhancement are obtained. These advantages can be further enhanced if the collection of data using this technique becomes routine, requiring a level of complexity comparable to that of conventional Raman scattering. Toward that end, the implementation of a 90° scattering geometry in our FT-Raman measurements was undertaken, and the results are shown to be at least comparable to those obtained with the use of reflective optics in a 180° geometry. A number of results on both liquids and solids have also been obtained in order to compare FT-Raman with conventional scanning Raman measurements.

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