Near- versus Mid-Infrared Spectroscopy: Relationships between Spectral Changes Induced by Water and Relative Information Content of the Two Spectral Regions in Regard to High-Moisture Samples

1995 ◽  
Vol 49 (3) ◽  
pp. 295-303 ◽  
Author(s):  
James B. Reeves
Keyword(s):  
Infrared Spectra ◽  
Near Infrared ◽  
High Moisture ◽  
Mid Infrared ◽  
Spectral Changes ◽  
Near Infrared Spectra ◽  
Infrared Spectral ◽  
Water Ph ◽  
Relative Information Content ◽  
Relationship Of

The objectives of this work were to examine similarities and differences in the near-infrared and mid-infrared spectral regions when one is working with high-moisture materials and to study spectral changes in these regions as a method to identify the relationship of spectral information in the near-IR to fundamental absorptions in the mid-IR. Near- and mid-infrared spectra were taken with a Digilab FTS-65 Fourier transform spectrometer. Liquids were examined by transmission and solids by reflectance. Results with solutions showed that less spectral distortion arises when one is subtracting water from mid- rather than from near-infrared spectra. It was also easier to produce high-quality spectra in the mid-infrared by using attenuated total reflectance than by using transmission in the near-infrared. While mid-infrared spectra showed changes (induced by water, pH, physical state, and ionic strength) similar to those found in the near-infrared, there appeared to be more information available in the mid-infrared, even in the presence of water.

Mid and near Infrared Study of Carbohydrates by Canonical Correlation Analysis

1993 ◽  
Vol 1 (2) ◽  
pp. 99-108 ◽  
Author(s):  
P. Robert ◽  
M.F. Devaux ◽  
A. Qannari ◽  
M. Safar
Keyword(s):  
Correlation Analysis ◽  
Infrared Spectra ◽  
Canonical Correlation ◽  
Near Infrared ◽  
Sugar Content ◽  
Infrared Region ◽  
Total Sugar ◽  
Mid Infrared ◽  
Total Sugar Content ◽  
Near Infrared Spectra

Multivariate data treatments were applied to mid and near infrared spectra of glucose, fructose and sucrose solutions in order to specify near infrared frequencies that characterise each carbohydrate. As a first step, the mid and near infrared regions were separately studied by performing Principal Component Analyses. While glucose, fructose and sucrose could be clearly identified on the similarity maps derived from the mid infrared spectra, only the total sugar content of the solutions was observed when using the near infrared region. Characteristic wavelengths of the total sugar content were found at 2118, 2270 and 2324 nm. In a second step, the mid and near infrared regions were jointly studied by a Canonical Correlation Analysis. As the assignments of frequencies are generally well known in the mid infrared region, it should be useful to study the relationships between the two infrared regions. Thus, the canonical patterns obtained from the near infrared spectra revealed wavelengths that characterised each carbohydrate. The OH and CH combination bands were observed at: 2088 and 2332 nm for glucose, 2134 and 2252 nm for fructose, 2058 and 2278 nm for sucrose. Although a precise assignment of the near infrared bands to chemical groups within the molecules was not possible, the present work showed that near infrared spectra of carbohydrates presented specific features.

Determination of Protein in Ground Wheat Samples by Mid-Infrared Diffuse Reflectance Spectroscopy

1997 ◽  
Vol 51 (8) ◽  
pp. 1200-1204 ◽  
Author(s):  
James B. Reeves ◽  
Stephen R. Delwiche
Keyword(s):  
Protein Content ◽  
Infrared Spectra ◽  
Diffuse Reflectance ◽  
Near Infrared ◽  
Diffuse Reflectance Spectroscopy ◽  
Reflectance Spectroscopy ◽  
Mid Infrared ◽  
Near Infrared Spectra ◽  
Hard Red Winter Wheat ◽  
Ground Wheat

The objective of this study was to determine whether mid-infrared diffuse reflectance spectroscopy could be used in the same manner as near-infrared diffuse reflectance spectroscopy to quantitatively determine the protein content of ground wheat samples. One hundred and thirty hard red winter wheat samples were assayed for protein by combustion and scanned in the near- and mid-infrared. Samples (UDY ground) were scanned neat in the near-infrared from 1100 nm (9091 cm−1) to 2498 nm (4003 cm−1) on a scanning monochromator and in the mid-infrared from 4000 cm−1 (2500 nm) to 400 cm−1 (25,000 nm) on a Fourier transform spectrometer at 4-and 16-cm−1 resolutions. Protein content varied from a low of 8.98% to a high of 18.70% (average of 12.86% with a standard deviation of 1.66%). Calibrations developed with the use of partial least-squares gave an R2 and bias-corrected standard error of performance of 0.999 and 0.054 for the near-infrared and 0.997 and 0.085 for the mid-infrared (4 cm−1 resolution). Calibration results based on mid-infrared spectra, while not as good as those for near-infrared spectra, were nevertheless quite good. These results demonstrate that it is possible to develop satisfactory calibrations for protein in ground wheat with the use of mid-infrared spectra without the need for sample dilution with KBr.

Near Infrared Spectroscopic Examination of Charred Pine Wood, Bark, Cellulose and Lignin: Implications for the Quantitative Determination of Charcoal in Soils

2007 ◽  
Vol 15 (5) ◽  
pp. 307-315 ◽  
Author(s):  
James B. Reeves ◽  
Gregory W. McCarty ◽  
David W. Rutherford ◽  
Robert L. Wershaw
Keyword(s):  
Carboxylic Acids ◽  
Infrared Spectra ◽  
Near Infrared ◽  
Direct Determination ◽  
Pine Wood ◽  
Oh Groups ◽  
Spectral Changes ◽  
Near Infrared Spectra ◽  
Material Temperature

The objective of this research was to investigate the effect of charring on near infrared spectra of materials likely to be present in forest fires in order to determine the feasibility of determining charred carbon in soils. Four materials (cellulose, lignin, pine bark and pine wood) and char from these materials created by charring for various durations (1 to 168 h) and at various temperatures (200 to 450°C) were studied. Near infrared spectra and measures of acidity (total acids, carboxylic acids, lactones and phenols as determined by titration) were available for 56 different samples (Not all samples charred at all temperatures/durations). Results showed spectral changes that varied with the material, temperature and duration of charring. Examination of spectra and correlation plots indicated that changes in the constituents of the materials in question, such as loss of OH groups in carbohydrates, rather than direct determination of typical products produced by charring, such as carboxylic acids, lactones and phenols, were the basis for the spectral changes. Finally, while the spectral changes resulting from charring appeared to be relatively unique to each material, PLS calibrations for total acids, carboxylic acids, lactones and phenols were successfully created (with R2 of 0.991, 0.943, 0.931 and 0.944, respectively) indicating that there is a sufficient commonality in the changes to develop calibrations without the need for unique calibrations for each specific set of charring conditions (i.e. material, temperature and time of heating).

Spectral Effects of Water in the 10,000 to 8000 cm−1 (1000 to 1250 nm) near Infrared Spectral Region. And, Can They Explain Previously Seen Effects of Water in the Spectral Region from 14,000 to 11,500 cm−1 (714 to 870 nm)?

1995 ◽  
Vol 3 (3) ◽  
pp. 143-153 ◽  
Author(s):  
James B. Reeves
Keyword(s):  
Spectral Region ◽  
Diffuse Reflectance ◽  
Near Infrared ◽  
Detailed Examination ◽  
Fourier Transform Spectrometer ◽  
High Moisture ◽  
Mid Infrared ◽  
Infrared Spectral ◽  
And Shifts ◽  
Optic Systems

The spectral region from 10,000 to 8000 cm−1 (1000 to 1250 nm) is often used for high moisture samples and fibre optic systems. The first objective of this work was to determine the effects of water on the spectra of various types of materials in this spectral region. The second objective was to determine the origin/nature of spectral effects/artifacts seen in the spectral region from 14,000 to 11,500 cm−1 (714 to 870 nm) when water was added to gums and proteins (increases in peak intensities and shifts in position due to the presence of water). Spectra were obtained by diffuse reflectance and transmission using a Fourier transform spectrometer. The results showed that the effects seen in the mid-infrared and near infrared from 8000 to 4000 cm−1 (1250 to 2500 nm) were also common in this part of the near infrared (i.e. peak shifts, loss of spectral features etc). Thus, the spectra of crystalline glucose and sucrose, while distinctively different as crystalline solids, were very similar when in solution and changes in the spectra of materials, such as acetone, pyridine and ethanol, were very similar in nature to those previously found in the near infrared from 8000 to 4000 cm−1 (1250 to 2500 nm). Finally, detailed examination of spectra in the region from 10,000 to 8000 or 6000 cm−1 (1000 to 1250 or 1667 nm) did not show any spectral effects similar to those seen in gums and proteins in the 14,000 to 11,500 cm−1 (714 to 870 nm) region. Thus, the nature of these effects is still unknown.

scholarly journals Potential Drivers of Mid-Infrared Variability in Young Stars: Testing Physical Models with Multiepoch Near-Infrared Spectra of YSOs in ρ Oph

2012 ◽  
Vol 124 (921) ◽  
pp. 1137-1158 ◽  
Author(s):  
Christopher M. Faesi ◽  
Kevin R. Covey ◽  
Robert Gutermuth ◽  
Maria Morales–Calderón ◽  
John Stauffer ◽  
...  
Keyword(s):  
Infrared Spectra ◽  
Near Infrared ◽  
Young Stars ◽  
Physical Models ◽  
Mid Infrared ◽  
Near Infrared Spectra

Efforts to Quantify Changes in Near-Infrared Spectra Caused by the Influence of Water, pH, Ionic Strength, and Differences in Physical State

1995 ◽  
Vol 49 (2) ◽  
pp. 181-187 ◽  
Author(s):  
James B. Reeves
Keyword(s):  
Amino Acids ◽  
Ionic Strength ◽  
Infrared Spectra ◽  
Physical State ◽  
Near Infrared ◽  
Near Ir ◽  
Near Infrared Spectra ◽  
Influence Of Water ◽  
Water Ph ◽  
Crystalline Sugars

The application of near-infrared spectroscopy to high-moisture samples has shown that the accuracy does not match that found for dried materials. The objective of this work was to attempt to quantify the effects of water, pH, ionic strength, and differences in physical state on near-infrared spectra with the use of model compounds. Spectra were compared by regression analysis of second derivatives after spectral subtraction of water. Spectra from 4900 to 4100 cm−1 at a resolution of 4 cm−1 were examined. Regression results showed spectra to be more similar among amorphous sugars and among dissolved sugars than among crystalline sugars. Also, spectra of amorphous sugars were statistically more similar to spectra of dissolved sugars than to spectra of crystalline sugars. While the spectra of one dissolved or amorphous sugar were statistically similar, this was not true for amino acids. Spectra of amorphous amino acids were similar to those of crystalline forms and neither were similar to those of dissolved forms. Spectrally, polymeric carbohydrates appeared very similar to one another when dry and behaved like amino acids when wet. Finally, efforts to directly relate these findings to near-IR spectroscopy calibration problems will require further research.

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