Analysis of weak surface absorption bands in the near-infrared spectra of Mars obtained by Phobos-2

The temperature sensitivity of underlying water absorption bands can lead to baseline artifacts or apparent spectral band shifts in near infrared spectra and can negatively impact multivariate calibration models used in quantitative analyses. To address this issue, efforts can be made to suppress the temperature-induced spectral variation or knowledge of the temperature can be used to adjust the calibration. To facilitate the latter approach, we explored the ability to estimate the aqueous temperature of the sample directly from the combination region of the near infrared spectrum. This temperature modeling strategy addresses applications in which it is difficult to obtain an accurate sample temperature with a conventional measurement probe. Temperature models were developed by use of partial least-squares regression combined with the discrete wavelet transform. Models were constructed from the 5000 to 4000 cm−1 region of near infrared spectra for pH 7.4 buffer solutions over the temperature range of 20.0–40.5℃. The long-term predictive ability of the models was assessed by use of 13 sets of prediction spectra collected over the course of 13 months, yielding values of the root mean square error of prediction ranging from 0.19 to 0.36℃. In addition, laboratory-prepared solutions of glucose, mixture solutions of glucose, lactate, urea in buffer, and bovine plasma were used to assess the predictive ability of the temperature models in increasingly complex matrixes. The effects of pH and buffer molarity were also studied. While increasing the complexity of the spectral background resulted in increases in root mean square error of prediction (0.33–1.01℃), retuning the models to incorporate the modified spectral backgrounds lowered the resulting root mean square error of prediction values to the range of 0.3℃. This work demonstrates the practical utility of spectral-based temperature measurements that employ the absorbance of the water baseline rather than the peak absorbance.

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Near infrared spectra of some cobalt(II) compounds

Australian Journal of Chemistry ◽

10.1071/ch9681775 ◽

1968 ◽

Vol 21 (7) ◽

pp. 1775

Author(s):

DP Graddon ◽

GM Mockler

Keyword(s):

Absorption Band ◽

Absorption Spectra ◽

Metal Atom ◽

Infrared Spectra ◽

Near Infrared ◽

Infrared Region ◽

Absorption Bands ◽

Heterocyclic Base ◽

Near Infrared Spectra ◽

Near Infrared Region

Absorption spectra of compounds CoX2B2 and CoX2B4 (X = Cl, Br, I, or NCS; B = a heterocyclic base) have been obtained by reflectance and in solution in the near infrared region between 1000 and 2000 mμ. The spectra are characteristic of the stereochemistry of the metal atom: octahedral compounds have a single absorption band near 1100 mμ, e < 10; tetrahedral compounds have three overlapping absorption bands near 1100,1400, and 1700 mp, 30 < < 150. Comparisons are made with previously observed spectra of octahedral and tetrahedral species of the types CoL2+6 and CoX2-4.

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Assessment of Partial Least-Squares Calibration and Wavelength Selection for Complex Near-Infrared Spectra

Applied Spectroscopy ◽

10.1366/0003702981944427 ◽

1998 ◽

Vol 52 (6) ◽

pp. 878-884 ◽

Cited By ~ 26

Author(s):

Michael J. McShane ◽

Gerard L. Coté ◽

Clifford H. Spiegelman

Keyword(s):

Least Squares ◽

Partial Least Squares ◽

Infrared Spectra ◽

Near Infrared ◽

Wavelength Selection ◽

Absorption Bands ◽

Full Spectrum ◽

Single Spectrum ◽

Near Infrared Spectra ◽

Selection For

Complex near-infrared (near-IR) spectra of aqueous solutions containing five independently varying absorbing species were collected to assess the ability of partial least-squares (PLS) regression and wavelength selection for calibration and prediction of these species in the presence of each other. It was confirmed that PLS calibration models can successfully predict chemical concentrations of all five chemicals from a single spectrum. It was observed from the PLS spectral loadings that spectral regions containing absorption bands of a single analyte alone were not sufficient for the model to adequately predict the concentration of the analyte because of the high degree of overlap between glucose, lactate, ammonia, glutamate, and glutamine. Three wavelength selection algorithms were applied to the spectra to identify regions containing necessary information, and in each case it was found that nearly the entire spectral range was needed for each determination. The results suggest that wavelength selection does result in a reduction of data points from the full spectrum, but the decrease seen with these near-infrared spectra was less than typically seen in mid-IR or Raman spectra, where peaks are narrower and well separated. As a result of this need for more wavelengths, the engineering of a dedicated system to measure these analytes in complex media such as blood or tissue culture broths by using this near-infrared region (2.0–2.5 μm) is further complicated.

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"Transitions vibrationnelles simultanées" d'un donneur et d'un accepteur de proton

Canadian Journal of Chemistry ◽

10.1139/v73-307 ◽

1973 ◽

Vol 51 (12) ◽

pp. 2059-2070 ◽

Cited By ~ 11

Author(s):

André Burneau ◽

Jacques Corset

Keyword(s):

Hydrogen Bond ◽

Infrared Spectra ◽

Near Infrared ◽

Proton Donor ◽

Strong Hydrogen Bond ◽

Intensity Increase ◽

Absorption Bands ◽

Near Infrared Spectra ◽

Weak Hydrogen Bonds ◽

Proton Donors

Absorptions simultaneously involving the vibrations of two molecules are brought out of the near infrared spectra of mixtures containing a proton donor RXH and an acceptor R′AB. The donors under study are: chloroform, water, pentachlorophenol, and methanol, and the acceptors: acetonitrile, acetone, dimethylsulfoxide, and pyridine; for comparison, carbon disulfide and hexachloracetone are also used as solvents. Not only the combinations vXH + vAB and vXH + v3(CS2) are observed, but also vXH + vR′, at about 6500 cm−1, if R′ contains CH bonds; these absorptions at 6500 cm−1 do not exist when fully deuterated bases R′AB are used. A correlation between the intensity increase, through hydrogen bonding, of the vXH bands and that of the simultaneous transitions is suggested by the results. In the assignment of the near infrared spectra of proton donors, it is important to take into account the simultaneous transitions because their intensity is sometimes greater than that of the overtones 2vXH. It is likely that these conclusions, founded on the study of relatively weak hydrogen bonds, may be extended to stronger interactions; but the width of the absorption bands in the case of strong hydrogen bond makes the observation of the simultaneous transitions difficult.

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Evaluation of near-infrared spectra for detecting ammonium minerals at Shoshone Geyser Basin, Yellowstone National Park, Wyoming

Open-File Report ◽

10.3133/ofr93293 ◽

1993 ◽

Author(s):

M.D. Krohn

Keyword(s):

Infrared Spectra ◽

Yellowstone National Park ◽

National Park ◽

Near Infrared ◽

Near Infrared Spectra

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Rapid Determining Contents of the Rhubarb Anthraquinones Compounds by Support Vector Machines Modeling based on Near Infrared Spectra

Current Analytical Chemistry ◽

10.2174/1573411016666200317111412 ◽

2020 ◽

Vol 16 ◽

Author(s):

Linqi Liu ◽

JInhua Luo ◽

Chenxi Zhao ◽

Bingxue Zhang ◽

Wei Fan ◽

...

Keyword(s):

Infrared Spectra ◽

Near Infrared ◽

Mean Squared Error ◽

Rapid Determination ◽

Partial Least Square ◽

Least Square ◽

Support Vector ◽

Near Infrared Spectra ◽

Aloe Emodin ◽

Relative Differences

BACKGROUND: Measuring medicinal compounds to evaluate their quality and efficacy has been recognized as a useful approach in treatment. Rhubarb anthraquinones compounds (mainly including aloe-emodin, rhein, emodin, chrysophanol and physcion) are its main effective components as purgating drug. In the current Chinese Pharmacopoeia, the total anthraquinones content is designated as its quantitative quality and control index while the content of each compound has not been specified. METHODS: On the basis of forty rhubarb samples, the correlation models between the near infrared spectra and UPLC analysis data were constructed using support vector machine (SVM) and partial least square (PLS) methods according to Kennard and Stone algorithm for dividing the calibration/prediction datasets. Good models mean they have high correlation coefficients (R2) and low root mean squared error of prediction (RMSEP) values. RESULTS: The models constructed by SVM have much better performance than those by PLS methods. The SVM models have high R2 of 0.8951, 0.9738, 0.9849, 0.9779, 0.9411 and 0.9862 that correspond to aloe-emodin, rhein, emodin, chrysophanol, physcion and total anthraquinones contents, respectively. The corresponding RMSEPs are 0.3592, 0.4182, 0.4508, 0.7121, 0.8365 and 1.7910, respectively. 75% of the predicted results have relative differences being lower than 10%. As for rhein and total anthraquinones, all of the predicted results have relative differences being lower than 10%. CONCLUSION: The nonlinear models constructed by SVM showed good performances with predicted values close to the experimental values. This can perform the rapid determination of the main medicinal ingredients in rhubarb medicinal materials.

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