Attenuated total reflection spectra under conditions of weak absorption: physical nature

Stuchebryukov, S. D.; Rudoy, V. M.

doi:10.1016/s0030-4018(97)00143-0

Cited by 3 publications

(4 citation statements)

References 3 publications

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“…. 18,19,35 On the other hand, Stuchebryukov and Rudoy 12 showed that an ATR spectrum can be considered as the spectrum of the imaginary part of the dielectric constant, ε″(ω). Since the complex dielectric constant, ε̂= ε′ + iε″, and refractive index, n= n + ik, are related by the fundamental equation ε̂= n̂2, then ε′(ω) = n 2 (ω) − k 2 (ω) and ε″(ω) = 2n(ω)k(ω).…”

Section: Methodsmentioning

confidence: 99%

“…Spectral resolution was 2 cm –1 . Optical effects can result in differences between transmission and reflection measurements. − ATR is a technique appropriate for quantitative IR spectroscopy since it allows for better control of sample size and thickness. , Moreover, ATR Fourier transform IR spectrum can be used to obtain optical constants − ,,, (i.e., frequency-dependent refractive index and extinction coefficient), as shown by Buffeteau et al for different ionic liquids. Figure illustrates differences in relative intensities and vibrational frequencies that can be found between transmission and ATR measurements of IR spectra of a given ionic liquid, [C 4 C 1 im][CF 3 SO 3 ].…”

Section: Methodsmentioning

confidence: 99%

“…In fact, Figure C compares transmission and ATR spectra of [C 4 C 1 im][CH 3 COO], the latter exhibiting lower intensity of water bands in comparison with the former, being the spectra normalized by an ionic liquid band. The strong variation of the real part of the refractive index, n (ω), within the range of wavenumbers ω of an IR absorption (i.e., the so-called anomalous dispersion as illustrated in Figure D for liquid water (green line), might imply significant differences between ATR and transmission measurements of IR spectra. − The molar absorption coefficient E m , given by E m = A 10 / Cd , where d is the path length, C is the molar concentration, and A 10 is the decadic absorbance following the Beer’s Law, is related to the imaginary part of the refractive index, . ,, On the other hand, Stuchebryukov and Rudoy showed that an ATR spectrum can be considered as the spectrum of the imaginary part of the dielectric constant, ε″(ω). Since the complex dielectric constant, ε̂ = ε′ + iε ″, and refractive index, n̂ = n + ik , are related by the fundamental equation ε̂ = n̂ 2 , then ε′(ω) = n 2 (ω) – k 2 (ω) and ε″(ω) = 2 n (ω) k (ω).…”

Section: Methodsmentioning

confidence: 99%

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Vibrational Spectroscopy of Ionic Liquids

2017

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Vibrational spectroscopy has continued use as a powerful tool to characterize ionic liquids since the literature on room temperature molten salts experienced the rapid increase in number of publications in the 1990's. In the past years, infrared (IR) and Raman spectroscopies have provided insights on ionic interactions and the resulting liquid structure in ionic liquids. A large body of information is now available concerning vibrational spectra of ionic liquids made of many different combinations of anions and cations, but reviews on this literature are scarce. This review is an attempt at filling this gap. Some basic care needed while recording IR or Raman spectra of ionic liquids is explained. We have reviewed the conceptual basis of theoretical frameworks which have been used to interpret vibrational spectra of ionic liquids, helping the reader to distinguish the scope of application of different methods of calculation. Vibrational frequencies observed in IR and Raman spectra of ionic liquids based on different anions and cations are discussed and eventual disagreements between different sources are critically reviewed. The aim is that the reader can use this information while assigning vibrational spectra of an ionic liquid containing another particular combination of anions and cations. Different applications of IR and Raman spectroscopies are given for both pure ionic liquids and solutions. Further issues addressed in this review are the intermolecular vibrations that are more directly probed by the low-frequency range of IR and Raman spectra and the applications of vibrational spectroscopy in studying phase transitions of ionic liquids.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Vibrational Spectroscopy of Ionic Liquids

2017

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“…The corresponding range was also removed from DR spectra to allow a valid comparison. The differences in the frequencies in Table 1 are due to the effect of anomalous dispersion on the ATR spectra [32] and/or the effect of specular reflection in the DR spectra [24].…”

Section: Resultsmentioning

confidence: 99%

A comparative study of mid-infrared diffuse reflection (DR) and attenuated total reflection (ATR) spectroscopy for the detection of fungal infection on RWA2-corn

Kos

Krska

Lohninger

et al. 2004

Analytical and Bioanalytical Chemistry

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An investigation into the rapid detection of mycotoxin-producing fungi on corn by two mid-infrared spectroscopic techniques was undertaken. Corn samples from a single genotype (RWA2, blanks, and contaminated with Fusarium graminearum) were ground, sieved and, after appropriate sample preparation, subjected to mid-infrared spectroscopy using two different accessories (diffuse reflection and attenuated total reflection). The measured spectra were evaluated with principal component analysis (PCA) and the blank and contaminated samples were classified by cluster analysis. Reference data for fungal metabolites were obtained with conventional methods. After extraction and clean-up, each sample was analyzed for the toxin deoxynivalenol (DON) by gas chromatography with electron capture detection (GC-ECD) and ergosterol (a parameter for the total fungal biomass) by high-performance liquid chromatography with diode array detection (HPLC-DAD). The concentration ranges for contaminated samples were 880-3600 microg/kg for ergosterol and 300-2600 microg/kg for DON. Classification efficiency was 100% for ATR spectra. DR spectra did not show as obvious a clustering of contaminated and blank samples. Results and trends were also observed in single spectra plots. Quantification using a PLS1 regression algorithm showed good correlation with DON reference data, but a rather high standard error of prediction (SEP) with 600 microg/kg (DR) and 490 microg/kg (ATR), respectively, for ergosterol. Comparing measurement procedures and results showed advantages for the ATR technique, mainly owing to its ease of use and the easier interpretation of results that were better with respect to classification and quantification.

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Attenuated total refection spectroscopy under conditions weak absorption: New method for determination of integrated intensities

Stuchebryukov

2010

Prot Met Phys Chem Surf

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Attenuated total reflection spectra under conditions of weak absorption: physical nature

Cited by 3 publications

References 3 publications

Vibrational Spectroscopy of Ionic Liquids

Vibrational Spectroscopy of Ionic Liquids

A comparative study of mid-infrared diffuse reflection (DR) and attenuated total reflection (ATR) spectroscopy for the detection of fungal infection on RWA2-corn

Attenuated total refection spectroscopy under conditions weak absorption: New method for determination of integrated intensities

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