ATR FTIR spectroscopy

An IRE consists of an IR-transparent material with a high refractive index, for example zinc selenide (ZnSe), a mixmre of thallium bromide and iodide (KRS-5), cadmium telluride (CdTe) or germanium (Ge) (Hind et al., 2001). Its shape is determined by functional aspects (1) the IR beam must enter and leave it with an angle providing total reflection at sample side, (2) the number of total reflections has to be defined and (3) the design is determined by the respective measuring accessory. 

ATR spectra are quite similar to conventional absorbance spectra recorded by transmission through a sample. However, there is a cmcial difference because of the 

Here n and ni are the refractive indices of the IRE and ambient/sample, X the used wavelength and 6 is the AOI of the IR radiation relative to a perpendicular of the surface. 

It should be noted that is not the depth that is sampled in the ATR experiment as E is not zero at d. It only gives an impression about the scale to what depth information can be gained approximately and how it will change over the spectral range. The real depth of information is related to the penetration depth but also relies very much on the sensitivity and SNR of IR equipment used. The sample thickness of a material recorded in transmission at normal incidence giving the same absorbance as in the ATR spectrum is called effective thickness 

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Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy. Attenuated total redectance (atr) ftir spectroscopy is based on the principle of total internal redection (40). Methods based on internal redection in the uv and visible regions of the spectmm are also common in addition to those in the ir region. The implementation of internal redection in the ir region of the spectmm provides a means of obtaining ir spectra of surfaces or interfaces, thus providing moleculady-specific vibrational information. 

Dunuwila, D. and Berglund, K.A. 1997. ATR FTIR spectroscopy for in situ measurement of supersaturation. Journal of Crystal Growth, 179, 185-193. 

Chen Y-X, Ye S, Heinen M, Jusys Z, Osawa M, Behm RJ. 2006c. Application of in-situ ATR-FTIR spectroscopy for the understanding of complex reaction mechanism and kinetics Formic acid oxidation on a Pt electrode at elevated temperatures. J Phys Chem B 110 9534-9544. 

Kazarian et al. [281-283] have used various spectroscopic techniques (including FUR, time-resolved ATR-FHR, Raman, UV/VIS and fluorescence spectroscopy) to characterise polymers processed with scC02. FTIR and ATR-FTIR spectroscopy have played an important role in developing the understanding and in situ monitoring of many SCF processes, such as drying, extraction and impregnation of polymeric materials. 

In order to first ascertain whether the non-melt area was a contaminant, ATR-FTIR spectroscopy was used to analyze and compare the two areas. It was found that both areas were polycaprolactone, and that the spectra match between the two was greater than 98%, indicating that they were the same base resin, thus ruling out a contaminant. These spectra are shown in Figure 9. 

Si element ATR-FTIR spectroscopy was used to analyze this residue, and its spectrum, along with the closest library matches, are shown in Figure 41. The absorbance of this residue is low as a consequence of the thin layer present on the plate. This makes matching the sample spectrum with a reference spectrum somewhat difficult. The closest matches extracted from the library interrogated are to ester-based plasticizer materials, which is consistent with a phthalate-plasticized PVC. A more specific identification could have been made with further testing such as subjecting the residue to GC-MS analysis, but the information suggested by the ATR-FTIR analysis was, in this case sufficient. 

Finally, both samples were analyzed using ATR-FTIR spectroscopy. The Si ATR crystal was brought into contact with the sample, and spectra recorded. Figure 51 compares the spectra. Based on the excellent match factor between the spectra of the two samples (99.8%) and visual comparison of these two spectra,... 

In another catheter failure study, two samples of multi-layer catheters were tested. One catheter was breaking while the other was known to be a "good" sample. The catheters were freeze-fractured in order to obtain a cross-section view for SEM analysis, which was used to determine the construction of the catheter layers. ATR-FTIR spectroscopy was undertaken to identify the polymers used in the multi-layer catheter samples. 

ATR-FTIR spectroscopy was conducted at four locations on sample 1 and sample 2 as indicated on Figures 53 and 55, respectively... 

Regan F., Meaney M., Vos J. G., MacCraith B.D., Walsh J.E., Determination of pesticides in water using ATR-FTIR spectroscopy on PVC/chloroparaffin coatings, Anal. Chim. Acta, 1996 334 85-92. 

WOJCIECHOWSKI C, DUPUY N, TA C D, HUVENNE J P and LEGRAND P (1998), Quantitative analysis of water-soluble vitamins by ATR-FTIR spectroscopy , Food Chem, 63, 133 10. woodward j r, brunsman A, gibson t D and Parker s (1998), Practical... 

Jabbari, E., Wisniewski, N., and Peppas, N.A., Evidence of mucoadhesion by chain interpenetration at a poly(acrylic acid)/mucin interface using ATR-FTIR spectroscopy, J. Control. Rel., 26 99-108 (1993). 

Another similar study of crystallization was performed where on-line ATR-FTIR spectroscopy was used to provide concentration information, however on-line diffuse reflectance Fourier-transform infrared... 

Recently, on-line FBRM, ATR-FTIR spectroscopy, Raman spectroscopy and PLS were used to moifitor a complex crystallization system a racemic free base of a given componnd and a chiral acid. The anthors first demonstrate that the diastereomeric composition can be estimated nsing Raman spectral data, slnrry density and temperature using a PLS model. Consequently the issne of on-line slurry density prediction, which is not readily available, arises. An additional PLS model was constructed that used the ATR-FTIR spectral data to infer slurry density. Slurry density as predicted in real-time via ATR-FTIR spectroscopy was fed into the aforementioned Raman, slurry density and temperatnre PLS model to yield a more accnrate estimate of the fractional solid composition of the two diastereomers. ... 

M. Fujiwara, P.S. Chow, D.L. Ma and R.D. Braatz, Paracetamol crystallization using laser backscatteiing and ATR-FTIR spectroscopy metastability, agglomeration, and control, Cryst. Growth Des., 2(5), 363-370 (2002). 

Powdering, or grinding, of samples is a simple preparation method required in a number of spectrometric and spectroscopic techniques, such as x-ray diffraction (XRD), nuclear magnetic resonance (NMR), differential thermal analysis (DTA), thermogravimetric analysis (TG), or ATR-FTIR spectroscopy. Control of the particle size during grinding must be taken into account in attempting to obtain reliable results. 

One other in situ technique can be used to determine fractional acidity in atmospheric aerosols by means of Fourier transform infrared (FTIR) spectroscopy (46). Originally, impactor samples were collected and were pressed into a KBr matrix, and then the IR spectrum was taken by attenuated total reflectance (ATR) FTIR spectroscopy to determine relative acidity, based on differences in absorption bands for sulfate and bisulfate species. Aerosols with [H+]/[S042 ] ratios greater than 1 could also be qualitatively identified. More recent innovations in the FTIR technique (47, 48) have made possible... 

Subramanian, A., Harper, J. W., and Rodriguez-Saona, L. E. (2009b). Rapid prediction of composition and flavor quality of Cheddar cheese using ATR-FTIR spectroscopy. I. Food Sci. 74, C292-C297. 

To shed light on the mechanism of formation of silsesquioxane a7b3, to identify the species formed during the process, and to try to explain the high selectivity towards structure a7b3 of the optimised synthetic method described above (64% yield in 18 h), the synthesis of cyclopentyl silsesquioxane a7b3 was monitored by electrospray ionisation mass spectrometry (ESI MS) [50-52] and in situ attenuated total reflection Fourier-transform infrared (ATR FTIR) spectroscopy [53, 54]. Spectroscopic data from the latter were analysed using chemometric methods to identify the pure component spectra and relative concentration profiles. 

Muller M, Kessler B, Adler H-J et al (2004) Reversible switching of protein uptake and release at polyelectrolyte multilayers detected by ATR-FTIR spectroscopy. Macromol Symp 210 157-164... 

M. Muller (2002) ATR-FTIR Spectroscopy at Polyelectrolyte Multilayer Systems. In Tri-pathy SK, Kumar J, Nalwa HS (eds) Handbook of Polyelectrolytes and Their Applications. American Scientific (ASP), pp 293-312... 

A closed-system microwave plasma reactor was used to react imidazole molecules to PVC surfaces. Newly created surfaces were analysed using ATR FTIR spectroscopy. Surface reactions on PVC were heavily dependent on a prior thermal history of the PVC substrate. A mechanism for the PVC-imidazole reactions was also presented. The PVC was useful as an implant for biomedical applications. 10 refs. 

Figure 21 Correlation between the concentrations of CP in the SC, following a 15-minute exposure to an aqueous solution of the chemical, as measured by ATR-FTIR spectroscopy and by liquid scintillation counting (LSC). The accumulated data from four different subjects (78 measurements) are shown. The line of linear regression drawn through the data is y = 1,07x + 0.08 (r = 0.796, p < 0.0001). The values of the slope and intercept are not significantly different from 1 and 0 (p < 0.05), respectively. (From Ref. 175.)...

Farinas, K. C. et al. Characterisation of solute diffusion in a polymer using ATR-FTIR spectroscopy and bulk transport techniques. Macromolecules 27(18) 5220-5222, 1994. 

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