Internal reflection method

The in-sifu FTIR approach can be divided into the transmittance, external reflectance and internal reflectance methods. 

Solid state spectra can be measured by the Attenuated Total Reflectance or Multiple Internal Reflection methods as well as by simple transmission techniques (222). Brooker (223) has reported the discovery of the translational vibrations of NaN02, NaNOs, and CaCOs (calcite). The orientation of the bonds in (U02)(N0s)2. 6 H2O has been ascertained from the spectra obtained in this manner (223). 

Internal reflectance methods are a common sampling method in infrared spectrophotometry. The following table provides guidance in the selection of elements for reflectance methods.1... 

IR spectroscopy is a common analytical technique in the textile industry. IR is capable of identifying fibers and their additives, as well as showing quantitative blend ratios and additive contents. The ATR (attenuated total reflection) technique, especially in its multiple form, MIR (multiple internal reflection) is of special importance in this field. The sample preparation is simple and fast the cut out swatches with appropriate surface areas are placed against each side of the MIR crystal, ensuring sufficient and uniform contact across the crystal surface. The internal reflection methods are non-destructive, so that the sample may be saved for other types of analysis, they are, further, methods of surface analysis. This is advantageous in all cases where the finish resides primarily on the fiber surface. In this case, a very strong spectrum of the finish is obtained, with minimal interference from the base fiber (Hannah et al., 1975). 

Modem IR instmments often have reflectance of other sampling capabilities for obtaining IR spectra that eliminate the necessity of salt plate cells and simplify sample handling. The most useful is an internal reflectance method called attenuated total reflectance (ATR). The sample is pressed on a diamond substrate and the infrared radiation penetrates the sample, being reflected internally, and then exits for detection. 

In the internal reflection method a light ray is incident from the interior side of an electrode to the interface. Optically transparent electrodes (OTE), such as tin oxide, metal film electrodes in the visible region, are used to obtain absorption spectra of adsorbed species by multiple reflection (Hansen, 1973 Heinemanetal., 1984 Kuwanaand Winograd, 1974 Mark and Randall, 1970). 

Infrared spectral traces obtained by the internal reflection method applied through test plates exposed for only a few moments in the human mouth, demonstrate the presence of rapidly adsorbed proteinaceous matter. Thus, the reality of the "skin" on one s teeth, or on any other object immersed even momentarily in this rich biological environment, can be documented. It is made of the... 

Reflectance techniques may be used for samples that are difficult to analyze by the conventional transmittance method. In all, reflectance techniques can be divided into two categories internal reflection and external reflection. In internal reflection method, interaction of the electromagnetic radiation on the interface between the sample and a meditnn with a higher refraction index is studied, while external reflectance techniques arise from the radiation reflected from the sample surface. External reflection covers two different types of reflection specular (regular) reflection and diffuse reflection. The former usually associated with reflection from smooth, polished surfaces Hke mirror, and the latter associated with the reflection from rough surfaces. 

ON THE CHOICE OF THE OPTIMUM CONDITIONS FOR THE PRODUCTION OF SPECTRA BY THE FRUSTRATED TOTAL INTERNAL REFLECTION METHOD. 

ON THE CHOICE OF THE OPTIMUM CONDITIONS FOR THE PRODUCTION OF SPECTRA BY THE FRUSTRATED TOTAL INTERNAL REFLECTION METHOD. //ENGLISH TRANSLATION OF OPTIKA I SPEKTROSKOPIYA 19/4/ 623-7,1965.//... 

Measurement of the surface tilt angle induced by the electric field above the threshold for the Prederiks transition (attenuated total internal reflection method)... 

Latexes of synthetic resins are identified by ir spectrometry. Selective extraction with organic solvents is used to obtain purified fractions of the polymers for spectrometric identification. Polymeric films can be identified by the multiple internal reflectance ir technique, if the film is smooth enough to permit intimate contact with the reflectance plate. TAPPI and ASTM procedures have not been written for these instmmental methods, because the interpretation of spectra is not amenable to standardization. 

A method for quantification of the CL, the so-called MAS corrections, in analogy with the ZAP correction method for X rays (see the article on EPMA), has been proposed to account for the effects of the excess carrier concentration, absorption and surface recombination. In addition, a total internal reflection correction should also be included in the analysis, which leads to the MARS set of corrections. This method can be used for further quantification efforts that also should involve Monte Carlo calculations of the generation of excess carriers. 

By the total internal reflection condition at the liquid-liquid interface, one can observe interfacial reaction in the evanescent layer, a very thin layer of a ca. 100 nm thickness. Fluorometry is an effective method for a sensitive detection of interfacial species and their dynamics [10]. Time-resolved laser spectrofluorometry is a powerful tool for the elucidation of rapid dynamic phenomena at the interface [11]. Time-resolved total reflection fluorometry can be used for the evaluation of rotational relaxation time and the viscosity of the interface [12]. Laser excitation can produce excited states of adsorbed compound. Thus, the triplet-triplet absorption of interfacial species was observed at the interface [13]. 

In addition, typical methods of sensing are total internal reflection fluorescence or monitoring of fluorescence resonance energy transfer6,7. The second class is a direct optical detection principle which relies either on reflectometry or refractometry. The latter is connected to evanescent field... 

The methods of choice for the determination of acrylonitrile in environmental samples are GC/NPD (Page 1985), GC/FID (EPA 1982a), and GC/MS (EPA 1982b). Multiple internal reflectance infrared spectrometry (Jacobs and Syrjala 1978) is useful for monitoring low levels of acrylonitrile in air. 

Kawahara and Ballinger [53,57] has used their method to characterise a number of known and unknown petroleum samples. All of these studies used the normal transmission method to obtain infrared spectra however, the feasibility of using internal reflection to obtain infrared spectra has been demonstrated by several groups (Mattson and Mark [55], Mark et al. [58],... 

In this method, the sample (such as a polymer film) is pressed against a transparent material having a high refractive index (called the internal reflection element (IRE)). The IR light beam passes through this material, rather than air, before and after reflecting from the sample, hence the reason for describing... 

To put things into perspective, we. can broadly classify these analytical methods into bulk, dry surface, and in situ interfacial techniques. This chapter focuses on the last category, illustrating two in situ techniques used to study anion binding at the goethite (a-FeOOH)-water interface titration calorimetry and cylindrical internal reflection-Fourier transform infrared (CIR-FTIR) spectroscopy. In fact, CIR-FTIR could prove to be extremely powerful, since it allows direct spectroscopic observation of ions adsorbed at the mineral-water interface. 

M. N. Kronick and W. A. Little, A new immunoassay based on fluorescence excitation by internal reflection spectroscopy, J. Immtmol. Methods 8, 235-240 (1975). 

D. Axelrod, Total internal reflection fluorescence microscopy, in Fluorescence Microscopy of Living Cells in Culture B (D. L. Taylor and Y.-L. Wang, eds.), Methods in Cell Biology, Vol. 30, pp. 245-270, Academic Press, San Diego, California (1989). 

R. Lowe, V. Hlady, J. D. Andrade, and R. A. VanWagenen, Human haptoglobin adsorption by a total internal reflection fluorescence method, Biomaterials 7, 41-44 (1986). 

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