Internal reflection spectrometry

Mattson and Mark [55,56] reported some criticism of Kawahara s technique. They claim that evaporation of the solvent chloroform by infrared heating removes volatiles and causes large changes in the ratios. An oil sample was shown to suffer such alteration by the infrared during repeated analysis. The absorption of all bands decreased nonuniformly between 20 and 100% over a period of 30 min. They propose the application of internal reflection spectrometry as a rapid, direct qualitative technique requiring no sample pretreatment. 

N. J. Harrick and G. I. Loeb, Multiple internal reflection spectrometry, Anal, Chem, 45, 687-691 (1973). 

Adsorption of Proteins and Polysaccharides at Aqueous—Solid Interfaces by Infrared Internal Reflection Spectrometry In Situ Investigation... 

Hansen WN, Kuwana T et al (1966) Observation of electrode-solution interface by means of internal reflection spectrometry. Anal Chem 38(13) 1810-1821... 

Liquids are one of the easiest classes of materials to study quantitatively via single- or multi-reflection ATR because a well-defined contact surface is obtained. The particular advantage of ATR over conventional transmission for the study of liquids is that the requirements on the liquid cell can be relaxed, especially where small thicknesses are required for transmission measurements. Simpson [97] used HATR-FTIR for the multicomponent analysis of formulated oils. Internal reflection spectrometry can also be used to identify solutes in volatile solvents since the solvent can be readily evaporated, leaving the solute as a thin layer on the surface of the IRE. Repetitive analysis of liquid samples is made easy by the wipe on/wipe off sampling afforded by the horizontal ATR accessory. Table 1.14 lists the preferred accessories for various solid sample types. When both single-bounce and multi-bounce are indicated, single-bounce is more suitable for examining the main component multi-bounce qualifies for lower concentration components or weaker spectral features. 

Attenuated total reflection (ATR) has grown into the most widely practiced technique in infrared spectrometry. The reasons for this are fairly straightforward the technique requires little or no sample preparation, and consistent results can be obtained with relatively little care or expertise. The technique is not foolproof, but it can be very forgiving. ATR spectrometry is known by a number of alternative names, for example, multiple internal reflection (MIR), which is not to be confused with mid-infrared, frustrated multiple internal reflection (FMIR), evanescent wave spectrometry (EWS), frustrated total internal reflection (FTIR), which is not the same as Fourier transform infrared (FT-IR) spectrometry, and internal reflection spectrometry (IRS), but IRS is better known, at least in the United States, as the Internal Revenue Service. 

M.J.D. Low and R.T. Yang, "Quantitative Analysis of Aqueous Nitrite/Nitrite Solutions by Infrared Internal Reflectance Spectrometry". Anal. Chem., 45, 2014 (1973). 

Harrick, N. J., and N. H. Riederman, 1965. Infrared spectra of powders by means of internal reflection spectrometry. Spectrochim. Acta 21 2135. 

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. 

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. 

Schulten, H.-R., and Soldati, F. (1981). Identification of ginsenosides from Panax ginseng in fractions obtained by high-performance liquid chromatography by field desorption mass spectrometry, multiple internal reflection infrared spectroscopy and thin layer chromatography. J. Chromatogr. 212, 37-i9. 

Internal reflection spectroscopy is widely applied for on-line process control. In this type of application, the chemical reactor is equipped with an internal reflection probe or an IRE. The goal of this type of application is the quantification of reactant and/or product concentrations to provide real-time information about the conversion within the reactor. In comparison with other analytical methods such as gas chromatography, high-pressure liquid chromatography, mass spectrometry, and NMR spectroscopy, ATR spectroscopy is considerably faster and does not require withdrawal of sample, which can be detrimental for monitoring of labile compounds and for some other applications. 

Fig. 3. Total internal reflection cell used for the interfacial fluorescence lifetime measurement (left) and the external reflection absorption spectrometry (right).

Kolboe and Ellefsen (1962) and Michell et al. (1965) provided preliminary results indicating the feasibility of employing infrared spectroscopy to determine the lignin content of finely ground wood and pulp samples embedded in potassium chloride. Further development and refinement of this technique have led to methods for determination of lignin based on multiple internal reflectance infrared spectrometry (Marton and Sparks 1967) and diffuse reflectance Fourier transform spectrometry (Schultz et al. 1985). Lignin contents have also estimated by 13C CP/MAS/NMR spectrometry (Haw et al. 1984, Hemmingson and Newman 1985) (see Chap. 4.5). 

One disadvantage of films is that they may cause excessive light-scattering intransmittance spectrometry. This shortcoming can be overcome by using attenuated total-reflection or internal-reflection sampling techniques. 

Now as to the microtechniques which have proved useful for infrared spectrometry, there are several types available in the literature, such as microcells for solutions (9, JO), microgrooved plates for confined films 7,11), suspended particles on a membrane filter 12,13), microspecular spectrometry (14), the various micropellet procedures 15,16,17,18,19, 20, 21, 22, 23, 24, 25), and multiple internal reflectance (5,12,15,26,27). Then, of course, there is multiple scan interference spectrometry 28) with computer storage and handling of the data. It is with this technique... 

Surface Analysis Attenuated Total Internal Reflectance (ATIR), EDX, Rutherford Backscattering (RBS), Electron Spectroscopy for Chemical Analysis (ESCA) also known as X-ray Photoelectron Spectroscopy (XPS), Secondary Ion Mass Spectrometry (SIMS), Ion Scattering Spectroscopy (ISS)... 

Surface characterization by spectroscopic techniques yields information on the functional groups and elemental composition on the surface of polymeric biomaterials. The most common spectroscopic tools used for biomedical polymers are X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), and Fourier transform infrared spectroscopy (FTIR) (diffuse reflectance and attenuated total internal reflectance modes). Each of these techniques is discussed in the succeeding text. 

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