Use for Internal Reflection

As already pointed out, the FTIR technique is suitable for internal reflection experiments, on condition that reflectance accessories are used. This method was first developed in Austria by Neugebauer, Brinda-Konopik, and 

FIGURE 20. Schematic diagram of a polarization-modulated Fourier transform infrared spectrometer. After Kunimatsu et 

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FIGURE 11 Plate used for internal reflection spectroscopy. The lower drawing shows the sample in contact with the plate and radiation being multiply internally reflected within the plate. 

FIGURE 23. Schematic diagram of the electrochemical cell used for internal reflection, according to Ref. 52. 

Langmuir-Blodged films have been deposited on many different substrates. The substrates used include different types of glass (such as quartz for UV-visible spectroscopy) CaF2 plates for transmission infrared spectroscopy silicon, germanium, and ZnSe plates for internal reflection infrared spectroscopy. For electrochemical applications, LB films... 

The ATR technique is a commonly used infrared internal reflection sampling technique. It samples only the surface layer in contact with the ATR element the sampling depth probed is typically of the order of 0.3-3 pm [1]. Unless software corrected, compared with a transmission spectrum, the relative intensity of bands within an ATR spectrum increase in intensity with decreasing wavenumber. Several FTIR instrument companies now supply "ATR-correction" software developed to correct for the different relative intensities of bands observed between ATR and transmission spectra, so that ATR spectra can be more easily compared to and searched against transmission spectra. 

M. R. Rainbow, S. Arterton, and R. C. Eberhardt, Fluorescence lifetime measurements using total internal reflection fluorimetry Evidence for a conformational change adsorbed to quartz, J. Biomed. Mater. Res. 21, 539-555 (1987). 

Infrared spectroscopy. IR spectra were recorded on a Nicolet 5DX FT-IR spectrometer. A thin coating of the condensed silanes was applied on KBr pellets made from a very high purity KBr powder (J. T. Baker Chemical Co.). The spectra of these pellets were recorded using the transmission method. Liquid silanes were analyzed using the internal reflection attachment (IRA). The number of scans was chosen to be 20 for both background and samples. 

V. Hsieh and N. L. Thompson, Theory for measuring bivalent surface binding-kinetics using total internal-reflection with fluorescence photobleaching recovery, Biophys. J. 66, 898-911 (1994). 

Aslan K, Holley P, Geddes CD (2006) Microwave-accelerated metal-enhanced fluorescence (MAMEF) with silver colloids in 96-well plates Application to ultra fast and sensitive immunoassays, high throughput screening and dmg discovery. J Immunol Methods 312 137-147 Matveeva E, Gryczynski Z, Malicka J et al (2004) Metal-enhanced fluorescence immunoassays using total internal reflection and silver-coated surfaces. Anal Biochem 334 303-311 Blue R, Kent N, Polerecky L (2005) Platform for enhanced detection efficiency in luminescent-based sensors. Electron Lett 41 682-684... 

The utihzation of fluorescence dyes for analytical measurements enhances the sensitivity for the detection of the molecules of interest. First, Cronick and Little made use of evanescent wave excitation for a fluorescence immunoassay, in 1975. By using totally internally reflected light, they excited the fluorescence of a fluorescein-labeled antibody which has become bound to a hapten-protein conjugate adsorbed on a quartz-plate in an antibody solution [41]. Contrary to the label-free high-refractive-index sensors where the mass of the molecule of interest is... 

The increasing application of spectroscopic methods in electrochemistry has characterized the last decade and marked the beginning of new developments in electrochemical science [1]. Among these methods, in-situ infrared spectroscopy provides a very useful tool for characterizing the electrode-solution interface at a molecular level. First in-situ infrared (IR) electrochemical measurements were performed in 1966 [2] using the internal reflection form [3]. However, problems in obtaining very thin metal layers on the surface of the prisms used as IR windows, delayed the extensive application of in-situ IR spectroscopy until 1980, when the method was applied in the external reflection form [4]. The importance of this step does not need to be emphasized today. 

Intraexperiment Variability (Figure 5) The intraexperiment variability is evaluated by examining the variation in the replicate measures obtained within a given repeat experiment. This value is most useful for workers within a laboratory, since it is an indicator of the performance of a particular assay on a specific day. While useful for internal monitoring, this value does not provide a particularly good indication of how an assay performs over time. This is because replicate measures are obtained under conditions where sources of variability such as different technical staff, preparation of the test substances, preparation of cell cultures, and preparation of media are tightly controlled. Because of this control, results obtained from a group of replicate measures best represent a precise estimate of test variability at the particular time under the particular conditions when the test was run. It is not necessarily an accurate reflection of a test s performance over multiple runs. Thus, the performance of an assay over time within one laboratory is best measured at the level of the repeat experiment. 

Raman Spectroscopy. As mentioned earlier, the Raman effect is an emission phenomenon, which means that front-surface sampling is possible. An irregularly shaped solid may be used in the spectrometer without processing it to make it flat, as required for internal reflection, or without processing it to a film or powder for transmission IR. Another sampling convenience is that Raman is more easily applicable to water solutions than IR. 

As described in Section 3.1, Baier et al. (1974) have used a machined germanium prism to sample surface organic monolayers in the manner developed earlier by Blodgett (1934,1935) for fatty acid films. The basis of their analytical method, infrared spectroscopy by the technique of internal reflections inside the machined prisms, is only qualitative but serves very well to examine the chemical nature of the surface organics. It is well known that when an internal reflection prism made of a material with a sufficiently high index of refiraction such as germanium is used, the internal reflection IR spectrum obtained suffers no band distortion or band shift when compared to conventional transmission spectra of the same substance (Barr and Flournoy, 1969). 

Fishman and Erdmann (1971) have recently reviewed the topic of water analysis. Among the infrared methods mentioned were the following the use of internal reflection spectroscopy for the analysis of optically opaque samples the determination of total carbon in waste waters the quantitative determination of total CO2 in sea water the determination of the deuterium content in water the use of spectra of hydrocarbon fractions from the acid part of organic substances in natural waters and the use of infrared for the identification of organic substances in water. 

Why diamond Yes, it is hard, but it is its optical qualities (and great advertising) that have made it so popular. The refractive index of diamond is 2.42 while rutile (once proposed as a diamond simulant) and moissanite (now being used as such) have refractive indices of 2.6/2.9 and 2.65/2.69, respectively so it does not have the best optical properties (for internal reflection). 

The setup for internal reflection spectroscopy is shown in Kg. 3. The electrode consists of a germanium reflection element, covered on one side with PPy in contact with the electrolyte solution. The IR beam is totally reflected at the interface between the reflection element and the PPy layer. The penetration depth of the IR beam into the optical thinner medium (polymer and electrolyte) at each total reflection is in the order of some m. Spectral information on this small region is available without disturbances by the bulk electrolyte. Since the counter electrode and the reference electrode can be mounted in an advantageous arrangement, no electrochemical hmitations, connected with a thin electrolyte layei occur using this method. Due to the limited stability of Ge in aqueous electrochemical systems, the water content of the electrolyte solution has to be very low. 

Mulhouse, 12th-15th Sept.1994, p.346-9. 9(12)4 USE OF INTERNAL REFLECTION FTIR SPECTROSCOPY FOR BV-SITU STUDY OF WATER-POLYMER-SUBSTRATE SYSTEMS Linossier 1 Gaillard F Romand M Lyon,Universite Claude Bernard (Societe Francaise du Vide Institute of Materials Dechema Institut)... 

There are several reviews and books devoted to the theory and techniques of surface IR spectroscopy [100, 102, 117, 118]. The classical scheme proposed by Harrick uses an internal reflection element [100]. Later, the ATR method was developed to improve the surface sensitivity. The optimum conditions for recording ATR spectra and experimental techniques are described here in Chapters 2 and 4. 

The problan of signal selectivity of FTIR severely complicates the design and reduces the versatility of operando setups. A large number of cells for the study of liquid-solid EF.ls has been built and demonstrated in different reflectance modes (Fig. 7.4) [105,106, 109, 115, 119-122]. The material used as crystal (for internal reflection experiments) or transparent window (for external reflection experiments) needs to be carefully selected based on its chanical compatibility with the cell components. Insight into the formation of new products and the potentials at which... 

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