Cylindrical internal reflectance spectroscopy

The stability of phosphine-substituted Co clusters derived from Co4(CO)10(/r4-PPh)2 was examined under hydroformylation conditions using cylindrical internal reflectance (CIR) spectroscopy.148 [(CO)4Fe(//-PtBu2)Rh(CO)L], PPN[(CO)3CoO/-P(CMe3)2)Rh(CO)(HP(CMe3)2)], and... 

Characterization of Anion Binding on Goethite Using Titration Calorimetry and Cylindrical Internal Reflection-Fourier Transform Infrared Spectroscopy... 

Titration calorimetry and cylindrical internal reflection-Fourier transform infrared (CIR-FTIR) spectroscopy are two techniques which have seldom been applied to study reactions at the solid-liquid interface. In this paper, we describe these two techniques and their application to the investigation of salicylate ion adsorption in aqueous goethite (a-FeOOH) suspensions from pH 4 to 7. Evidence suggests that salicylate adsorbs on goethite by forming a chelate structure in which each salicylate ion replaces two hydroxyls attached to a single iron atom at the surface. 

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. 

Cylindrical. Internal Reflection - Fourier Transform Infrared (CIR-FTIR) Spectroscopy... 

The ATR technique is now routinely used for IR spectroscopy as it allows measurement of spectra for a variety of sample types with minimal preparation. The crystals employed are generally prismatic in shape, allowing contact of a flat surface with the sample. The ATR method was first adapted for HP IR spectroscopy by Moser [29-33], who realised that a conventional autoclave could easily be adapted for in situ IR spectroscopy by fitting an ATR crystal of cylindrical cross section. The technique developed by Moser is thus known as cylindrical internal reflectance (CIR) spectroscopy and high pressure cells based upon the CIR method have been commercialised by Spectra-Tech. A typical CIR cell is illustrated in Figure 3.8. 

An infrared spectrum is a plot of percent radiation absorbed versus the frequency of the incident radiation given in wavenumbers (cm ) or in wave length ( xm). A variation of this method, diffuse reflectance spectroscopy, is used for samples with poor transmittance, e.g. cubic hematite crystals. Increased resolution and sensitivity as well as more rapid collection of data is provided by Fourier-transform-IR (FTIR), which averages a large number of spectra. Another IR technique makes use of attenuated total reflectance FTIR (ATR-FTIR) often using a cylindrical internal reflectance cell (CIR) (e.g. Tejedor-Tejedor Anderson, 1986). ATR enables wet systems and adsorbing species to be studied in situ. 

Tejedor-Tejedor, M.L Yost, E.C. Anderson, M.C. (1990a) Characterization of benzoic acid and phenolic complexes at the goethite/ aqueous solution interface using cylindrical internal reflectance Fourier transform infrared spectroscopy. Part 5 Methodology. Langmuir 6 979-987... 

Historically, high-pressure IR spectroscopy has been one of the most important methods to measure intermediates or resting-state species in catalytic cycles. In 1%8, Wilkinson observed HRh(PPh3)2(CO)2 in the Rh/PPh3 catalyst system by IR spectroscopy where an IR cell was connected via a tube to the autoclave. A related study was performed more recently by Moser et who applied their cylindrical internal reflectance IR cell. They determined the rate-... 

Holmen B. A., Tejedor-Tejedor M. I., and Casey W. H. (1997) Hydroxamate complexes in solution and at the goethite-water interface a cylindrical internal reflection Fourier transform infrared spectroscopy study. Langmuir 13, 2197-2206. 

Characterization of Aquatic Humic and Fulvic Materials by Cylindrical Internal Reflectance Infrared Spectroscopy... 

Cylindrical internal reflectance infrared spectroscopy presents many advantages over conventional infrared techniques for the study of aquatic humic and fulvic materials. Samples can be studied in their natural state and in the aqueous environment from which they are isolated. Sample alterations due to drying and exposure to high pressures in the pellet forming process are avoided. In addition. 

Zeltner, W.A. et al.. Characterization of anion binding on goethite using titration calorimetry and cylindrical internal reflection-Fourier transform infrared spectroscopy, ACS Symp. Ser., 323, 142, 1986. 

Zeltner, W. A., E. C. Yost, M. L. Machesky, M. I. Tejedor-Tejedor, and M. A. Anderson (1986), Characterization of Anion Binding on Goethite Using Titration Calorimetry and Cylindrical Internal Reflection Fourier Transform Infrared Spectroscopy, Geochemical Processes at Mineral Surfaces, J. A. Davis and K. F. Hayes, Eds. (ACS Symposium Series No. 323), American Chemical Society, Washington, DC. 

The techniques of Cylindrical Internal Reflectance (CIR) and Diffuse Reflectance spectroscopies are described herein. The CIR phenomenon was employed in three different apparatus. Two different high pressure CIR cells were used to study reactions homogeneously catalyzed by [y-HW2(CO)10]-. Low temperature reactions of Mo and W complexes were studied using an ambient pressure CIR cell. The diffuse reflectance technique was employed to study powdered samples of Ru carbonyl complexes supported on A1203. 

Tejedor-Tejedor, M. I., Yost, E. C., and Anderson, M. A., Characterization of benzoic complexes at the goethite/aqueous solution interface using cylindrical internal reflection Fourier transform infrared spectroscopy. Part I. Methodology, Langmuir, 6, 980-987 (1990). 

FIGURE 12.15 The adsorption of PO4" by monodomainic goethite used by Hiemstra and Van Riemsdijk (1996) and that of Bowden et aL (1980). The lines are calculated with the charge distribution model and are consistent with the surface species observed by cylindrical internal reflection-Fourier transform infrared spectroscopy. (Reprinted from Journal of Colloid and Interface Science, 179, Hiemstra, T. and Van Riemsdijk, W. H. 488-508. Copyright 1996, with permission from Elsevier.)... 

ATR accessories for the measurement of liquids are not restricted to IREs with a trapezoidal or parallelpiped geometry. Alternatively, liquids can be measured with cylindrical IREs. A cylindrical internal reflection element is a rod that has a cone at each end, as shown in Figure 15.10. The cone typically has a 45° half-angle at the apex. The IRE is sealed into a liquid cell that exposes most of the rod to the liquid, and only the ends of the cell extend beyond the cell. Two geometries for cylindrical IREs are shown in Figure 15.11. The first (Figme 15.11a) is the CIRCLE cell (Thermo Spectroscopy Division, Madison, Wisconsin), where CIRCLE is an... 

Figs. 3.5-8 e - h show sample facilities for solids and powders which employ different multiple reflection arrangements. Conical arrangements of powders were used for Raman spectroscopy long ago (Brandmiiller and Moser, 1962). These devices make use of the advantages of multiple reflection and refraction at the surfaces of the grains in a powder. A multiple reflection system may be equipped with a metal mirror, like the cone-shaped indentation of the metal block shown in Fig. 3.5-8 e. Any flat sample whose surface is to be investigated may be placed on top of the mirror. Fig. 3.5-8 f shows a tablet with a conical or cylindrical bore in which multiple reflection at the internal surface of the sample occurs. 

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