IR microspectroscopy

Infrared microscopy is well suited for in situ analysis of contaminants fount in pharmaceutical processes. Due to the nondestructive nature of the analysis further experiments such as energy dispersive x-ray analysis may be performer on the same sample once IR investigations are complete. To illustrate the potentia of IR microspectroscopy, one application from the Bristol-Myers Squibl laboratories is presented. 

FT-IR microspectroscopy is a new nondestructive, fast and rehable technique for solid-phase reaction monitoring. It is the most powerful of the currently available IR methods as it usually requires only a single bead for analysis, thus it is referred to as single bead FT-IR [166]. (See also Chapter 12 for further details). The high sensitivity of the FT-IR microscope is achieved thanks to the use of an expensive liquid nitrogen-cooled mercury cadmium telluride (MCT) detector. Despite the high cost of the instrument, this technique should become more widely used in the future as it represents the most convenient real-time reaction monitoring tool in SPOS [166, 167]. 

Mouille, G., Robin S., Lecomte, M., Pagant S., and Hofte, H., 2003, Classification and identification of Arabidopsis cell wall mutants using Fourier-Transform InfraRed (FT-IR) microspectroscopy, Plant J. 35 393-404. 

Table 3.1 Electron source size, electron energy in the storage ring and maximum operating current for some synchrotron facilities where IR microspectroscopy beamlines are under operation or construction ( ) of low fS values...

Yan B, Gstach H, An indazole synthesis on solid phase support monitored by single bead FT-IR microspectroscopy, 37(46) 8325—8328, 1996. 

Another objective of this chapter is to introduce the use of Fourier transform infrared (FT-IR) microspectroscopy for the analysis of pigments and to provide some background about the technique. 

Samples that were organic in nature were subjected to the microchemical tests described by Hofenk-de Graaff (24) and subsequently analyzed by FT-IR microspectroscopy. 

Another example of pigment identification by IR microspectroscopy is shown in Figure 10. The bottom spectrum was obtained from a blue pigment from MS 972 (Archaic Mark) the top spectrum is a reference spectrum of Prussian blue. The band corresponding to the C=N of ferric ferrocyanide is common to both spectra. Replicate spectra of blue pigments removed from different locations in MS 972 indicate that the average frequency of this band is 2083 6 cm"1. The ubiquitousness of an iron blue in this manuscript raises doubts about the authenticity of this manuscript. 

Treatment of resin-bound a-arylazobenzhydryl 488 with a Lewis acid at room temperature followed by acidic cleavage furnished indazole 489 in quantitative yield, the reaction being monitored by single bead IR microspectroscopy (Equation 98) <1996TL8325>. Unsymmetrical azines 490 thermally cyclized to fused pyrazoles 491 (Equation 99) <2002TL6431>. Indazoles 493 were obtained from thermal cyclizations of (2-alkynylphenyl)triazenes 492 in the presence of methyl iodide as a solvent other solvents were tested where either no reaction or complex mixture of products was obtained (Equation 100) <2002JOC6395>. 

As described in the following sections, IR and Raman spectroscopy, using modem Fourier transform techniques such as IR microspectroscopy, offer excellent analytical tools for the burgeoning field of combinatorial chemistry. 

In the combinatorial chemistry laboratory, IR microspectroscopy lends itself to monitoring reaction products and reaction kinetics directly on a single resin bead (12) without having to cleave the molecule from the bead. 

A general advantage of Raman spectroscopy is the extended spectral range, and the Stokes shift (2) in FT-Raman spectra is usually recorded from 3500 to 50 cnr1. Like IR internal reflection spectroscopy (see Sec. Ill) and IR microspectroscopy (see Sec. IV), Raman spectroscopy is a nondestructive technique requiring little or no sample preparation. 

While IR transmission spectroscopy is a general analytical method for resin samples, internal reflection spectroscopy is especially suited for solid polymer substrates known as pins or crowns. Single-bead analysis is best done by IR microspectroscopy, whereas photoacoustic spectroscopy allows totally nondestructive analysis of resin samples. 

Provided that samples can be removed from the laboratory, there are two alternative sources of infrared radiation that are far better than incandescent sources for mid-IR microspectroscopy, namely the synchrotron and the free electron laser (FEE) [16]. 

Fabian, H., Thi, N.A.N., Eiden, M., Lasch, P., Schmidt,). and Naumann, D. (2006) Diagnosing benign and malignant lesions in breast tissue sections by using IR microspectroscopy, Biochim. Biophys. Acta, 178, 874-82. 

Lasch, P., Haensch, W., Naumann, D. and Diem, M. (2004) Imaging of colorectal adenocarcinoma using FT-IR microspectroscopy and cluster analysis. Biochim. Biophys. Acta, 1688,176-86. 

LeVine, S.M. and Wetzel, D.L. (1998) Chemical analysis of multiple sclerosis Lesions by FT-IR microspectroscopy. Free Radio. Biol Med., 25, 33 1. 

D. (2005) FT-IR-microspectroscopy of prion-infected nervous tissue. Biochim. Biophys. Acta, 1758, 948-59. 

Dukor, R.K., liebman, M.N. and Johnson, B.L (1998) A new, non-destructive method for analysis of clinical samples with FT-IR microspectroscopy. Breast cancer tissue as an example. Cdl. Mol. Biol, 44, 211-17. 

Tfalyli, A., Piot, 0., Durlach, A., Bernard, P. and Manfait, M. (2005) Discriminating nevus and melanoma on paraffin-embedded skin biopsies using FT-IR microspectroscopy. Biochim. Eiophys. 

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