IR spectroscopy sample preparation

For IR spectroscopy, sample preparation has been a labour-intensive operation requiring some measure of skill and experience. Conventional IR spectroscopy is mainly based on transmission measurements except for samples for which the preparation of a thin layer is problematic, inadequate, or prohibited. In these cases special sample preparation is required as indicated in Section 5.1.1,5.1.2, etc. The main sampling techniques may be seen schematically in Figure 2. 

See also Fibre Optic Probes in Optical Spectroscopy, Clinical Applications IR Spectrometers IR Spectroscopy Sample Preparation Methods IR Spectroscopy, Theory Medical Science Applications of IR. 

See also Environmental and Agricultural Applications of Atomic Spectroscopy Environmental Applications of Electronic Spectroscopy Geology and Mineralogy, Applications of Atomic Spectroscopy Inorganic Compounds and Minerals Studied Using X-Ray Diffraction IR and Raman Spectroscopy Studies of Works of Art IR Spectroscopy Sample Preparation Methods MRI of Oil/Water in Rocks X-Ray Fluorescence Spectrometers. 

See also Biochemical Applications of Mass MS-MS and MS Organometallics Studied Using Spectrometry Fragmentation in Mass Spectrometry Mass Spectrometry Peptides and Proteins Studied Ion Energetics in Mass Spectrometry Ionization The- Using Mass Spectrometry Plasma Desorption loniza-ory IR Spectroscopy Sample Preparation Methods tion in Mass Spectrometry Spectroscopy of Ions. 

See also IR Spectrometers IR Spectroscopy Sample Preparation Methods IR Spectroscopy, Theory. 

See also ATR and Reflectance IR Spectroscopy, Applications Biochemical Applications of Raman Spectroscopy Food Science, Applications of Mass Spectrometry Food Science, Appiications of NMR Spectroscopy Fourier Transformation and Sampiing Theory FT-Raman Spectroscopy, Appiications iR Spectrometers, IR Spectroscopy Sample Preparation Methods IR Spectroscopy, Theory IR Spectral Group Frequencies of Organic Compounds Nonlinear Optical Properties Raman Optical Activity, Spectrometers Raman Spectrometers. 

See also Biochemical Applications of Raman Spectroscopy Far-IR Spectroscopy, Applications IR Spectroscopy, Theory IR Spectrometers IR Spectroscopy Sample Preparation Methods Raman Spectrometers Rayleigh Scattering and Raman Spectroscopy, Theory. 

IR Spectroscopy. Samples for IR spectroscopy were prepared by pressing 100-mg KBr pellets containing 1 mg of sample. Samples were run both on a Perkin-Elmer model 167 dispersive (grating) instrument and on a Perkin-Elmer model 1750 Fourier transform diffractometer-model 7300 laboratory computer system. Only the latter instrument afforded the resolution needed to identify the skeletal frequencies of isopropyl groups. 

Very often, samples for IR spectroscopy are prepared as solid state discs by grinding the compound for analysis with an alkali metal halide. Suggest why the IR spectra of K2[PtCl4] in KBr and KI discs might be different. 

Very often, samples for IR spectroscopy are prepared as solid state discs by grinding the compound for... 

The sample for IR spectroscopy was prepared when mixing metal/ carbon nanocomposite powder with 1 drop of vaselene oil in agate... 

The polymers were characterized by their compositions, intrinsic viscosities, crystallinities and nascent morphologies. Copolymer compositions were measured by IR spectroscopy. Samples were prepared by hot pressing about SOmg.of polymer between aluminium foil at 170 C and 100 kg x cm pressure during 60 s. After removal from the press, they were water-cooled to ambient temperature for about 5 min. Films of approximately lOOp thickness were annealed at 106 C under N2 for 168 h. in sealed tubes. The hexene contents (C ) in mol % were determined by calculation of the 3<> bion ratio and with... 

The sample for IR spectroscopy was prepared when mixing metal/carbon nanocomposite powder with one drop of vaselene oil in agate mortar to obtain a homogeneous paste with further investigation of the paste obtained on the appropriate instrument. As the vaselene oil was applied when the spectra were taken, we can expect strong bands in the range 2,750-2,950 cm. Two types of nanocomposites rather widely applied during the modification of various poly-... 

Rps. viridis RC were prepared according to standard procedures or by chromatofocusing (Welte et al., 1983). The RC were kept in a buffer containing 20 mM Tris pH 8 and 0.1 % LDAO. For time-resolved IR spectroscopy, samples were prepared as described in Hienerwadel et al. (1992), except that UQ-9 was added according to the procedure described in Breton et al. (1991b) and IS mM ferricyanide was added to oxidize the hemes. For steady-state Q /Q FTIR spectra, samples with sodium ascorbate and diaminodurene were prepared as described in Breton et aL (1991a,b). 

Sample preparation is straightforward for a scattering process such as Raman spectroscopy. Sample containers can be of glass or quartz, which are weak Raman scatterers, and aqueous solutions pose no problems. Raman microprobes have a spatial resolution of - 1 //m, much better than the diffraction limit imposed on ir microscopes (213). Eiber-optic probes can be used in process monitoring (214). 

For on-bead analysis vibrational spectroscopy (IR-spectroscopy) can be employed attenuated total reflection is a method allowing fast and nondestructive on-bead analysis of small samples (single bead analysis) without significant sample preparation. Solid phase NMR is the method of choice if complex structural analysis is intended on the support. Spatially resolved analysis on the resin is possible with microscopic techniques. 

ATR is one of the most useful and versatile sampling modes in IR spectroscopy. When radiation is internally reflected at the interface between a high-refractive index ATR crystal (usually Ge, ZnSe, Si, or diamond) and the sample, an evanescent wave penetrates inside the sample to a depth that depends on the wavelength, the refractive indices, and the incidence angle. Because the penetration depth is typically less than 2 pm, ATR provides surface specific information, which can be seen as an advantage or not if surface orientation differs from that of the bulk. It also allows one to study thick samples without preparation and can be used to characterize highly absorbing bands that are saturated in transmission measurements. 

Near-infrared spectroscopy is quickly becoming a preferred technique for the quantitative identification of an active component within a formulated tablet. In addition, the same spectroscopic measurement can be used to determine water content since the combination band of water displays a fairly large absorption band in the near-IR. In one such study [41] the concentration of ceftazidime pentahydrate and water content in physical mixtures has been determined. Due to the ease of sample preparation, near-IR spectra were collected on 20 samples, and subsequent calibration curves were constructed for active ingredient and water content. An interesting aspect of this study was the determination that the calibration samples must be representative of the production process. When calibration curves were constructed from laboratory samples only, significant prediction errors were noted. When, however, calibration curves were constructed from laboratory and production samples, realistic prediction values were determined ( 5%). 

Modern spectroscopy plays an important role in pharmaceutical analysis. Historically, spectroscopic techniques such as infrared (IR), nuclear magnetic resonance (NMR), and mass spectrometry (MS) were used primarily for characterization of drug substances and structure elucidation of synthetic impurities and degradation products. Because of the limitation in specificity (spectral and chemical interference) and sensitivity, spectroscopy alone has assumed a much less important role than chromatographic techniques in quantitative analytical applications. However, spectroscopy offers the significant advantages of simple sample preparation and expeditious operation. 

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