Solid sample analysis using FTIR

Simethicone is an antigas ingredient in many liquid and solid pharmaceutical preparations, and FTIR is used in quality assurance laboratories to determine whether its concentration is at the specified level. A sample of the product is dispersed in an HC1 solution and the simethicone extracted from this solution with toluene. The toluene solutions are then run on the FTIR using a liquid sampling cell. For the quantitative analysis, a simethicone absorption band that is free from interference from the toluene absorption bands is used in a manner similar to that of the isopropyl alcohol band in Experiment 26. 

It is necessary to be able to identify and quantify the additives in polymers and vibrational spectroscopy is a particularly useful approach to this problem. Compared with traditional chemical analyses, vibrational methods are nondestructive and are time-and cost-effective as well as more precise. A large number of examples exist in the literature. For example, antistatic agents (polyethylene glycol (PEG) in polyethylene (PE)) can be detected directly using FTIR sampling (367). An IR spectroscopic technique for the analysis of stabilisers (2, 6-di-tert-butyM-methylphenol) in PE and ethylene-vinyl acetate (EVA) copolymer has been described (368). It is possible to quantify the amount of external and internal lubricants (stearic acid in polystyrene (PS)) (371). Fillers in polymers can also be analysed (white rice husk ash (predominantly silica in polypropylene (PP)) (268). Raman spectroscopy has been used to detect residual monomer in solid polymethyl methacrylate (PMMA) samples (326). 

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. 

Principles and Characteristics As already indicated in Chp. 1.2.3, Raman scattering induced by radiation (UV/VIS/NIR lasers) in gas, liquid or solid samples contains information about molecular vibrations. Raman specfioscopy (RS) was restricted for a long time primarily to academic research and was a technique rarely used outside the research laboratory. Within an industrial spectroscopy laboratory, two of the more significant advances in recent years have been the allying of FT-Raman and FTIR capabilities, coupled with the availability of multivariate data analysis software. Raman process control (in-line, on-line, in situ, onsite) is now taking off with various robust commercial instrumental systems equipped with stable laser sources, stable and sensitive CCD detectors, inexpensive fibre optics, etc. With easy interfacing with process streams and easy multiplexing with normal (remote) spectrometers the technique is expected to have impact on product and process quality. 

Cr-ZSM-5 catalysts prepared by solid-state reaction from different chromium precursors (acetate, chloride, nitrate, sulphate and ammonium dichromate) were studied in the selective ammoxidation of ethylene to acetonitrile. Cr-ZSM-5 catalysts were characterized by chemical analysis, X-ray powder diffraction, FTIR (1500-400 cm 1), N2 physisorption (BET), 27A1 MAS NMR, UV-Visible spectroscopy, NH3-TPD and H2-TPR. For all samples, UV-Visible spectroscopy and H2-TPR results confirmed that both Cr(VI) ions and Cr(III) oxide coexist. TPD of ammonia showed that from the chromium incorporation, it results strong Lewis acid sites formation at the detriment of the initial Bronsted acid sites. The catalyst issued from chromium chloride showed higher activity and selectivity toward acetonitrile. This activity can be assigned to the nature of chromium species formed using this precursor. In general, C r6+ species seem to play a key role in the ammoxidation reaction but Cr203 oxide enhances the deep oxidation. 

TG-FT-IR, Pyrolysis analyses were performed on the preliquefaction solids using thermogravimetric (TG) analysis with on-line analysis of the evolved products (including an infrared spectrum of the condensables) by FT-IR. The TG-FTIR method has been described previously (23-25). The Bomem TG/plus instrument was employed. A sample is continuously weighed while it is heated. A flow of helium sweeps the products into a multi-pass cell for FT-IR analysis. Quantitative analysis of up to 20 gas species is performed on line. Quantitation of the tar species is performed by comparison with the balance reading. 

FTIR spectroscopy may be applied to good advantage in such specialized areas as micro analysis where high sensitivity is required, in the analysis of aqueous solutions or dark, solid state samples that require the use of special reflectance techniques, in investigations placing emphasis on quantitative evaluation, and in experiments where analysis time is a limiting factor, e.g., in process or quality control measurements. 

Preparation and Characterization of Lanthanide and Actinide Solids. Standard crystalline lanthanide and actinide phosphates were prepared by literature procedures (16-18) and characterized by X-ray powder diffraction, FTIR spectroscopy, and thermogravimetric analysis (TGA). Europium was used as an analogue of the trivalent actinides. Metal-phytate solids were generated by mixing Eu(III), U(VI), or Th(IV) nitrate solutions with 0.1 M phytic acid at pH 5 and metal.phytate ratios of 1 1 2 1, and 4 1. The metal phytates precipitated immediately. The resulting slurries were stirred at 85 °C for 30 days and sampled periodically for analysis of the solids by TGA, X-ray powder diffraction, and FTIR. The rate of phosphate release to the solution was monitored colorimetrically. 

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