Infrared spectroscopy mulls

The compression of a solid to transparency is really not new. A standard technique in infrared spectroscopy is the use of mulls made of the heavier alkali halides. These materials are squeezed transparent at relatively low pressures. However, when these low pressures are used, evacuation of the sample is essential. In our work, evacuation is not necessary. A reasonable review of the alkali halide work is given by Ford, Wilkinson, and Price (4). 

Frequencies are given in cm". Unless noted otherwise, frequencies were determined by infrared spectroscopy for nujol mull samples. 

Infrared spectra can be determined on neat (undiluted) liquids, on solutions with an appropriate solvent, and on solids as mulls and KBr pellets. Glass is opaque to infrared radiation therefore, the sample and reference cells used in infrared spectroscopy are sodium chloride plates. The sodium chloride plates are fragile and can be attacked by moisture. Handle only by the edges. 

A major difference between infrared and ultraviolet spectroscopy is in the concentrations required for assay In infrared spectroscopy as much as a 10% w/v solution of sample must be prepared. This means that the path length of the cells used in infrared must be very short, usually 0.025-0.1 mm (otherwise absorbance values would be too high). Another problem with infrared spectra is that the solvent used in the assay (usually chloroform or dichloromethane) also possesses chemical bonds that will absorb infrared radiation in some part of the spectrum, obscuring the absorption by the sample at these wavelengths. Samples are prepared in solution, in a mull or paste made with liquid paraffin (Nujol), or in a solid disc prepared by trituration with dry potassium bromide followed by compression in a hydraulic press. 

Identification of a drug substance is the fingerprinting of a drug material. This ensures that the correct material is utilized for biological testing, pharmaceutical investigation, and production. Infrared spectroscopy (Avith KBr pellet or Nujol mull) is commonly used for this purpose. UV spectroscopy Avith the material tested in aqueous or alcoholic solution is a convenient method of identification. 

A red-brown amorphous complex ZrCl4 2C4H4S was isolated from the reaction of the tetrahalide in excess thiophene. The compound does not dissolve in benzene, carbon tetrachloride, or hexane (411). A dimethylsulfide adduct, (CH3)2S-ZrCl4 has been examined by infrared spectroscopy, but no details of the preparation have been given (152). In a Nujol mull it shows two bands, one weak one at 372, and a second broad band at 299 cm . ... 

There are three general methods available for examining solid samples in transmission infrared spectroscopy, i.e, the use of alkali halide discs, mulls or films. Your choice of method depends very much on the nature of the sample to be examined. 

Solid mixtures can also be analysed by using infrared spectroscopy. However, solids are more susceptible to errors because of scattering effects. Such analyses are usually carried out with KBr discs or with mulls. The problem here is the difficulty in measuring the pathlength. However, this measurement becomes unnecessary when an internal standard is used. Addition of a constant known amount of an internal standard is made to all samples and calibration standards. 

The deactivated catalyst was studied by several methods scanning electron microscopy (SEM)-energy dispersive spectroscopy (EDS), infrared spectroscopy (IR), and by extracting water-insoluble phosphorus. The SEM-EDS studies gave no useful results. IR absorption was measured on samples that were mulled in mineral oil. Comparisons of IR spectra were made with samples of y -alumina and aluminum phosphate. Determination of total P in the deactivated sample, presumed to be present as water-insoluble aluminum phosphate, was made by standard wet chemical analysis dissolution in hot, dilute HCl followed by colorimetric determination of phosphate. ... 

Infrared spectroscopy is the fastest and cheapest of the spectroscopic techniques used by organie and polymer chemists. As indicated, it is the measurement of the absorption of IR frequencies by organic compounds placed in the path of the beam of light. The samples can be solids, liquids, or gases and can be measured in solution or as neat liquid mulled with potassium bromide (KBr) or mineral oil. Recent developments in attenuated total refleetion (ATR) and diffuse reflectance techniques have made the analysis of solid adhesives possible. In fact, for bulk samples or powders, the reflectance technique is probably more suitable than transmission. 

The proper preparation of a mull or paste is an excellent way to get a sample ready for qualitative infrared spectroscopy. One grinds vigorously about 3 to 10 mg of substance with a hard pestle in a hard and smooth mortar (e.g., agate) for 1 to 5 minutes until the powder is so fine that its caked surface takes on a glossy appearance. Then a small drop of mulling fluid is added, and the vigorous grinding... 

Katon et al. (1967 1969) used liquid-nitrogen temperature to investigate the detailed structure of crystalline sugars and the usefulness of infrared spectroscopy in the differentiation of sugars. Some of their spectra cover the range from 4000 to 33 cm" Figure 3.17 shows the infrared spectrum of a,a-trehalose dihydrate at both room temperature and 113°K recorded from a Nujol mull. (Similar results are... 

In 1950, Kuhn recorded the spectra of many carbohydrates, ten of which were crystalline sugars in Nujol mulls. Except for a-o-glucose, the type of anomer used was not mentioned. Nor did Urbanski et al. (1959) specify anomeric form when they recorded the spectra of six sugars. Tipson and Isbell (1962) have since identified these compounds by comparing their spectra with those of authentic anomeric forms of those sugars. Such studies for the identification of compounds are among the most common applications of infrared spectroscopy. 

Zugaza and Hidalgo (1965) studied the infrared spectroscopy of a variety of penicillins—natural, biosynthetic, and synthetic—in the form of mulls, pellets, and... 

Figure 2.11 Infrared spectrum of a mull (cf. SAQ 2.3). From Stuart, B., Modem Infrared Spectroscopy, ACOL Series, Wiley, Chicheste, UK, 1996. University of Greenwich, and reproduced by permission of the UnivCTsity of Greenwich.

An extensive literature on the infrared (ir) spectra of polymers exists (Zbinden, 1964 Henniker, 1967). Fortunately the ir spectra of functional groups anchored on polymers do not differ appreciably from those in small molecules, and the technique of taking the spectra of polymeric solids (film, mull, or KBr pellet) is well-developed. The sensitivity attained is approximately the same as that with the small molecules. Infrared spectroscopy has been particularly useful in following polymeric transformations. The characteristic absorption due to a particular functional group often disappears completely on chemical transformation, with a simultaneous appearance of the characteristic absorption of the new group(s). Thus, the completion of a reaction can be easily followed by scanning the ir spectra of reactant and product. Letsinger er aL (1964), Blackburn et aL (1969), and Farrall and Frechet (1976) have made extensive use of ir spectra to follow chemical transformations in polymers. 

Infrared spectroscopy work and ATR studies were carried out by Mr. John P. Falzone of these laboratories. ESCA experiments were carried out by Dr. J.S. Brinen and Mr. W. R. Doughman anodization experiments by Dr. T. B. Reddy and Ms. L. Maxine Mull. 

K. B. Bradley and W. J. Potts, Jr., The Internally Standardized Nujol Mull as a Method of Quantitative Infrared Spectroscopy, Appl. Spectroscopy 12, 77-80, 1958. 

A. Crook and P. J. Taylor, Simple Mulling Technique for the Preparation of Samples for Infrared Spectroscopy, Chem. 4 Ind. (London) 95,1955. 

Infrared spectra were recorded on a Perkin Elmer model 680 spectrophotometer as mulls in nujol or fluorolube. The magnetic susceptibility of the copper complexes was measured from 4.2 to 300 K by the Faraday method . X-ray photoelectron spectroscopy (XPS) was performed with a Perkin Elmer hemispherical spectrometer. 

Abstract—The nature of the product of the reaction between an aminated silane and carbon dioxide was re-examined with the aid of simple model compounds, several amines, and several aminosilanes. Since the reaction products previously proposed include the amine bicarbonate and a carbamate derived from the amine, ammonium bicarbonate and ammonium carbamate were studied as models for the anions. Carbon dioxide adducts of neat model amines were prepared and studied. Results from a variety of techniques are summarized. Among the most useful was Fourier transform infrared (FTIR) spectroscopy of fluorolube mulls. FTIR spectra were distinctive and assignments characteristic of the two species were extracted from the spectral data. Comparisons of these assignments with the products of the reaction between carbon dioxide and various amines were made. The results indicate that alkylammonium carbamates are the principal product. Nuclear magnetic resonance (NMR) spectra in D20 indicated much dissociation and were not helpful in defining the products. 

A number of experimental alternatives to traditional IR transmission spectroscopy are suitable for overcoming some of these complicating experimental factors. In the technique of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) (Hartauer et al. 1992 Neville et al. 1992) the sample is dispersed in a matrix of powdered alkali halide, a procedure which is less likely to lead to polymorphic transformations or loss of solvent than the more aggressive grinding necessary for mull preparation or pressure required to make a pellet (Roston et al. 1993). For these reasons, Threlfall (1995) suggests that DRIFTS should be the method of choice for the initial IR examination of polymorphs. He has also discussed the possible use of attenuated total reflection (ATR) methods in the examination of polymorphs and provided a comparison and discussion of the results obtained on sulphathiazole polymorphs from spectra run on KBr disks, Nujol mulls and ATR. 

Raman provides easy sampling, whereas IR spectroscopy frequently needs some form of sample preparation. Materials which are difficult to handle in IR (highly viscous liquids, solids requiring pellets, mulls, or diffuse reflectance) are often easily measured by Raman. Unlike IR reflectance spectra, Raman spectra of solid samples are not affected by sample properties such as particle size. A significant difference with infrared absorption spectroscopy is that the Raman signal is emitted from the sample. Consequently, matrix effects are seldom as severe in RS as they are with mid-IR and NIR. Water may be used as a solvent with no loss in signal or resolution. Glass, even tinted, does not interfere with the Raman spectra. 

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