Potassium bromide pellets preparation

A potassium bromide pellet prepared from the major component indicated the formation of an ester linkage, the presence of a phosphate, and an A -t-butoxycarbonyl group. A UV spectrum with a maximum absorption at 257.5 nm identical to that of ATP eliminated the possibility that aminoacylation may have taken place at 6-amino group of nucleotide. Nuclear magnetic resonance spectroscopy demonstrated the presence of tertiary butyl protons. On the basis of the above evidence, structure (II) has been assigned to this product. 

Normal glass will only transmit radiation between about 350 nm and 3 /rm and, as a result, its use is restricted to the visible and near infrared regions of the spectrum. Materials suitable for the ultraviolet region include quartz and fused silica (Figure 2.28). The choice of materials for use in the infrared region presents some problems and most are alkali metal halides or alkaline earth metal halides, which are soft and susceptible to attack by water, e.g. rock salt and potassium bromide. Samples are often dissolved in suitable organic solvents, e.g. carbon tetrachloride or carbon disulphide, but when this is not possible or convenient, a mixture of the solid sample with potassium bromide is prepared and pressed into a disc-shaped pellet which is placed in the light path. 

The infrared spectrum, for a sample prepared as a potassium bromide pellet, is highly characteristic of the compound. The spectrum is shown in Figure 6 and Table 3 lists the band assigiunents. 

The infrared spectra of the coal and the various extracts were recorded on a Baird, Model GY-1 (Ireland Mine vitrain concentrate) and on a Perkin Elmer Model 337 spectrophotometer (Bruceton coal). The samples were prepared by the potassium bromide pellet technique. The high resolution proton NMR spectrum of the benzene soluble extract from Ireland Mine vitrain concentrate was recorded on a Varian A-60 spectrometer in 10% deuterated chloroform (CDCh) solution, using tetrametnylsilane internal standard. 

Fourier transform infrared spectroscopy (FTIR) was also used to monitor the degree of pyrolysis for various samples at different temperatures. The KBr (potassium bromide) pellet of sample was prepared for FTIR analysis. 

Figure 2. Equipment useful in preparing micro potassium bromide pellets...

Polycrystalline or powdered samples can be prepared as a suspension in mineral oil (Nujol mull), as a potassium bromide disk (pellet), or as thin films deposited on infrared-transparent substrates. The potassium bromide pellet is the most common way of preparing powder samples in this method a small amount, usually 1 mg, of finely-ground solid sample is mixed with powdered potassium bromide, usually 300 mg. and then pressed in an evacuated die under high pressure. The resulting disks are transparent and yield excellent spectra. The only infrared absorption in the potassium bromide matrix is due to small amounts of adsorbed water, which can. however, be confused with OH-containing impurities in the sam-... 

Based on this finding, they proposed a method for determining the tacticity of amorphous samples of PVC. Because some samples cannot be easily transformed into an amorphous state, Schneider and co-workers [68] devised an IR method of tacticity determination which is independent of sample crystallinity. From the temperature dependence of IR spectra of PVC samples prepared by different methods, the intensity of the band at 14.40 pm (proportional to the number of isotactic diads in the sample), as well as that of the tacticity-independent C-H stretching band, was found to be independent of sample crystallinity. These lines were applied to the tacticity determination in PVC, measnred in potassium bromide pellets. The numerical tacticity value was obtained from the known values of absorbance coefficients of S h and S h type C-Cl stretching bands in solution, and from the shape of the spectrum. 

Diffuse internal reflectance (DRIFT). DRIFT uses potassium bromide pellets for sample preparation and, therefore, has certain limitations in use with hygroscopic materials. 

Meloche, V. W., and G. E. Kalbus, 1958. Anomalies in the infrared spectra of inorganic compounds prepared by the potassium bromide pellet technique. J, Inorg. Nucl. Chem. 6 104. 

Infrared spectroscopy is a relatively simple technique, nondestructive, and versatile enough to analyze solids, liquids, and gases with a minimum of sample preparation. Polymers can be mixed with potassium bromide and then pressed into pellets. Films can be prepared from melt or cast from solution and can be studied easily. In bulk samples or powders, or if a concentration profile is needed, the reflectance technique is probably more suitable than transmission. 

The solutions for measuring total available oil are stable and can be prepared in advance. The weight of the sample is important, especially for the dryer samples, press cake, and pellets. These samples absorb a lot of water. Furthermore, the concentration of the potassium bromide solution may need to be decreased if a sample has an extremely low level of limonene (i.e., press liquor or pellets). 

Finally release the press and remove the die body (A) and the upper steel pellet from the face of the disc and then remove the disc itself with tweezers (the disc should never be handled with the fingers), and mount it in the specially designed holder. These latter operations are best conducted under a radiant heater. The disc holder is located in position in the sample beam path of the spectrophotometer if required a blank potassium bromide disc, similarly prepared, is introduced into the reference beam path. 

Test 3 Examine by infrared absorption spectrophotometry, comparing with the spectrum obtained with dipyridamole CRS. Examine the substances as pellets prepared using potassium bromide R. 

Dispersed in an infrared transparent powder. Pellets are made with I to 2% by weight of the sample, usually in dry potassium bromide. A pellet of approximately 300 mg is prepared in a mould called a matrix using a laboratory press. This method produces pellets 1 to 2 mm thick for a diameter of approximately 13 mm. This technique can be used for quantitative studies but the spectra may sometimes differ ftom those obtained via dispersion in a liquid. This is because, under the effect of the high pressure to which the powder is subjected, the solid may undergo certain modifications. 

The sample and potassium bromide should be weighed on an analytical balance the first few times that a pellet is prepared. After some experience, you can estimate these quantities quite accurately by eye. 

Potassium bromide is extremely hygroscopic, so it should be stored in a tightly capped bottle in a desiccator except when needed for preparation of a pellet. Even with the greatest precautions, it is difficult to prepare a pellet that is completely free of water. Possible contamination of a KBr pellet with water may cause problems in interpreting IR absorptions in the range 3600-3200 cm ... 

Is the polymer matrix as claimed Infra-red analysis is a good technique for this determination. IR spectra can be obtained quickly with minimum sample preparation. Liquids and films can be run directly. The dust from filing a solid sample can be ground with potassium bromide (KBr) and a pellet pressed for analysis. Is the additive readily apparent in the spectrum ... 

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