IR-spectrophotometer

NMR spectra were recorded on a JEOL FX90Q (90 MHz) spectrometer. chemical shifts are reported relative to an internal standard of CHCI3 in CDCI3, while 13c chemical shifts are reported relative to the CDCI3 used as solvent. Infrared spectra were recorded on an IBM IR32 FTIR or a Perkin-Elmer 1330 IR spectrophotometer. Uv-visible spectra were obtained using a Varian DMS90 spectrophotometer. 

Spectra of solution cast films of the hydrogenated NBR were recorded on a Nicolet 520 FT-IR spectrophotometer. The final degree of olefin conversion was confirmed by infrared analysis.9... 

Methods. FTIR spectra were obtained in nujol mull on a Perkin Elmer model No. 1700GC-IR spectrophotometer. 1H NMR spectra were obtained at 363 MHz. 13C NMR spectra were obtained at 91 MHz. 

The first linkage between a microscope and an IR spectrophotometer was reported in 1949 [15]. Today, every manufacturer of IR spectrophotometers offers an optical/IR microscope sampling accessory. The use of optical and IR microscopy is a natural course of action for any solid state investigation. Optical microscopy provides significant information about a sample, such as its crystalline or amorphous nature, particle morphology, and size. Interfacing the microscope to an IR spectrophotometer ultimately provides unequivocal identification of one particular crystallite. Hence, we have the tremendous benefit of IR microscopy for the identification of particulate contamination in bulk or formulated drug products. 

In this IR sampling technique, a thermogravimetric (TG) analyzer is interfaced to an IR spectrophotometer so that the evolved gas from the sample/TG furnace is directed to an IR gas cell. This IR sampling technique lends itself to the identification and quantitation of residual solvent content for a pharmaceutical solid [17], and also to the investigation of pharmaceutical pseudopolymorphs. 

The infrared spectrum of griseofulvln, obtained as a mineral oil mull, was run on a Perkin-Elmer Model 180 grating IR spectrophotometer. Important absorption assignments are given in Table V. The spectrum is given in Figure 6. 

The infrared spectrum of pseudoephedrine hydrochloride is shown in Figure 1. It was obtained as a 0.2% dispersion of pseudoephedrine hydrochloride in KBr with a Nicolet Model 7199 FT-IR spectrophotometer.2 Table I gives the infrared assignments consistent with the structure of pseudoephedrine hydrochloride. 

Figure la. The optical arrangements of an FT-IR Spectrophotometer with reflectance attachments in the sample chamber for electrochemical experiments. (Reproduced with permission from Ref. 9. Copyright 1984 Elsevier.)... 

The double beam is particularly useful in qualitative analysis and most IR spectrophotometers operate on the double beam principle. A simplified double beam IR spectrophotometer has been given in the following figure with its essential units and functions. 

Most of the instruments, commonly used in an analytical laboratory, such as UV-Spectrophoto-meter, IR-Spectrophotometer, single—pan electric balance, pH-meter, turbidimeter and nephelometer, polarimeter, refractometer and the like must be calibrated duly, before use so as to eliminate any possible errors. In the same manner all apparatus, namely pipettes, burettes, volumetric flasks, thermometers, weights etc., must be calibrated duly, and the necessary corrections incorporated to the original measurements. 

The wavelength (or wave number) scale calibration of infrared spectrophotometers is usually carried out with the aid of a strip of polystyrene film fixed on a frame. It consists of several sharp absorption bands, the wavelengths of which are known accurately and precisely. Basically, all IR-spectrophotometers need to be calibrated periodically as per the specific instructions so as to ascertain their accuracy and precision. 

D,Z. Robinson AnalChem 24, 6l9(l952)(Qual Analysis with IR spectrophotometers)... 

FIGURE 3.4. Optical system of double-beam IR spectrophotometer. 

Infrared spectra may be obtained for gases, liquids, or solids. The spectra of gases or low-boiling liquids may be obtained by expansion of the sample into an evacuated cell. Gas cells are available in lengths of a few centimeters to 40 m. The sampling area of a standard IR spectrophotometer will not accommodate cells much longer than 10 cm long paths are achieved by multiple reflection optics. 

Spectral Measurements. The ir spectra were recorded on a Perkin-Elmer 621 grating ir spectrophotometer using KBr disks prepared from ir spectroquality powder (MCB) or 0.5 mm path length, NaCl solution ir cells. Electronic absorption spectra were recorded with a Cary 17 spectrophotometer using 1-cm quartz spectrophotometer cells. Mass spectra were recorded with an AE1 MS902 mass spectrometer. 

Figure 11.14—Optical path between the monochromator exit and the detector for two double beam instruments (rotating mirror model and semi-transparent mirror model). Instruments with rotating mirrors are similar to those used in IR spectrophotometers. However, the light beam from the source goes through the monochromator before it hits the sample. This minimises photolytic reactions that could occur if the sample is exposed to the total radiation from the source. The optics of instruments with two detectors are simpler and only one mirror, semi-transparent and fixed, is necessary to replace the delicate mechanisms of synchronised, rotating mirrors.

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