Infrared Spectrophotometers

Willey R R 1976 Fourier transform infrared spectrophotometer for transmittance and diffuse reflectance measurements Appl. Spectrosc. 30 593-601... 

Two common detectors, which also are independent instruments, are Fourier transform infrared spectrophotometers (FT-IR) and mass spectrometers (MS). In GC-FT-IR, effluent from the column flows through an optical cell constructed... 

Figure 3.23 A typical double-beam recording mid-infrared and near-infrared spectrophotometer...

The goal of the basic infrared experiment is to determine changes in the intensity of a beam of infrared radiation as a function of wavelength or frequency (2.5-50 im or 4000—200 cm respectively) after it interacts with the sample. The centerpiece of most equipment configurations is the infrared spectrophotometer. Its function is to disperse the light from a broadband infrared source and to measure its intensity at each frequency. The ratio of the intensity before and after the light interacts with the sample is determined. The plot of this ratio versus frequency is the infrared spectrum. 

Traditional infrared spectrophotometers were constructed with mono-chromation being carried out using sodium chloride or potassium bromide prisms, but these had the disadvantage that the prisms are hygroscopic and the middle-infrared region normally necessitated the use of two different prisms in order to obtain adequate dispersion over the whole range. 

Fig. 19.2 Layout of an infrared spectrophotometer employing a diffraction grating for monochromation. Reproduced by permission from R. C. J. Osland, Principles and Practices of Infrared Spectroscopy, 2nd edn, Philips Ltd, 1985.

All infrared spectrophotometers are provided with chart recorders which will present the complete infrared spectrum on a single continuous sheet, usually with wavelength and wavenumber scales shown for the abscissa and with absorbance and percentage transmittance as the ordinates. More advanced instruments also possess visual display units on which the spectra can be displayed as they are recorded and on which they can be compared with earlier spectra previously obtained or with spectra drawn from an extensive library held in a computer memory. These modern developments have all led to quantitative infrared spectrophotometry being a much more viable and useful analytical procedure than it was just a few years ago. 

Tests. Chem analysis consists of reaction with KI soln and titration of the liberated I with Na thiosulfate soln. Instrumental analysis consists of measurement of the carbonyl absorption at 1760cm 1 using an infrared spectrophotometer. This procedure is valid for any physical state or soln strength of the acid (Ref 10)... 

F.C. Strong III, How the Fourier transform infrared spectrophotometer works. J. Chem. Educ., 56(1979) 681-684. 

Characterization. Infrared Spectroscopic Analysis - The infrared spectra of all the chemically modified polybutadienes were obtained using a P.E. 1330 Infrared Spectrophotometer. The samples were prepared by casting polymer films on NaCl plates. 

The infrared absorption spectrum of miconazole nitrate was obtained in a KBr pellet using a Perkin-Elmer infrared spectrophotometer. The IR spectrum is shown in Fig. 4, where the principal peaks were observed at 3140, 3070, 2995, 2920, 1566, 1525, 1445, 1385, 1310, 1070, and 710 cm-1. Assignments for the major infrared absorption band are provided in Table 2. Clarke reported principal peaks at 1085, 1319, 827, 1302, 1038, and 812 cm-1 (miconazole nitrate, KBr disc) [2]. 

The infrared absorption spectrum of niclosamide is shown in Fig. 4. It was obtained in a KBr disc using a Unicam SP200 infrared spectrophotometer. The principal peaks were noted at 1210, 1340, 1410, 1530, 1565, 1645, 3030, and 3270 cm-1. 

The infrared absorption spectrum of (/))-penicillamine was obtained using a Perkin-Elmer infrared spectrophotometer. The spectrum shown in Fig. 2 was obtained with... 

Products in the reaction mixture were analyzed by infrared and nmr spectroscopy. IR spectra were obtained on a Perkin-Elmer 521 infrared spectrophotometer. The reaction mixture was first suction filtered through a fine porosity glass frit inside a glove box (Vacuum Atmosphere HE-43-2) under an argon atmosphere, and was placed in NaCl cells (International Crystals, Inc.) of path length 0.1 or 0.5 cm with Teflon stoppers. H nmr spectra... 

In this paper we will first describe a fast-response infrared reactor system which is capable of operating at high temperatures and pressures. We will discuss the reactor cell, the feed system which allows concentration step changes or cycling, and the modifications necessary for converting a commercial infrared spectrophotometer to a high-speed instrument. This modified infrared spectroscopic reactor system was then used to study the dynamics of CO adsorption and desorption over a Pt-alumina catalyst at 723 K (450°C). The measured step responses were analyzed using a transient model which accounts for the kinetics of CO adsorption and desorption, extra- and intrapellet diffusion resistances, surface accumulation of CO, and the dynamics of the infrared cell. Finally, we will briefly discuss some of the transient response (i.e., step and cycled) characteristics of the catalyst under reaction conditions (i.e.,... 

E. J. Shinouskis built the infrared reactor cell and conducted the infrared reactor experiments. The authors are indebted to J. A. Sell for the modifications of the infrared spectrophotometer, and to Professor A. T. Bell for sharing his experience with infrared reactor construction. The CO conversion data of Figure 3 were obtained by J. E. Carpenter. 

The infrared spectrum of bromocriptine mesilate in a KBr pellet is given in fig. 1. It was recorded on a Perkin Elmer 257 infrared spectrophotometer. 

The infrared spectrum of calcitriol is shown in Figure 1 (1). The spectrum was recorded on a Perkin-Elmer Model 283 Grating Infrared Spectrophotometer and was measured in a KBr pellet which contained 1 mg of calcitriol in 300 mg of KBr. 

The infrared spectrum of nalidixic acid in a KBr pellet is presented in Figure 3. The spectrum was obtained on a Perkin-Elmer Infrared Spectrophotometer Model 21. It agrees with the spectrum presented by Salim and Shupe.(2)... 

PGDN was generated from a sample of Otto Fuel II by blowing air across a Pyrex reservoir of the compound to the return air duct of the air conditioner. Eighty percent of the air was recirculated. The concentration of PGDN in the air was monitored continuously by an infrared spectrophotometer and by a gas chromatograph fitted with an electron capture detector. The vaporized Otto Fuel II was 99% pure PGDN as measured by infrared analysis. 

Table 1.1 Visible-ultraviolet-near infrared spectrophotometers... 

Lambda 2 Ultraviolet-visible double-beam spectrophotometer Lambda 3 Ultraviolet-visible double-beam spectrophotometer Lambda 5 and Lambda 7 Ultraviolet visible spectrophotometers Lambda 9 Ultraviolet visible—near infrared spectrophotometer Lambda Array 3430 Spectrophotometer... 

The infrared spectrophotometers are based on either single monochromation or double monochromation ... 

The schematic layout of a single-monochromator infrared spectrophotometer has been duly depicted in Figure 22.2. 

Figure 22.2. Optical Diagram of a Single-Monochromator Infrared Spectrophotometer.

The schematic optical diagram of a double-beam infrared spectrophotometer has been shown in Figure 22.3 as per Beckman Model IR-9. 

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