Infrared spectrophotometry instrumentation

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. 

Chemical Testing. Adequate instrumentation for a variety of different test methods should be available. Most stability-indicating chemical assays are performed by high-performance liquid chromatography. Occasionally, gas chromatography, infrared spectrophotometry, or spectrofluorimetry are used. Test... 

The United States Pharmacopoeia (U.S.P.) [5] in a chapter on validation of compendial methods, defines analytical performance parameters (accuracy, precision, specificity, limit of detection, limit of quantitation, linearity and range, ruggedness, and robustness) that are to be used for validating analytical methods. A proposed United States Pharmacopeia (U.S.P.) general chapter on near-infrared spectrophotometry [6] addresses the suitability of instrumentation for use in a particular method through a discussion of operational qualifications and performance verifications. 

Total hydrocarbons in the air may be determined using infrared spectrophotometry. The hydrocarbons are collected in a condensation trap immersed in liquid oxygen. The hydrocarbons absorb in the 3- to A-jxnx region of the infrared spectrum using a 20-m pathlength cell. They are expressed as parts per million hexane, and the instrument is calibrated using a hexane standard. 

Infrared spectrophotometry is a familiar established analytical technique which provides identification of compounds by fingerprint spectra, of which a vast library is available. Both liquid and gaseous samples may be easily analysed and therefore modifications of established sample handling techniques have enabled both GC and HPLC instruments to be readily interfaced. Ideally, scan times of less than 1 s are required to be able to record each peak and peak shoulders. Instrument sensitivity is sufficient so that on the fly recording of spectra can be obtained from GC and HPLC eluants which contain nanograms of sample per ml mobile phase, for example, 10 ng sample in 100 pi GC-IR sample cell. Fourier transform infrared (FTIR) instruments are able to meet these criteria but until recently the instrumentation and computer system have been too expensive for routine use. The new generation of... 

It is becoming more and more desirable for the analytical chemist to move away from the laboratory and into the field via in-field instruments and remote, point of use, measurements. As a result, process analytical chemistry has imdeigone an offensive thmst in regard to problem solving capabiUty (77—79). In situ analysis enables the study of key process parameters for the purpose of definition and subsequent optimization. On-line analysis capabiUty has already been extended to gc, Ic, ms, and ftir techniques as well as to icp-emission spectroscopy, flow injection analysis, and near infrared spectrophotometry (80). 

Goddu, R.F. Near infrared spectrophotometry. In Advances in Analytical Chemistry and Instrumentation Reilly, C.N., Ed. John Wiley and Sons, Inc. New York, 1960 Vol. 1. 

Ultraviolet spectrophotometry n. A method of chemical analysis similar to infrared spectrophotometry, except that the spectrum is obtained with ultraviolet light. It is somewhat less sensitive than the IR method for polymer analysis, but is useful for identifying and measuring plasticizers and anti-oxidants. An example of a UV spectrum of pyridine is shown. Willard HH, Merritt LL, Dean JA (1974) Instrumental methods of analysis. D. Van Nostrand Co., New York. 

Near-infrared spectrophotometry did not become feasible for the ordinary laboratory until the lead sulfide photoconductive cell had been installed in commercial instruments. This did not occur until the early fifties. Near-infrared workers are still entitled to feel like pioneers. 

The references given in this bibliography are, principally, to the theoretical considerations, principles, methodology, and instrumentation of infrared spectrophotometry and Raman spectra. References to specific applications are included wherein new techniques are given or the application may be of general interest. Numerous references to bibliographies giving specific applications are to be found in this compilation. 

R. F. Goddu, Near-Infrared Spectrophotometry, in Advances in Analytical Chemistry and Instrumentation, Vol. I, edited by C. N. Reilley, Interscience Publishers, Inc., New York, 1960. 

In modern times, most analyses are performed on an analytical instrument for, e.g., gas chromatography (GC), high-performance liquid chromatography (HPLC), ultra-violet/visible (UV) or infrared (IR) spectrophotometry, atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry. Each of these instruments has a limitation on the amount of an analyte that they can detect. This limitation can be expressed as the IDL, which may be defined as the smallest amount of an analyte that can be reliably detected or differentiated from the background on an instrument. 

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