Recent advances in infra-red instrumentation

Abstract

The need of the chemist for a routine “bench” instrument has resulted in the development of low-cost, easy-to-operate, double-beam spectrophotometers. These also offer the opportunity of extending the teaching of infra-red methods and principles to a wider circle. Special filters and filtering techniques have allowed the incorporation of diffraction gratings in spectrometers without the use of a fore-prism. This has led to two important results: the development of simple monochromators of high performance and the ready extension of the wavelength range of infra-red measurements to 200 im. The prism-grating combination, however, is likely to be further developed as a routine wide-range instrument, especially in the measurement of band shapes and intensities, for the higher dispersion should minimize the effect of spectral slit width in these directions. It should also allow easier transfer of intensity data in quantitative analysis, although it is suggested that this problem would be eased, even with existing equipment, if a suitable intensity standard could be found. The application of scale expansion methods to trace analysis is described; the development of infra-red microspectroscopy and sampling techniques is also discussed.