Spectroscopic Techniques and Chromatography

Abstract

Chromatography is primarily a separation technique, the observed detector response being a record of the quantity of solute molecules eluted from the chromatographic system. Although procedures have been developed for identifying separated components in a mixture, for example the two column GC method (see Experiment 21, Chapter 9), and a system of reference indices has been collated, they are limited either to a specific application or to a group of compounds. Identification of the component or components in an eluted band (peak) is only possible if we can ascertain that one type of molecule alone is present and can obtain sufficient unique information on the structure and physical properties of the compound. The latter may be achieved by obtaining spectroscopic data on the eluted molecules; if a peak is sampled several times during elution then the number of components contained in the peak can be established. In order to obtain the spectral data the spectrometer must be capable of performing a scan very rapidly and certainly several times during the elution time for the first peak of a chromatogram. Developments in microelectronics, instrument design and microcomputers have enabled mass spectrometers, infrared and UV-visible spectrophotometers and atomic absorption instruments to be successfully used as chromatography detectors.