TABLE OF CONTENTS The time has long since passed when one could rely on gas chromatographic data alone to identify unknown compounds in gas chromatograms. The sheer number of compounds that could be present would invalidate reliance on the use of such techniques. The practice nowadays is to link a mass spectrometer (or NMR or FT-IR spectrometers, see following sections) to the outlet of the GC so that a mass spectrum is obtained for each chromatographic peak as it emerges from the separation column. If the peak contains a simple substance then computerised library searching facilities attached to the MS will rapidly identify the substance. If the emerging peak contains several substances, then the mass spectrum will provide information on the substances present. Alternatively, different gas chromatographic columns can be tried that will resolve the mixture of substances in question.
The use of GC-MS grew rapidly during the early 1970s as discussed by Shackleford and McGuire [105].
There are now several suppliers of equipment for carrying out this technique (see Appendix 1). One supplier is Finnigan MAT, which supplies single-stage quadruple mass spectrometers.
This offers premium single-stage performance, with the option of being upgraded to a triple-stage quadrupole system (i.e., the TSQ70). The SSQ70 features a network of distributed microprocessors with more than 1.5 megabytes of memory linked to a powerful DEC 11/73 processor with 2.0 megabytes of memory for data-processing operations. Instrument control tasks can be displayed in...
