Single compounds may be identified using luminescence spectroscopy, eg. by fluorescence or phosphorescence measurements, since the exciting and emission wavelengths differ (giving essentially zero background) and are specific to the compound. Total luminescence spectroscopy makes possible the analysis of simple mixtures. It involves the measurement of intensity over the useful range of exciting and emission wavelengths. Results are presented as intensity contours with the exciting and emission wavelengths as coordinates; the components of a mixture can then be identified. -- AATA