An analysis of coal liquids is demonstrated in the first application of the lifetime synchronous spectrum (LiSS) to the characterization of complex samples. The measurement of wavelength-resolved fluorescence life-times in the LiSS is shown to enhance the fingerprinting of coal liquids relative to conventional synchronous luminescence spectroscopy. The concentration independence of fluorescence lifetimes of individual compounds provides unique information about the composition of the coal liquids and the sources of their spectral features, indicating similarities among different samples and leading to the identification of regions in the synchronous spectra that are best for discriminating among the samples. The LiSSes also provided information about the nature of the processes responsible for spectral red shifts that occurred with increasing concentration of coal liquid.
Jeremy M. Shaver and Linda B. McGown, "Fluorescence Studies of Complex Coal Liquid Samples Using the Lifetime Synchronous Spectrum (LiSS)," Appl. Spectrosc. 49, 813-818 (1995)