LOW INTENSITY SPECTRAL-ANALYSIS (LISA) OF COAL MACERALS AND THE ASSESSMENT OF DGC FRACTIONS

Low intensity spectral analysis (LISA) represents an extension of fluorescence analysis that enables the study of all maceral groups. This is made possible by replacing the standard double grating monochromator and photomultiplier assembly, used in conventional fluorescence, with a fixed grating, image intensifier and diode array. This detection equipment can be used to measure extemely low intensity signals extending below the visual threshold. The increased sensitivity is achieved by using the capability of the diode array to accumulate a signal over an extended period of time. Techniques have been developed that exploit the signal gathering ability of this equipment enabling fluorescence spectral acquisition from 500 to 850 nm on all coal macerals including fusinite. The sensitivity of this analysis system permits high resolution spectral analysis into the near i.r. The capability of measuring "non-fluorescing" macerals permits the evaluation of maceral fractions obtained from density gradient centrifugation runs. The density interval over which single maceral concentrations are obtained can be rapidly determined using low intensity fluorescence analysis.