With regard to hazardous chemicals, a 1979 Coast Guard report lists approximately 90 substances that can be readily identified by their room-temperature fluorescence spectra. Eastwood and Lidberg indicated that this list could be extended to about 250 hazardous materials if low-temperature luminescence/phosphorescence spectra were included.
Figure 9 shows a spectral comparison of PCB samples acquired at 77 K, where the emission intensity is greater for phosphorescence than fluorescence. Low-temperature analysis is considerably more sensitive, allowing quantification in the ppb range. For field-screening in the ppm range, room-temperature fluorescence appears satisfactory, for fluorescence quenching by the internal heavy-atom effect is incomplete.
In the future, Eastwood and Lidberg intend to use their SPEX system to expand the library of spectral references for petroleum oils and hazardous chemicals. The exceptional sensitivity of their FLUOROLOG system also will be applied to developing a more comprehensive system of classifying spectra: one that would encompass subclasses based on spectral characterization rather than just API categories or physical properties. Information about the geographical origin of oils could also be integrated into such a framework.
In addition, preliminary PCB measurements need to be expanded and refined to ensure better detection, identification, and quantification for these ubiquitous chemicals, especially in field work. The same holds true for other important classes of fluorescin