No. 6 fuel oil measured at 80 and 20 K are compared in Figure 5. The major differences are increases in the intensities of the bands at 720 and 725 cm-1 at the lower temperature. These changes provide additional data for identifying petroleum; however, we do not feel that a couple of additional data values warrant the time and effort it takes to measure spectra at 20 K. Thus, we are confining our analyses to liquid N2 temperature.Results from this study indicate that low temperature infrared spectrometry can be used subsequent to room temperature infrared analysis for identifying petroleum products and petroleum pollution sources. The low temperature technique is only slightly more time consuming than room temperature analysis. Collaborating data from other analytical techniques will undoubtedly be needed in court cases; however, in spills where several similar oils are involved, infrared spectra measured at room temperature followed by measurements at 80 K provide convincing evidence for identifying the source. ACKNOWLEDGMENTWe express our appreciation to D. Eastwood for suggesting this study, and to A.
The ultraviolet absorption spectra, fluorescence and phosphorescence excitation and emission spectra of sixteen barbiturates and certain model compounds have been examined and correlated. The structure of the fluorescent dianion in the 5,5-disubstituted barbiturates was shown. Phosphorescence was observed at a lower wavelength than that of the prompt fluorescence at room temperature for those barbiturates containing a 5-phenyl substituent. The fluorescence derived from the dianionic form of the heterocyclic ring, whereas the phosphorescence derived from the aromatic nucleus. The effects of steric interactions and pH on the phosphorescence of the phenyl substituted barbiturates are discussed. Detection limits at room temperature and at 77 K for the barbiturates in common use have been determined.
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