抄録
Liquid scintillation counting (LSC) fails to determine biofuel contents in gasoline containing red fuel dyes (In Japan and USA, gasoline is dyed in red). In this study, the determination of biofuel contents in blue-dyed gasoline was compared with that in red-dyed gasoline on the assumption that the color quenching of a blue dye was lower than that of a red dye. To simulate gasoline containing biofuels, bioethanol or ethyl tert-butyl ether (ETBE) was mixed with n-hexane at a concentration of 25%. Solvent Red 26 and Solvent Blue 35 were added to the "simulated gasoline" at concentrations of 40 - 400 ppm, and ^<14>C was measured for 500 min using Tri-Carb 3180 TR/SL (PerkinElmer). The biofuel contents were precisely determined for the both colors when the concentration of fuel dyes was 40 ppm. When the concentration of fuel dye reached 400 ppm, the simulated gasoline containing Solvent Red 26 provided wrong results for determining biofuel contents. In contrast, Solvent Blue 35 had much smaller effects on the quantitative determination. The counting efficiencies were affected by the fuel dyes in a similar manner for the determination of biofuel contents. Absorbance spectra of the fuel dyes indicated that Solvent Red 26 absorbed fluorescence from the first and second solutes (i.e. fluorescent substances). On the other hand, Solvent Blue 35 had no absorbance in λmax of the second solutes. These results suggest that a blue dye enables us to determine biofuel contents in gasoline by direct measurements of LSC.
