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The analysis of aromatic compounds in jet fuel is commonly achieved by the analysis methods according to ASTM D1319 (Fluorescence Indicator Absorption) and ASTM D6379 (HPLC-Refractive Index Detection). Since June 2019 the new method ASTM D8267 can be reported, meanwhile added to the specification standard ASTM D1655.
The method consists of gaschromatographic separation in combination with VacuumUltraviolet detection in the wavelength range between 125 – 240 nm. This approach provides an innovative analytical technique enabling several different areas of application. High energetic short-wave UV light induces an electron transfer in almost all chemical bonds to an excited state σ → σ* or π → π* respectively. The absorption of UV is detected and allows to record characteristic spectra. By this approach it is possible to assign single compounds to certain classes.
The following figure depicts the schematic design of the analytical system and principle of detection.
The schematic depiction of the VUVdetector consists of a Deuterium lamp, flow-cell, and detector module. Depending on the chemical bonds, absorption takes place at different wavelengths and produces characteristic spectra. On basis of the detected spectra, single compounds can be identified and assigned to different classes and quantified according to Beer-Lambert-Law.
The quantification of mono- and di-aromatic compounds in jet fuel is only one application of this technique.
The absorption of saturated compounds (125 – 160 nm) has been plotted in red, the absorption of aromatic compounds (170 – 200 nm) has been plotted in green. An assignment to mono- and di-aromatics is achieved based on the characteristic absorptions. By application of specific response factors, it is possible to calculate directly proportional the amounts in mass and volume percentage, respectively.
Using GC-VUV we can also offer a PIONA analysis (ASTM D8071) and a VHA analysis (WK 64297: verified hydrocarbon analysis see DHA). In addition, there will also be an analysis of diesel fuel in the future!