Analysis of mono- and di-aromatics in Jetfuel
by GC-VUV according to ASTM D8267
Up to now the analytical methods ASTM D1319 (Fluorescence Absorption) and ASTM D6379 (HPLC-Refractive Index Detection) were available for the quantification of the aromatic content in Jet Fuel. Since June 2019 the new method ASTM D8267 is available and now also added to the specification standard ASTM D1655.
Gaschromatography according to ASTM D8267
This method consists of a gaschromatographic separation in combination with Vacuum-Ultraviolet-Detection at a wavelength range between 125 – 240 nm (Vacuum-UV) and provides an innovative analytical technique for different applications. Highy energy short-wave UV-light induces electron transitions in excited states σσ* or ππ* in almost all chemical bonds and provides the possibility to record characteristic spectra. By this approach it is possible to assign compounds to different chemical classes.
The principle of the detection is depicted in the following figure.
The VUV-Detector consists of a Deuterium lamp, Flowcell and Photo-Detector. Depending on the chemical bonding, absorption takes place at different wavelengths and by this produces characteristic spectra, which are used for an explicit assignment to chemical compound classes and quantification according to the Lambert-Beer law.
The quantification of mono- and diaromatic contents in Jet Fuel is only one application of this technique.
The absorption of saturates at 125 – 160 nm is displayed in red, the absorption of aromatic compounds at 170 – 200 nm is displayed in green. The assignment of mono- and diaromatic compounds is based on their characteristic absorption ranges. Specific response factors are applied and by this detected absorptions can be converted directly proportional into mass and volume percent, respectively.
GC-VUV can also be applied for a PIONA analysis (ASTM D8071) and VHA analysis (WK 64297: verified hydrocarbon analysis comparable to DHA). Furthermore, there will be an analysis method for diesel fuel in due course!