Identification and quantification of trace oxygenated compounds in alternative jet fuels: Fluorescence methods for fast detection of phenolic compounds in operational field conditions

Abstract The trace-oxygenated compounds in jet fuel reduce thermal stability. The identification and quantification of oxygenated species is typically conducted using solid phase extraction (SPE) followed by the analysis of extracted molecules by GC–MS. Our experimental results confirmed that SPE followed by methanol extraction of phenolic compounds could separate and recover quantitatively the oxygenated polar species from the fuel; however, the method is labor-intensive. The UV-Fluorescence of methanol-soluble SPE phenol doped jet fuels showed a linear response with phenol concentration. Although in general the UV-fluorescence response of phenols in jet fuel is linear, differences in response were observed depending on the type of standard studied. The differences in response can be explained by the nature of side functional groups in phenol with quenching effects. Fluorescence quenching with Rhodamine B (Rh-B) was explored for the direct analysis of phenols in jet fuels. The strong binding ability of phenols on Rh-B explain the quenching effect observed. However, studies conducted with other jet fuels indicates that nature of the fuel matrix also influences Rhodamine B (Rh-B) UV quenching. To address this issue, a new method that removes oxygenated compounds by SPE and that compares the Rhodamine-B spectra before and after SPE was developed.