An HPLC-ESI-QTOF method to analyze polar heteroatomic species in aviation turbine fuel via hydrophilic interaction chromatography.

Aviation turbine fuel is a complex mixture of thousands of compounds. An analytical method using hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray ionization and quadrupole time-of-flight mass spectrometry (ESI-QTOF) was developed for the identification of heteroatomic, polar compounds in aviation turbine fuel. Although compounds containing oxygen, nitrogen, and sulfur functional groups are each found at low levels (<0.1 % by mass) in fuels, their presence can generate significant effects on fuel properties. The HILIC-ESI-QTOF method is a combined separation and detection technique that possesses many advantages including a fast and simple sample preparation-requiring no extraction step therefore ensuring no loss of compounds of interest-and the ability to acquire high-fidelity compound data for chemometric analysis of heteroatomic species in aviation turbine fuel. In the development of the method, it was found that the chromatographic conditions and nature of the injection sample had a significant effect on separation efficiency and repeatability. For a sample dataset optimized using a singular aviation turbine fuel, retention time shift was able to be reduced from 0.4 min to 2.0 % relative standard deviation (RSD) to approximately 0.1 min with RSD of 0.4 % using the newly developed method. In addition, a high number of untargeted molecular features (944) and targeted amines (121) were able to be identified when utilizing optimal method conditions. The specific benefits and limitations of utilizing HILIC techniques with HPLC-ESI-QTOF are also discussed herein. This new method is currently being expanded to include analysis of all heteroatoms and is being applied to real fuel sets. The results of these studies are forthcoming.

Quantification of elemental and total carbon in combustion particulate matter using thermal-oxidative analysis.

The use of a two-step thermal-oxidative analysis (TOA) technique for quantification of the mass of total carbon (TC) and elemental carbon (EC) of turbine engine-borne particulate matter (PM) has been evaluated. This approach could be used in lieu of analysis methods which were developed to characterize diluted PM. This effort is of particular interest as turbine engine PM emissions typically have a higher EC content than ambient aerosols, and filter sample mass loadings can be significantly greater than recommended for existing analysis techniques. Analyses were performed under a pure oxygen environment using a two-step temperature profile; reference carbon and actual PM samples were used to identify appropriate analysis conditions. Thermal gravimetric analysis (TGA) methods were used to provide guidance on the nature of the carbon in several of the materials. This was necessary as a standard reference material does not exist for determination of the EC fraction in PM. The TGA also assisted in identifying an appropriate temperature range for the first-stage of the TOA method. Quantification of TC and EC for turbine engine PM samples using TOA was compared to results obtained using the NIOSH 5040 thermal-optical method. For first-stage TOA temperatures of 350°C and 400°C, excellent agreement between the techniques was observed in both the quantified TC and EC, supporting the viability for using TOA for analysis of turbine engine PM samples. A primary benefit of using TOA for these types of PM samples is that filters with relatively high PM mass loadings (sampled at the emission source) can be readily analyzed. In addition, an entire filter sample can be evaluated, as compared to the use of a filter punch sample for the NIOSH technique. While the feasibility of using a TOA method for engine PM samples has been demonstrated, future studies to estimate potential OC charring and oxidation of EC-type material may provide additional data to assess its impact on the OC/EC fractions for other carbon-type measurements. Implications: This work presents results and procedures of an analytical method for the determination of total and elemental carbon, i.e., TC and EC present in combustion source particulate matter samples. In general, it is shown that the LECO TOA methodology is as reliable and comprehensive as NIOSH 5040 for determining TC and EC carbon types in particulate matter present in turbine emission sources, and should be considered as an alternative. Principles of the methodology, differences, and corresponding agreement with the standard NIOSH 5040 method and TGA analysis are discussed.