Determination of jet fuel system icing inhibitor by GC×GC-FID.

Jet fuel usually contains a small amount of dissolved water, which can separate out at high altitudes and low temperatures. This can bring along serious clog issues as water can freeze in fuel pumps, lines, or filters; blocking the fuel flow which can even cause engine shut down. To prevent such a disaster, an additive called fuel system icing inhibitor (FSII) is added to jet fuels. The amount of FSII is regulated in both civil and military jet fuels by pertinent standards. A method for quantification of FSII: diethylene glycol monomethyl ether (DiEGME) by comprehensive two-dimensional gas chromatography with flame ionization detector (GC × GC-FID) was developed. The method allows the determination of DiEGME from a very small quantity of samples (0.5 µL) and is very fast with a mean absolute error of 0.001 vol% and a correlation coefficient of 0.9997. The DiEGME content (in the range of 0.07-0.12 vol%) in 23 fuel samples was analyzed via GC × GC-FID. The accuracy of the proposed method was evaluated by the ASTM standard D5006. The procedure that utilizes a refractometer, outlined in D5006, is currently the only available standard for determining the DiEGME concentration in fuel. Results were within the repeatability of the D5006 method (0.009 vol%). Since the D5006 method is accepted as an accurate technique for DiEGME content determination, the GC × GC method proposed in this study can be considered precise and accurate.

Identification and Quantitation of Linear Alkanes in Lubricant Base Oils by Using GC×GC/EI TOF Mass Spectrometry.

Linear alkanes are a class of compounds known to negatively affect the physical performance of lubricant base oils. The ability to rapidly identify and quantify linear alkanes in lubricant base oils would enable oil companies to more effectively evaluate their refinery methods for converting crude oil to lubricant base oils. While mass spectrometry is a powerful method for elucidation of the structures of compounds in complex mixtures, it is not innately quantitative. An approach is presented here for the identification and quantitation of linear alkanes in base oil samples by utilizing GC×GC/EI TOF MS. Identification of the linear alkanes in base oils was achieved based on their retention times in both GC columns as well as their EI mass spectra. Linear alkane model compound mixtures were used to generate calibration plots for quantitation of the linear alkanes in the base oils. The accuracy of this method was greater than 83.8%, within-day precision lower than 6.2%, between-day precision lower than 16.2%, and total precision lower than 17.2%. All noted figures of merit surpass the acceptable limits for a new validated quantitative method, where accuracy must be better than 80% and precision lower than 20% at the lower limit of quantitation. The n-alkane content in both base oil samples was further validated using a GC×GC/FID method (the gold standard for quantitation), which provided nearly identical results to those obtained using the GC×GC/EI TOF MS method. Therefore, GC×GC/EI TOF MS can be used to both identify and quantitate linear alkanes.

Middle distillates hydrogen content via GC×GC-FID.

Liquid transportation fuels in the middle distillate range contain thousands of hydrocarbons making the predictions and calculations of properties from composition a challenging process. We present a new approach of hydrogen content determination by comprehensive two-dimensional gas chromatography with flame ionization detector (GC×GC-FID) using a weighted average method. GC×GC-FID hydrogen determination precision was excellent (0.005 wt% repeatability). The method accuracy was evaluated by high-resolution nuclear magnetic resonance (NMR) technique, which is non-biased, measures the H signal directly and was independently validated by controls in the current study. The hydrogen content (in the range of 12.72-15.54 wt%) in 28 fuel samples were determined using GC×GC-FID. Results were within ±â€¯2% of those obtained via NMR. Owing to the fact that NMR is accepted as an accurate technique for hydrogen content determination, the GC×GC method proposed in this study can be considered precise and accurate.