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46 May / June 2021


Group-Type Analysis in Jet Fuel and Diesel by Flow Modulated GCxGC-FID


Jop Bezuijen*, Product Manager - Chromatography, Rob Strik, Application Specialist PAC LP, Rotterdam Netherlands


Corresponding Author * Jop.Bezuijen@paclp.com Introduction


The development of two-dimensional gas chromatography introduced the possibility to provide reliable compositional information on middle distillate refinery streams such as jet fuel and diesel. The original GCxGC systems mainly relied on cryogenic modulation, which is effective but has some analytical challenges and downsides for routine laboratory use. The most common are:


• High cost of ownership due to the large consumption of liquid CO2 or liquid Nitrogen. • Requires a lot of lab space.


• Cryogenic modulation is maintenance intensive. • Low boiling point components are hard to trap and may break through the cryogenic trap.


The challenge that flow modulation presents method developers is in optimising application parameters such as column length, column phase, column flows and GC oven programming to achieve the desired separations. However, once the right parameters have been determined, flow modulation rewards the operator with a lower cost, lower maintenance, and easier to use GC x GC application which also eliminates low boiler breakthrough issues common to the cryogenic trap.


AC Analytical Controls BV (AC) (Netherlands) has solved this analytical challenge and has developed a ready to use flow modulated GC x GC application that provides a complete group-type analysis of jet fuel and diesel fuel streams, including biodiesels blends such as B5, B7 and B10. In addition to the commonly required paraffin (P), naphthene (N) and aromatic (A) species and group results, additional information about the speciated and total Fatty Acid Methyl Esters (FAME) content is reported for biodiesel blends.


This article describes the basic configuration for this AC GC x GC application, and provides information regarding group-type separation and the used quantification method. In addition, we describe how the quantitation results of the application are validated for jet fuel and diesel samples by comparing the values found using the GC x GC method with existing CEN methods for the determination of Total Aromatics and Total FAME content in the applicable products.


Experimental Instrument configuration


The flow modulated AC group-type in jet fuel and diesel GCxGC application uses reversed phase chromatography, a polar column as the 1st dimension column and a non-polar column as the 2nd dimension column. This modulation method and column setup yields sharper, better defined peaks and thus better peak resolution, as demonstrated in Figure 1.


The flow modulation setup (Figure 2) was further optimised for the application by tuning column lengths, column phase, column coating, column flows and GC oven programming. These system parameters are all critical in obtaining proper modulation, and since the modulator is the heart of every GCxGC system they are vital for getting proper results.


Figure 1. Examples of Standard Flow Modulation (top chromatogram) and AC Flow Modulation (bottom chromatogram of Cyclohexane


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