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

Importance of the Topic

Comprehensive compositional profiling of complex refinery streams such as (bio)diesel and jet fuels is essential for product quality, regulatory compliance and performance optimization. Group‐type analysis (PiPNA) classifies hydrocarbons into paraffins, naphthenes and aromatics to guide refining processes, monitor blending consistency and detect adulteration in routine laboratories.

Objectives and Study Overview

This application note presents a dedicated flow‐modulated GC×GC–FID method optimized for PiPNA of diesel and jet fuels, including fatty acid methyl esters (FAMEs). The goals were to eliminate cryogenic modulation, enhance robustness, achieve high resolution across mid‐boiling components (up to 450 °C final boiling point) and validate quantification accuracy and repeatability against established reference methods.

Methodology and Instrumentation

The system employs a non-cryogenic flow modulator interfaced with two capillary columns: a polar stationary phase in the first dimension for chemical class separation, and a non-polar phase in the second for isomer resolution. Key parameters such as column length, phase chemistry, carrier gas flows and oven temperature programming were fine-tuned to sharpen peaks and maximize peak capacity. Quantification uses theoretical FID response factors normalized for precise weight‐percent results.

• Flow-modulated GC×GC modulator (no liquid CO₂ or N₂ required)
• First-dimension polar column, second-dimension non-polar column
• Flame ionization detector with theoretical response factors
• Oven program optimized for boiling range up to 450 °C

Main Results and Discussion

The optimized method successfully resolved and quantified n-paraffins, iso-paraffins, cycloparaffins, mono- and polyaromatics, and FAMEs in a gravimetric QC mixture. Recoveries ranged from 94 % to 103 % with overall totals near 100 %. Repeatability (n = 10) showed relative standard deviations below 1.3 % across chemical groups. Comparison to EN 12916 HPLC–RID for total aromatic content in two round-robin samples yielded slightly lower GC×GC values but remained within method reproducibility.

• Gravimetric standard recoveries: 96–102 %
• Repeatability RSD: 0.08–1.23 % by group
• Agreement with EN 12916: within reproducibility limits
• Enhanced resolution in C20–C24 region and clear FAME detection

Benefits and Practical Applications

The flow-modulated GC×GC–FID approach offers:

• High‐throughput, robust analysis without cryogenic complexity
• Enhanced separation for detailed group‐type profiling
• Routine laboratory compatibility with minimal maintenance
• Simultaneous PiPNA and FAME quantification in diesel and jet fuel

Future Trends and Possibilities

Anticipated advancements include coupling flow modulation GC×GC with mass spectrometry for compound‐specific identification, automated data processing workflows for real-time monitoring, expanded application to next-generation biofuels and trace impurity profiling, and integration into process control for refinery optimization.

Conclusion

AC Analytical Controls’ dedicated flow-modulated GC×GC–FID analyzer delivers reliable, high-resolution PiPNA and FAME analysis of (bio)diesel and jet fuels. By eliminating cryogenics and optimizing modulation parameters, the method achieves excellent accuracy, precision and robustness suitable for both research and routine quality control environments.