The jet fuel formulation landscape is changing quickly. As the aviation industry accelerates its adoption of renewable sources such as plant matter and used cooking oil, analytical labs must evolve to maintain pace. Synthetic aviation turbine fuels (SATF) present new chemical complexities that demand more powerful testing methods. Comprehensive two-dimensional gas chromatography (GCxGC) provides the resolution needed to keep up, but the path to standardization has been anything but simple.
Scott Hoy, application chemist at Agilent, is highly familiar with these analytical hurdles—and he's determined to simplify GCxGC for routine laboratory use. Hoy, who joined Agilent in late 2021, recognized the importance of ASTM method D8396, the first standardized GCxGC method specifically developed for jet fuel.
Simplifying GCxGC for Real-World Labs
While traditional gas chromatography methods commonly analyze only 10–50 compounds in a sample, GCxGC can resolve between 1,000 and 2,000. That’s a massive leap in analytical power—but also complexity. "The large amount of data GCxGC produces can be challenging to analyze," Hoy explains. "This has been a significant hurdle for broader adoption outside of academic and major industrial R&D labs."
The challenges extend beyond data analysis. “Historically, GCxGC has operated using a technique called 'thermal modulation,' which produces very high-resolution data but requires a large tank of cryogen, for example, liquid nitrogen,” advises Hoy. “Some thermally modulated GCxGC systems also have issues with slight retention time movement after performing maintenance, such as changing the columns.” He also notes that many customers have never produced chromatographic data as dense as that produced by GCxGC, and the data analysis requires learning new software.
Hoy set out to address these pain points directly. Leveraging Agilent’s cryogen-free reverse flow modulator, he crafted a method that sidesteps traditional GCxGC complexities. "I aimed for a low-maintenance, robust solution that produced repeatable and reproducible data, and was easy to fix if the instrument went down," reveals Hoy. "Before Agilent, I spent several years as a quality control chemist managing a large fleet of GCs running many different methods. My goal was to create an analyzer that past-me would have been happy with."
A New Approach to Modulation
Hoy asserts that the combination of using high-temperature GC columns and operating the GCxGC instrument at relatively low temperatures significantly reduces the gradual shift of compound peaks over time. “Additionally, leveraging the Agilent Gas Clean filters on the GCxGC carrier gas prevented oxygen from entering the column, which greatly increases the column life. For laboratories analyzing jet fuel, adopting new technologies like GCxGC can be challenging, especially for users unfamiliar with these methods. Implementing a robust workflow is essential to easing the transition and reducing obstacles associated with introducing new technology.”
Central to Hoy's solution is Agilent’s reverse flow modulator, which dramatically reduced peak movement from run to run. "The retention time precision for all 42 compounds across 10 consecutive replicate analyses was exceptional, with several compounds having literally perfect precision (sigma = 0), which is not a term analytical chemists get to use very often,” remarks Hoy. This level of precision is particularly compelling—while tight alignment across 3 replicates might be dismissed as chance, achieving it over 10 runs significantly strengthens confidence in the result, much like flipping a coin and getting heads 10 times in a row would suggest more than just luck.
His collaborative efforts extended beyond his lab in Delaware as he worked closely with Agilent scientists in Shanghai. Together, they ensured compatibility with China’s emerging NB/SH/T 6078 standard, alongside ASTM D8396. "I showed the results to my colleague in Shanghai, who was working on NB/SH/T 6078, and she had just finished a similar precision study with her system and found the same incredible results,” Hoy enthuses.
Aware of the rising costs of helium, Hoy also developed a hydrogen-based carrier gas version of the method. What’s more, his approach can be easily adapted to other fuel types with minimal adjustments. “Even though ASTM D8396 is designed for jet fuel, my published method—developed in alignment with D8396’s performance-based criteria - can also analyze diesel simply by increasing the final oven temperature from 230 °C to 300 °C,” advises Hoy. “This approach works just as efficiently for synthetic and biodiesel blends.”
Hoy's method improves fuel analysis and supports the green transition, particularly for synthetic fuels. Its versatility increases accessibility and lowers entry barriers for a broader range of customers.
Discover the advantages of GC×GC and how it surpasses traditional GC in analysing complex samples.
A Turning Point for Both Scientist and Technique
For Hoy, contributing to this method marks a professional milestone. "I’ve long thought the first standardized GCxGC method from ASTM would open floodgates for proliferation of the technique outside of the research lab," Hoy reflects. "Being part of this process and developing Agilent's solution has brought me immense pride."
His contributions are also influencing ASTM directly. “Customers have been thrilled with the performance of the method,” remarks Hoy. “As part of the ASTM method stewardship process, the D8396 text is actively undergoing revisions with input from many ASTM members worldwide. These standardized methods are generally ‘performance-based,’ meaning users have flexibility in how they choose to implement the method, such as instrument make and model or column configuration, so long as the performance criteria in the standard are met.”
As for the future, Hoy sees potential for GCxGC to play a broader role in fuels production, particularly for hydrocarbon-based fuels and their synthetic or bio-based counterparts. “There are over 15 GC methods currently used to support the production of gasoline, jet, and diesel fuels. GCxGC could consolidate that to just two or three,” he explains. While GCxGC has been coupled with mass spectrometry since the 1990s, primarily in research, its potential for broader adoption remains strong. “Combining GCxGC with mass spectrometry reveals even deeper compositional information and continues to support innovation in next-generation fuels.”
