Researchers from Monash University in Clayton, Australia created a new 3D-printed device for gas chromatography (GC) procedures, demonstrating its ability to conduct multidimensional and enantioselective separation. Their findings were published in the Journal of Chromatography A (1).
GC has been a mainstay in chemical analysis for decades, being effective for analyzing mixtures of volatile compounds. However, it may have shortcomings with providing sufficient resolution to resolve multi-component mixtures. Researchers have tried overcoming the resolution deficiency in various ways, such as multi-dimensional gas chromatography (MDGC) and comprehensive two-dimensional gas chromatography (GC x GC), which requires a modulation device for implementation. Thermal modulators were the earliest types used, which continue to be popular to this day.
In this study, the scientists created a device 3D printed using stainless steel intended for operation as a cold trapping assembly when cooled by liquid CO2, in a manner similar to a longitudinally modulated cryogenic system (LMCS). There is precedent for using cryogenic systems in chromatography, with the ability to remobilize trapped components allowing for various new methods to be used during chromatographic analysis (2). Further, when implanted alongside GC, analysts can start using powerful separation technology.
The cold trap enclosure design was detailed, with the system’s performance being tested to assess its suitability for use as a collection and rapid re-mobilization device for GC analysis of volatile organic compounds (VOCs). The precision of modulation period timing was evaluated, showing a maximum error of 8 µs and average variation of < 1 ns across 10000 successive modulations. Using an alkane series (C5-C9), the system’s trapping capabilities were tested. It was found that the system successfully trapped analytes and producing peaks with full width at half height (FWHH) as low as 65 ms.
Maximum trapping time was assessed for hexane, with the modulator retaining the compound for up to 9 s in a 100 °C oven before breakthroughs were observed. The modulator was then applied to investigate enantioselective separation of limonene, a type of oil extracted from the peels of citrus fruits (3). While a single chiral column was used, various lengths (20 cm–5.0 m) of column were drawn through the modulator, with the lengths effectively functioning as enantioselective second dimension (2D) columns. Injected (R,S)-limonene enantiomers were collected as a single entity, then rapidly released to the 2D column. The 3D modulator was found to trap hexane sufficiently to allow modulation periods of up to 8 s; this was demonstrated with oven temperatures of up to 100 ºC, and while higher temperatures were not tested, the researchers do believe hexane modulation above this point is possible.
Overall, comprehensive two-dimensional GC was demonstrated to be viable using 3D-printed modulators for a tea tree oil sample. While the 2D retention time exceeded what was required for conducting effective GC x GC using these lengths, the scientists believe the separation can be further improved on by adjusting column and method parameters.
(1) Wittman, I. A.; Jarvis, T.; Hearn, M. T. W.; Marriott, P. J. A 3D printed Cryogenic Device for Gas Chromatography: Design, and Performance Demonstrated for Multidimensional and Enantioselective Separations. J. Chromatogr. A 2025, 1754, 466017. DOI:
(2) Marriott, P.; Kinghorn, R. Cryogenic Solute Manipulation in Gas Chromatography – The Longitudinal Modulation Approach. TrAC - Trends Analyt. Chem. 1999, 18 (2), 114–125. DOI:
(3) Sobel, A. What Is Limonene? Everything You Need to Know. Healthline 2023.
