Operational Principle of MicroJet Cryo Trap (MJT-1030E)

Significance of the topic

Analysis of trace gaseous species and volatiles is crucial for various fields such as polymer analysis, environmental monitoring, and quality control. Efficient trapping and focused desorption of analytes at the head of a gas chromatographic column improve detection limits and peak shapes, enabling accurate quantitation of dilute compounds.

Objectives and study overview

The technical note presents the operational principle of the MicroJet Cryo Trap (MJT-1030E), designed to trap trace components in gases or volatiles desorbed from heated samples over a broad boiling point range. It describes how the system cools the column head to sub-ambient temperatures using a micro jet of liquid nitrogen and subsequently achieves rapid thermal desorption for high-resolution gas chromatographic analysis.

Methodology and instrumentation

The MJT-1030E uses a two-stage process:

• Cooling: Liquid nitrogen is liquefied in a thermal exchange coil immersed in a LN2 reservoir and delivered through a transfer tube to a micro jet tube surrounding the GC column head. A temperature sensor monitors the column temperature, which can be lowered to –180 °C or below by directing a fine jet of liquid nitrogen onto the column.
• Thermal desorption: After trapping, the liquid nitrogen flow is stopped and the GC oven heats the column section at a ramp rate of up to 800 °C per minute, releasing the analytes in a narrow band for subsequent separation.

Used Instrumentation

• MicroJet Cryo Trap MJT-1030E (Frontier Laboratories Ltd.)
• Gas chromatograph oven configured to accommodate the micro jet assembly
• Liquid nitrogen supply system with thermal exchange coil and flow controller

Main results and discussion

The MJT-1030E demonstrates effective trapping of volatile and semi-volatile analytes over a wide boiling point range by achieving rapid (sub-second) cooling to cryogenic temperatures. The subsequent rapid heating cycle ensures narrow desorption bands, enhancing chromatographic resolution and sensitivity. The design prevents moisture freezing by allowing evaporated nitrogen to purge both ends of the micro jet tube.

Benefits and practical applications

• Significantly improved detection limits for trace gases and volatiles
• Enhanced peak sharpness and reproducibility in GC analyses
• Versatility for polymer analysis, environmental monitoring, and QA/QC applications
• Minimized sample carryover and moisture interference due to self-purging design

Future trends and potential applications

Advancements may include integration with automated sampling systems, coupling with mass spectrometry for enhanced compound identification, and development of miniaturized cryo-trapping modules for field-portable GC instruments. Novel cryogens or closed-loop cooling circuits could further improve safety and sustainability.

Conclusion

The MicroJet Cryo Trap MJT-1030E provides a robust solution for cryogenic focusing of trace analytes in gas chromatographic workflows. Its fast cooling and heating cycles improve analytical performance across diverse applications.

Reference

Hosaka et al., 3rd Polymer Analysis Symposium, I-6, pp. 15–16 (1998).