Identification of Metabolites in Porcine Serum with Hydrogen Carrier Gas

Significance of the Topic

Metabolomics is a powerful tool for profiling small-molecule biomarkers in biofluids and tissues. Traditional GC/MS workflows rely on helium carrier gas, but global helium shortages and cost pressures have driven interest in hydrogen as an alternative. Demonstrating that existing metabolomics spectral libraries and workflows remain effective with hydrogen carrier gas is critical for laboratories seeking robust, cost-effective, and sustainable analyses.

Objectives and Study Overview

This study assessed the performance of a single-quadrupole GC/MS system running hydrogen carrier gas for metabolite identification using the Agilent Fiehn 2013 GC/MS Metabolomics RTL Library. Key goals included:

• Comparing retention times and library match scores for a standard fatty acid methyl ester (FAME) mix with helium versus hydrogen.
• Evaluating identification of the FAME mix spiked into porcine serum.
• Applying unknowns analysis to screen and identify endogenous serum metabolites at defined match factor thresholds.

Methodology and Instrumentation

A 1 µL split injection of derivatized standards and serum extras was performed on an Agilent 8890 GC with a Fast Oven and 5977C MSD equipped with the HydroInert source. A 10 m uncoated retention gap (0.18 mm ID) was connected to a 40 m × 0.18 mm DB-5ms column. Hydrogen carrier flow was set at 1.2 mL/min, inlet at 250 °C, transfer line at 290 °C, and mass scan range 50–600 m/z. Fatty acid and porcine serum samples were derivatized with MSTFA/1% TMCS and retention time-locked using a myristic acid d27 standard. A rich-text RI calibration file was created from FAMEs to support accurate retention index matching.

Main Results and Discussion

Retention time shifts between helium and hydrogen methods were minimal (≤0.06 min), and library match scores for FAME standards decreased by only 2–3%. In porcine serum spiked with the FAME mix, match factors ranged from 93.2% to 98.6%. Unknowns Analysis identified 76 endogenous metabolites at ≥90% match, 110 at ≥80%, and 143 at ≥70%. The incorporation of RI calibration was essential to prevent misidentification due to subtle retention time differences. Spectral comparisons confirmed that the HydroInert source preserves spectral fidelity when using hydrogen carrier gas.

Practical Benefits and Applications

• Helium replacement: Hydrogen provides a low-cost, abundant carrier gas alternative without sacrificing data quality.
• Library compatibility: Existing Fiehn RTL spectra acquired in helium remain valid for hydrogen-carrier analyses when using an RI calibration.
• Laboratory efficiency: Fritted inlet liners and quick-swap retention gaps reduce maintenance and column trimming.

Future Trends and Potential Applications

The successful use of hydrogen carrier gas suggests broader adoption in metabolomics and QA/QC laboratories. Future work may explore automated RI calibration workflows, expansion to tandem MS libraries, integration with high-throughput and clinical metabolomic platforms, and further optimization of hydrogen-compatible GC sources.

Conclusion

This study demonstrates that hydrogen carrier gas, together with the Agilent HydroInert source and retention index calibration, enables reliable metabolite identification using existing GC/MS metabolomics libraries. Adoption of this approach can mitigate helium supply challenges while maintaining high confidence in spectral matching.

Instrumentation Used

• Agilent 8890 GC with Fast Oven, split/splitless inlet
• Agilent 5977C single-quadrupole MSD with HydroInert source
• 10 m × 0.18 mm retention gap + 40 m × 0.18 mm, 0.18 µm DB-5ms column
• Autosampler syringe, fritted inlet liners, RI calibration files

References

1. Agilent Technologies. Agilent G1676AA Fiehn GC/MS Metabolomics RTL Library, Technical Overview; 2013.
2. Agilent Technologies. Metabolite Identification in Blood Plasma Using GC/MS and the Agilent Fiehn GC/MS Metabolomics RTL Library, Application Note 5990-3638EN; 2009.
3. Agilent Technologies. Agilent Inert Plus GC/MS System with HydroInert Source, Technical Overview 5994-4889EN; 2022.
4. Agilent Technologies. EI GC/MS Instrument Helium to Hydrogen Carrier Gas Conversion Guide 5994-2312EN; 2022.
5. Agilent Technologies. Agilent GC/MS Hydrogen Safety Manual G7006-90053; 2022.
6. Agilent Technologies. Hydrogen Safety for the Agilent 8890 GC System Guide 5994-5413EN; 2022.
7. Joseph S. et al. Impact of GC Liners on Lab Productivity with Complex Matrices, Application Note 5994-5546EN; 2022.
8. Haddad S. P., Quimby B. D., Andrianova A. A. GC/MS/MS Analysis of PAHs with Hydrogen Carrier Gas, Application Note 5994-5776EN; 2023.