Improvements to HILIC Robustness - a Targeted HILIC Metabolomics Method for Routine Analysis

Significance of the Topic

Polar metabolite profiling is essential for understanding cellular biochemistry, disease biomarkers, and metabolic pathways. Robust chromatographic separation of these polar compounds enables comprehensive coverage in both positive and negative ion modes, enhancing data reliability in routine metabolomics applications.

Objectives and Study Overview

This study aimed to develop and validate a highly reproducible, targeted HILIC metabolomics workflow for routine analysis of complex biological samples. Key goals included improving HILIC column robustness, expanding metabolome coverage, and enabling easy transfer of the method between laboratories.

Methodology and Instrumentation

• Sample preparation: Automated low‐volume plasma extraction using the Bravo Metabolomics Workbench coupled with Captiva EMR-Lipid solid‐phase extraction to remove proteins and lipids while enriching polar metabolites.
• Chromatography: Poroshell 120 HILIC-Z column (2.1 × 150 mm, 2.7 µm) operated on an Agilent 1290 Infinity II Bio LC system with MP35N metal alloy construction for improved peak shape and minimized metal interactions.
• Mobile phases: A – 20 mM ammonium acetate, pH 9.3 with 5 µM medronic acid in water; B – acetonitrile. Nonlinear gradient from 30 % to 98 % B over 16 min, total cycle time 24 min including re-equilibration.
• Mass spectrometry: Agilent 6495C triple quadrupole with ion funnel, employing dynamic and fixed dwell time MRM methods for over 400 targeted metabolites, with positive/negative polarity switching.

Main Results and Discussion

• Retention and Separation: The HILIC-Z column provided efficient retention of highly polar analytes (e.g., amino acids, TCA cycle intermediates) without ion pairing reagents, achieving baseline separation of isobaric compounds like leucine/isoleucine.
• Reproducibility: Retention time RSDs remained below 5 % across multiple column lots, operators, days, and laboratories, demonstrating robust method transferability.
• Sensitivity: Limits of quantitation in pooled bovine plasma were in the low femtomole range (e.g., 20 fmol for 15N5-ADP with 10 % RSD; 1.2 fmol for 13C-phenylalanine with 1 % RSD), supporting quantitative applications.
• Coverage: Over 200 endogenous metabolites were consistently detected in a single injection, spanning amino acids, nucleotides, coenzymes, glycolytic and TCA cycle intermediates.

Benefits and Practical Applications

The proposed workflow streamlines targeted metabolomics for high‐throughput labs, offering:

• Comprehensive profiling of polar metabolites in one method with dual‐mode ESI.
• Automated low‐volume sample prep that reduces manual intervention and variability.
• Scalable protocol easily adopted across different sites to support large‐scale studies.

Future Trends and Potential Applications

Building on this robust HILIC approach, future directions include expanding the targeted panel to cover additional pathways, integrating isotopic tracing for flux analysis, and applying the workflow to diverse matrices such as tissues and microbial extracts. Further optimization of MS acquisition strategies may enhance throughput and sensitivity.

Conclusion

A standardized HILIC-Z metabolomics method has been established, combining automated low‐volume extraction, robust chromatography, and extensive MRM acquisition. The workflow delivers sensitive, reproducible quantitation of hundreds of polar metabolites and can be readily transferred between laboratories to accelerate biological research.

References

• Sartain M, Gomez M, Van de Bittner G, Shu H. Enabling Automated, Low‐Volume Plasma Metabolite Extraction with the Agilent Bravo Platform. Agilent Application Note 5994-2156EN.