Application of Novel HILIC Column Configurations to Improve LC/ESI/MS Sensitivity of Metabolites

Importance of the Topic

Hydrophilic interaction chromatography (HILIC) addresses the critical need for sensitive analysis of polar metabolites in complex biological and environmental samples.

By employing organic-rich mobile phases and water as the strong eluent, HILIC enhances electrospray ionization efficiency and reduces background noise, making it indispensable for metabolomics, pharmaceutical research, and quality control applications.

Objectives and Study Overview

This work evaluates novel HILIC column configurations on superficially porous particles and PEEK-lined hardware to maximize LC/ESI/MS sensitivity for isobaric and polar analytes.

The study systematically compares sensitivity gains over reversed-phase LC (RPLC) using:

• Different particle sizes (5 μm, 3.5 μm, 1.8 μm) on C18 columns
• Three Agilent InfinityLab Poroshell 120 HILIC phases (zwitterionic, poly-hydroxy fructan, OH5)
• PEEK-lined stainless steel columns in an inert LC system

Methodology and Instrumentation

Analyses were performed on a UHPLC system coupled to a triple quadrupole mass spectrometer in electrospray mode. Key instrumentation includes:

• Agilent 1290 Infinity LC System with bio-inert configuration
• Agilent 6410A Triple Quadrupole LC/MS
• Agilent InfinityLab Poroshell 120 HILIC columns (2.1×100 mm, 2.7 μm superficially porous)
• PEEK-lined stainless steel column hardware and PEEK/SST capillaries

Mobile phases consisted of aqueous ammonium formate buffers (pH 3.0–6.8 or high-pH mixtures) and acetonitrile blends, with gradient and isocratic elution tailored for target analytes.

Main Results and Discussion

1. Particle Size and Phase Effects

• Transitioning from 5 μm to 1.8 μm C18 columns increased sensitivity up to five-fold for morphine glucuronides.
• Replacing C18 with HILIC-Z columns yielded four-fold signal-to-noise improvements due to taller peaks and lower noise.

2. Isobar Resolution

• Zwitterionic and poly-hydroxy phases resolved isobaric amino acid pairs and morphine metabolites, aiding unambiguous quantitation.

3. High-pH Stability and Ruggedness

• InfinityLab Poroshell 120 HILIC-Z maintained performance at pH up to 12 and 80 °C, extending column lifetime.
• PEEK-lined hardware minimized metal interactions, boosting signal for sticky and buffer-rich samples.

Benefits and Practical Applications

The combined approach delivers:

• Enhanced LC/ESI/MS sensitivity for low-abundance polar metabolites.
• Orthogonal selectivity for complex mixture profiling and isobar discrimination.
• Robust performance under harsh solvent or pH conditions, reducing downtime and column replacement.

Applications span metabolomics, drug metabolite screening, bioanalysis of nucleotide phosphates, and QA/QC in pharmaceutical and food industries.

Future Trends and Potential Uses

Advances in HILIC stationary phases and inert flow paths are expected to:

• Enable deeper coverage of polar metabolomes in clinical and environmental studies.
• Integrate with high-resolution MS for comprehensive structure elucidation.
• Support high-throughput workflows with automated method development using orthogonal HILIC chemistries.

Emerging materials may further improve selectivity, peak capacity, and tolerance to biofluid matrices.

Conclusion

Novel HILIC column configurations on superficially porous particles, combined with PEEK-lined hardware and bio-inert LC systems, substantially improve LC/ESI/MS sensitivity and selectivity for polar and isobaric analytes.

This integrated solution offers robust, high-throughput analysis for diverse metabolite applications and sets the stage for continued expansion of HILIC in advanced analytical workflows.

Reference

• Agilent Application Note 5991-8922EN, Chromatographic Resolution of Morphine Glucuronides
• Agilent Application Note 5991-0245EN, High pH Stability with InfinityLab Poroshell 120 HILIC-Z