Why Use HILIC and HIC Chromatography?

Significance of the Topic

The effective separation of polar small molecules and intact proteins is a critical challenge in analytical chemistry laboratories dealing with metabolites, glycans, peptides and biologics. Standard reversed phase chromatography often fails to retain highly polar and ionized species, while protein therapeutics can denature under harsh organic conditions. Hydrophilic interaction liquid chromatography (HILIC) and hydrophobic interaction chromatography (HIC) offer complementary selectivity and milder operating conditions that enhance retention, resolution and compatibility with mass spectrometry, facilitating both small-molecule and biotherapeutic analysis.

Objectives and Overview of the Study

This work presents theory and practical guidance for developing robust HILIC and HIC methods. Key goals include understanding retention mechanisms, selecting appropriate columns and mobile phases, optimizing method parameters for common application areas such as glycan profiling and monoclonal antibody critical quality attribute analysis, and providing best practices for column care, sample handling and detection to ensure reproducibility across diverse laboratory environments.

Methodology and Instrumentation

Method development strategies were demonstrated using a range of Agilent hardware and consumables under varying mobile phase and gradient conditions. Instrumentation included:

• Agilent 1260 Infinity II bio-inert liquid chromatography system
• Agilent 6490 triple quadrupole LC/MS for metabolite and vitamin analysis
• Agilent Ultivo LC/TQ system with electrospray ionization
• Diode array detector and fluorescence detector for UV-active and derivatized analytes
• InfinityLab Poroshell 120 HILIC, HILIC-Z and AdvanceBio Amide columns for glycan separation
• AdvanceBio HIC columns with wide pore bonded phase for protein and antibody separation

Mobile phase components included high-organic acetonitrile mixtures buffered with volatile ammonium formate or acetate for HILIC, and high salt solutions of ammonium sulfate or tartrate with phosphate buffers for HIC, using gradient elution to modulate retention.

Main Results and Discussion

HILIC retention was shown to increase with organic content and polar analyte ionization, enabling separation of amino acids, isobaric compounds and water-soluble vitamins that elude reversed phase methods. Column equilibration time was reduced by increasing aqueous content and using PEEK-lined columns minimized metal interactions to improve sensitivity in MS detection. Deactivator additives further suppressed unwanted metal binding. In HIC mode, proteins and antibody variants were separated under native conditions using high salt to promote hydrophobic adsorption followed by salt gradients for elution. AdvanceBio HIC columns delivered high resolution, batch-to-batch reproducibility and faster throughput even at reduced salt concentrations, facilitating critical quality attribute monitoring of monoclonal antibodies, oxidation variants and drug-conjugated species. Two-dimensional LC combining HIC with reversed phase desalting enabled MS identification of intact and fragmented antibody species.

Benefits and Practical Applications

HILIC extends retention and selectivity for polar small molecules in metabolomic, glycomic and pharmaceutical QC workflows without major hardware changes. It is fully compatible with MS detection and provides alternative selectivity to reversed phase. HIC preserves protein tertiary structure and enables detailed analysis of therapeutics, including oxidation, deamidation, isomerization and drug-antibody ratio profiling. The methods are readily transferable to QC labs, offering robust performance, rapid column equilibration, minimal carryover and scalable throughput for routine CQA monitoring.

Future Trends and Potential Applications

Ongoing developments include new stationary phase chemistries with enhanced pH and thermal stability, lower salt requirements for HIC, integrated bioinert flow paths to maximize MS sensitivity, and automated method scouting software for accelerated optimization. Coupling HILIC or HIC with multidimensional separations, online desalting and high-resolution mass spectrometry will drive deeper characterization of complex biomolecules and post-translational modifications. Advances in column technology, machine learning assisted method design and miniaturized UHPLC systems promise further gains in speed, resolution and sensitivity.

Conclusion

HILIC and HIC chromatography provide powerful, complementary tools for analyzing polar small molecules and intact proteins under conditions that preserve analyte integrity and maximize detection sensitivity. By understanding retention mechanisms, selecting appropriate columns and mobile phases, and following best practices for sample preparation and column care, laboratories can achieve high-resolution separations, robust reproducibility and seamless integration with MS workflows. These methods expand the capability of analytical chemists to tackle challenging applications in metabolomics, glycomics and biopharmaceutical quality control.