Unlocking Robust, Reproducible Separations for Modern Peptide Therapeutics with BioResolve™ Peptide Phenyl Hexyl+ Columns

Significance of the topic

The increasing structural complexity of modern peptide therapeutics — exemplified by GLP-1 receptor agonists and dual-/multi-agonists with noncanonical residues and hydrophobic conjugates — places growing demands on chromatographic methods for impurity profiling. Robust, selective, and reproducible separations are essential for confident detection and quantitation of closely related sequence variants, isomeric impurities, and conjugation-related species in development, QC, and stability testing environments.

Objectives and study overview

This application note evaluates the analytical performance of the BioResolve Peptide Phenyl‑Hexyl+ column (1.6 µm, 230 Å superficially porous charged-surface particles) for impurity profiling of clinically relevant peptide drugs. The study focused on: batch-to-batch and column-to-column reproducibility, column-related sample carryover, and operational robustness over a sustained injection sequence (500 injections). A representative peptide mixture (insulin, an insulin deamidation impurity, semaglutide, liraglutide, tirzepatide, and cagrilintide) was used to challenge the column selectivity and stability.

Instrumentation

The evaluation used standard high-throughput UPLC hardware and UV detection configured as follows:

• System: ACQUITY Premier UPLC System with Binary Solvent Manager (BSM), Flow‑Through Needle Sample Manager (FTN), and CH‑A Column Heater
• Detector: ACQUITY UPLC TUV detector, analytical flow cell (10 mm, 500 nL), detection at 214 nm
• Column: BioResolve Peptide Phenyl‑Hexyl+ (1.6 µm, 230 Å, superficially porous charged‑surface particle)
• Column temperature: 55 °C; sample temperature: 5 °C; injection volume: 5 µL
• Mobile phases: A = 0.1% formic acid in water; B = 0.1% formic acid in acetonitrile

Methodology

The test mixture delivered approximately 0.9 µg total peptide per injection (each peptide at ~0.18 µg, insulin degradant at ~8% relative abundance). Reproducibility was assessed across four independent batches of packing material and across columns built from the same stationary phase batch but different hardware lots. Carryover experiments used two full gradient cycles following the primary elution (without reinjection) to isolate column-related retention. Column lifetime testing consisted of 500 consecutive injections under the described low‑pH gradient conditions with monitoring of retention, resolution, peak shape, and backpressure.

Key results and discussion

Batch-to-batch and column-to-column reproducibility

• Inter-batch retention time variability: ≤0.5% RSD for all peptide peaks; average peak area RSD ≈5%.
• Intra-batch (different hardware lots) retention time variability: ≤0.2% RSD; peak area RSD ~5% and USP half-height resolution for the critical insulin/degradant pair <4% RSD.
• These low RSD values indicate uniform stationary phase production and consistent column manufacturing, minimizing analytical drift due to hardware or material variability.

Carryover performance

• Column-related carryover was negligible: average total carryover <0.04% on the first post-run elution and <0.01% on the second.
• Observed residual signal originated primarily from the most strongly retained peptides (semaglutide, liraglutide, tirzepatide), consistent with expected retention behavior for hydrophobic, conjugated peptides.
• Blank elution baselines confirmed minimal lingering analyte signal, supporting reliable low‑level impurity detection in sequence runs.

Operational robustness / column lifetime

• After 500 continuous injections: relative retention shifts ≤1% for all analytes versus the reference injection.
• Resolution between insulin and its deamidation impurity changed by about 5% (USP half‑height resolution), indicating maintained selectivity.
• Peak shape metrics (USP tailing factor and peak width at half height) changed on average ~4% across peaks.
• Backpressure increased by ~215 psi (~15% increase) at 0.2 mL/min, demonstrating acceptable physical stability under prolonged low‑pH operation.

Taken together, the results demonstrate that the phenyl‑hexyl selectivity combined with charged surface chemistry and a 230 Å pore design provides enhanced mass transfer and complementary retention mechanisms suitable for structurally complex and higher‑molecular‑weight peptides. The surface charge likely contributes to improved peak shape and reproducibility under the acidic conditions typical for peptide LC and LC–MS workflows.

Benefits and practical applications

The evaluated column offers multiple practical advantages for peptide therapeutic analysis:

• High reproducibility supports reliable batch release testing and comparative impurity profiling across production lots.
• Minimal carryover reduces the risk of false positives or inflated impurity estimates in sequence runs, improving data confidence in trace-level analyses.
• Robust performance over hundreds of injections supports high-throughput environments and routine QC laboratories.
• Phenyl‑hexyl selectivity and charged-surface characteristics provide improved separation of hydrophobic conjugates and closely related sequence variants compared with some conventional reversed-phase phases.

These characteristics make the column especially suitable for GLP-1 receptor agonists, dual-agonists, amylin analogs, and other modified peptide modalities requiring high-resolution impurity profiling.

Future trends and opportunities

Looking forward, analytical demands for peptide therapeutics will continue to evolve as molecules incorporate larger payloads, novel linkers, and expanded chemical modifications. Key opportunities include:

• Further optimization of stationary-phase chemistries to separate stereoisomeric and isobaric peptide impurities (e.g., D‑amino acid isomers).
• Integration with high-resolution MS workflows to combine the column’s selectivity with structural identification of low‑level degradants.
• Development of standardized robustness protocols that simulate longer-term QC use and matrix complexity (formulations, excipients).
• Application of superficially porous, charged‑surface particles to native or intact peptide/protein analysis where pore accessibility and mass transfer are limiting factors.

Conclusion

The BioResolve Peptide Phenyl‑Hexyl+ column delivers reproducible retention, low carryover, and stable chromatographic performance under acidic UPLC conditions for a range of clinically relevant peptide therapeutics. Its combination of phenyl‑hexyl selectivity, charged surface, and large-pore superficially porous particles supports high‑confidence impurity profiling, especially where conventional reversed‑phase columns may lack the necessary selectivity or mass-transfer characteristics.

References

1. Peri RV, Anchan H, Jonnalagadda K, Varghese R, Gupta P. Designing GLP‑1 Delivery: Structural perspectives and Formulation Approaches for Optimized Therapy. Nutrition & Diabetes. 2025;15:53.
2. Zhang B, Xu W, Yin C, Tang Y. Characterization of Low‑Level D‑Amino Acid Isomeric Impurities of Semaglutide Using Liquid Chromatography–High Resolution Tandem Mass Spectrometry. Journal of Pharmaceutical and Biomedical Analysis. 2023;224:115164.
3. Manetto S, et al. Comparing the Performance of Electrostatic Repulsion–Reversed Phase Chromatography Approaches in the Resolution of Complex Peptide Mixture: liraglutide as case study. European Journal of Pharmaceutical Sciences. 2025;211:107120.
4. Hanna CM, Koza SM, Shiner S. Characterization and Impurity Profiling of Combined Amylin and GLP‑1 Analogs with RapiZyme Trypsin. Waters Application Note. 720008925. June 2025.