Overcoming nonspecific binding in liquid chromatography: enhancing assay sensitivity, accuracy, and reproducibility in peptide/protein workflows

Importance of Nonspecific Binding in LC–MS Workflows

As biotherapeutic analyses reach ever-lower concentration regimes, losses due to nonspecific binding (NSB) can undermine sensitivity, accuracy and reproducibility. Understanding and mitigating NSB—protein or peptide adhesion to vials, needles and tubing—ensures robust quantitation critical for drug discovery, QA/QC and regulatory compliance.

Study Objectives and Experimental Design

This work evaluated five key factors influencing NSB in a reversed‐phase LC–MS assay for four proteins (insulin, glucagon, semaglutide, NISTmAb):

• Vial fill volume (1/3 vs. 2/3 of volume)
• Storage time in autosampler (6, 12, 24 h)
• Autosampler temperature (5 °C vs. 25 °C)
• Organic modifier content in diluent (0% vs. 20% ACN)
• Vial material (unmodified glass, silanized glass, polypropylene)

Design of experiments was applied to test combinations of these variables to quantify recovery effects at trace and reference concentrations.

Methodology and Used Instrumentation

Sample preparation involved dilution of stock into 0.1% formic acid in water with or without 20% acetonitrile. Analysis used a Thermo Scientific Vanquish Horizon LC system coupled to UV detection on:

• Hypersil GOLD C18 column (100 × 2.1 mm, 1.9 µm) for peptides
• MAbPac RP Phenyl column (100 × 2.1 mm, 4 µm) for NISTmAb

Chromatographic gradients and flow rates were optimized per analyte; data were acquired and processed in Chromeleon CDS 7.3.2.

Main Findings and Discussion

• Organic modifier: Addition of 20% ACN dramatically improved recovery for insulin, glucagon and semaglutide, achieving up to 100% recovery; NISTmAb was largely unaffected.
• Autosampler temperature: Elevated temperature (25 °C) increased recovery of glucagon across all vial types and slightly improved insulin recovery in unmodified glass but reduced it in silanized glass; semaglutide showed minor effects; NISTmAb was insensitive.
• Vial storage time: Insulin and semaglutide exhibited decreased recovery over 24 h in glass vials; glucagon and NISTmAb adsorption kinetics appeared rapid and stable.
• Vial fill volume: No statistically significant effect on protein recoveries was observed.
• Vial material: Hydrophobic surfaces (silanized glass, polypropylene) increased NSB without organic modifier, especially for insulin and glucagon; glass choice and surface treatment influenced adsorption profiles.

Practical Implications

Implementing a controlled level of organic organic solvent in sample diluent is the most effective strategy to suppress NSB for small proteins and peptides. Temperature and vial surface chemistry should be matched to analyte stability and adsorption propensity. Laboratories can achieve consistent recoveries and method robustness by:

• Standardizing diluent composition (e.g., 20% ACN)
• Validating temperature settings against heat‐labile samples
• Selecting vial materials based on analyte hydrophobicity

Future Trends and Applications

Further research could expand to additional vial coatings, explore silane chemistries and evaluate NSB under ultra‐trace workflows such as native MS. Integration of microfluidic sample handling and automation may reduce surface exposure and improve throughput while maintaining recovery.

Conclusion

Nonspecific binding poses a variable risk across peptides and proteins. Organic modifier in diluent emerged as the primary control factor. Secondary influences—temperature, vial surface and storage time—must be assessed in method validation. A systematic DOE approach enables laboratories to optimize LC–MS workflows for maximal sensitivity and reproducibility.

References

1. Maes K. et al. Strategies to reduce aspecific adsorption of peptides and proteins in LC–MS bioanalyses. J. Chromatogr. A. 2014;1358:1–13.
2. Jung MC. Achieving maximum protein and peptide recovery using QuanRecovery vials. Waters white paper. 2019.
3. Mathes J. Protein adsorption to vial surfaces: quantification, structural and mechanistic studies. Cuvillier Verlag. 2010.