Adsorption Phenomenon and Development of Low Adsorption Vials for LC and LC/MS

Importance of the Topic

High-sensitivity liquid chromatography–mass spectrometry (LC/MS) is a cornerstone technique across pharmaceuticals, environmental monitoring, and proteomics. As analyte concentrations decline toward trace levels, adsorption losses to sample vials can introduce significant bias and reduce reproducibility. Developing low-adsorption containers is therefore critical to ensure data reliability and maintain detection limits at the femtomole to attomole scale.

Objectives and Overview of the Study

The study aimed to characterize adsorption mechanisms in conventional glass and polypropylene (PP) vials and to develop two innovative vial types—LabTotal glass vials and TORAST-HTM Bio PP vials—with minimized sample losses. Using basic small molecules and trypsin-digested peptides as models, adsorption behaviors were quantified and compared across container types.

Methodology and Instrumentation

Sample adsorption was evaluated by injecting 1 mg/L solutions of four basic compounds (amitriptyline, atenolol, imipramine, propranolol) and trypsin-digested myoglobin/BSA into LC/MS. Recovery rates were determined from chromatographic peak areas. Surface morphology of vials was analyzed by scanning probe microscopy (SPM), including atomic force microscopy (AFM) and laser scanning microscopy (LSM). Instrumentation included a high-sensitivity Shimadzu LC/MS system for quantitative analysis and SPM platforms for topographical characterization.

Main Results and Discussion

• Ionic adsorption of high-pKa basic compounds to silanol groups on glass surfaces and hydrophobic adsorption (driven by logP) to both glass and PP were confirmed.
• Addition of salts suppressed ionic binding, while organic solvents or surfactants inhibited hydrophobic interactions, but sample preparation complexity increased.
• LabTotal glass vials featured optimized molding parameters to minimize surface roughness and contact area, yielding 85–100% recovery for basic analytes versus 37–97% in commercial vials.
• TORAST-HTM Bio PP vials were coated with a non-ionic superhydrophilic polymer to block hydrophobic peptide binding, achieving near-quantitative recovery of tryptic peptides compared with significant losses in uncoated glass and PP.
• Surface images confirmed smoother LabTotal interiors (AFM/LSM height variation <1 µm) and uniform hydrophilic coatings on TORAST-HTM Bio vials.

Benefits and Practical Applications

• Enhanced reproducibility and accuracy in trace-level LC/MS quantitation for pharmaceutical drug monitoring, biomarker discovery, and environmental analysis.
• Simplified sample preparation by reducing the need for additional additives that can interfere with chromatographic separation or ionization.
• Compatibility with existing LC/MS workflows without hardware modifications.

Future Trends and Potential Uses

• Extension of low-adsorption coatings to other container materials (e.g., PEEK, PTFE).
• Integration with automated liquid handling systems for high-throughput workflows.
• Development of tailored surface chemistries to address adsorption of diverse analyte classes including lipids and nucleic acids.

Conclusion

The newly developed LabTotal glass and TORAST-HTM Bio PP vials significantly mitigate ionic and hydrophobic adsorption of small molecules and peptides, respectively. Their adoption in high-sensitivity LC/MS analyses can improve data integrity, lower detection limits, and streamline sample preparation.

References

• Murakoshi M, Fukuzawa K, Sato Y, Asakawa N. Adsorption Phenomenon and Development of Low Adsorption Vials for LC and LC/MS. Shimadzu GLC Ltd & Shimadzu Corporation.