HPLC-Charged Aerosol Detection eBook

Significance of the Topic

Reliable analysis of pharmaceutical excipients is critical for ensuring drug safety, efficacy and consistent product quality. Many excipients lack UV chromophores or consist of complex mixtures, making traditional HPLC-UV methods inadequate. Charged aerosol detection (CAD) coupled with UHPLC enables universal, structure-independent detection and quantitation of non-volatile compounds, improving impurity profiling and formulation development.

Objectives and Overview

The whitepaper reviews methods for high-performance liquid chromatography (HPLC) with charged aerosol detection in the qualitative and quantitative analysis of excipients—including adjuvants, amino acids, carbohydrates, counterions, surfactants, polyethylene glycols and protein stabilizers. Key goals are to present universal detection principles, demonstrate uniform response characteristics and illustrate workflows for excipient profiling in both R&D and QA/QC laboratories.

Methodology and Instrumentation

• Working principles of CAD:

• Nebulization of column effluent into aerosol droplets.
• Drying to form particles, charged via corona discharge.
• Measurement of total particle charge by a sensitive electrometer, yielding a response proportional to analyte mass.

• UHPLC-CAD platforms:

• Thermo Scientific Vanquish Charged Aerosol Detector.
• Thermo Scientific Corona Veo Charged Aerosol Detector.

• Column chemistries:

• Fully porous C18/C30 phases (Hypersil GOLD, Acclaim) for broad compound coverage.
• Superficially porous “core-shell” (Accucore) phases for UHPLC sensitivity.
• Polar embedded and mixed-mode (Accucore Polar, Acclaim Trinity P1/P2) for ionizable and hydrophilic analytes.
• Hydrophilic interaction (HILIC) for simple sugars and amino acids.
• Reverse-phase C4/C8 for peptides, proteins and lipid-like excipients.

Main Results and Discussion

• Universal detection of non-volatile excipients from small organic acids to large PEGs and proteins, overcoming UV invisibility.
• Uniform mass-based response (<5% RSD) across diverse compound classes using a single calibrant.
• Examples:

• Adjuvant mixtures (saponins, phosphatidylcholines, squalene emulsions) profiled by UHPLC-CAD with dedicated gradients.
• Underivatized amino acids separated by HILIC-CAD in sub-5-minute runs.
• Simple sugars and cyclodextrins resolved by HILIC or PA2 reversed phase columns.
• Simultaneous detection of APIs and counterions (e.g., metformin-chloride, penicillin-KCl) on mixed-mode columns.
• Polysorbate-80 characterization: fatty acid impurity profiling and lot-to-lot variability assessment.
• 2D heart-cut methods coupling RPLC for protein with HILIC-CAD for amino acid excipients in biologics.

Benefits and Practical Applications

• Comprehensive excipient and impurity profiling without derivatization or multiple detectors.
• Single-calibrant quantitation simplifies method development and reduces reliance on reference standards.
• High sensitivity (sub-nanogram) and wide dynamic range suitable for trace impurity and major component analysis.
• Robust performance for active pharmaceutical ingredients, biologics, food ingredients and specialty chemicals.

Future Trends and Opportunities

• Integration with MS and automated sample preparation to expand structural elucidation capabilities.
• Miniaturized, micro-flow CAD interfaces for even higher sensitivity in early-stage drug discovery.
• Artificial-intelligence-driven method optimization for rapid excipient screening.
• Extension of CAD to novel polymeric excipients and complex biologic-drug combinations.

Conclusion

Charged aerosol detection paired with UHPLC provides a universal, sensitive and reproducible solution for the analysis of pharmaceutical excipients and related impurities. Its ability to detect all non-volatile compounds with uniform mass response streamlines method development and enhances quality control across the drug development lifecycle.

Used Instrumentation

• Thermo Scientific Vanquish UHPLC system with Charged Aerosol Detector
• Thermo Scientific Corona Veo Charged Aerosol Detector
• Hypersil GOLD, Accucore and Acclaim series columns (C18, C30, Polar, Trinity P1/P2, PA2, HILIC)
• Standard UHPLC accessories: Bioinert flow paths, precision pumps and thermostatted column ovens

References

• Thermo Scientific. Excipients Applications Notebook. AN71104; 2019.
• Thermo Scientific. Direct Analysis of Multicomponent Adjuvants by HPLC-CAD. PO70333; 2016.
• Gamache P.H., Ed. Charged Aerosol Detection for Liquid Chromatography and Related Separation Techniques. Wiley; 2017.
• Schilling K., Pawellek R., Holzgrabe U. Influence of CAD Instrument Settings on Polysorbate 80 Fatty Acid Analysis. J. Chromatogr. A 2018, 1576, 58–66.