Fast and accurate absolute quantification of antibodies and antibody-drug conjugates using Isotope Dilution-Triple Quadrupole ICP-MS

Accurate quantification of proteins remains a key challenge in life sciences, as traditional methods such as colorimetry, amino acid analysis, UV‑Vis spectroscopy or ELISA often require specific standards, involve complex preparation steps, or suffer from limited precision and matrix interferences.

Inductively Coupled Plasma Mass Spectrometry (ICP‑MS), combined with isotope dilution mass spectrometry (IDMS), offers a generic alternative by enabling elemental detection that is largely independent of molecular structure.

The development of triple quadrupole ICP‑MS (ICP‑QQQ) significantly improves the removal of spectral interferences, enabling reliable sulphur quantification, a key element present in most proteins.

This approach allows absolute quantification of antibodies and antibody‑drug conjugates (ADCs) without the need for compound‑specific calibration standards.
The complete methodology and results are detailed in the full application note available for download.

KEY HIGHLIGHTS OF THE METHOD

• Absolute quantification using isotope dilution ICP‑QQQ without the need for protein reference standards
• Excellent accuracy with < 2% bias and recoveries close to 100%
• High precision with RSD typically below 1% (down to 0.13–0.35% in validation)
• Strong linearity demonstrated (R = 0.99998) across tested ranges
• Fast workflow with results obtained within half a day in routine use

HOW THIS SUPPORTS YOUR ANALYTICAL PROGRAMME?

The ID‑ICP‑QQQ approach provides a robust and versatile solution for protein quantification, overcoming the limitations of conventional assays and simplifying analytical development

• Eliminates the need for compound‑specific standards, simplifying method setup
• Ensures reliable results through effective removal of spectral interferences
• Delivers consistent performance across different matrices and formulation buffers
• Enables absolute quantification of proteins, antibodies and ADCs using a single methodology
• Supports accurate determination of sulphur content, critical for protein quantification
• Integrates with complementary MS techniques for ADC characterisation (e.g. DAR determination)

This method contributes to more robust, reproducible and efficient analytical strategies in biotherapeutic development.

USE CASES

• Quantification of monoclonal antibodies
• Analysis of ADCs
• Determination of sulphur content in proteins and peptides
• Measurement of drug‑to‑antibody ratio (DAR) in combination with mass spectrometry
• Analysis of sulphur‑containing biomolecules in various matrices