Monitoring of On-column Methionine Oxidation as Part of a System Suitability Test During UHPLC-MS/MS Peptide Mapping.

Peptide mapping by liquid chromatography-tandem mass spectrometry (LC-MS/MS) is an essential analytical tool for the characterization of biotherapeutics, such as for the identification and quantification of post-translational modifications, including oxidation. Therefore, is it crucial that the LC-MS system is performing under optimal conditions, ensuring reproducible and accurate quantitative information. A system suitability test is usually performed prior to sample analysis to confirm that the sample preparation and instrument performance are adequate and running as expected. Induced in-source oxidation is a known phenomenon associated with the electrospray process, and can be discriminated from relevant sample oxidation. On-column methionine oxidation can also take place during LC-MS/MS peptide mapping analysis of antibody-based biotherapeutics over long-term column use. This article describes how the monitoring of on-column methionine oxidation as part of system suitability testing can be used to control unintended on-column methionine oxidation of biotherapeutics. This approach minimizes the risk of measuring oxidative artifacts, and helps generate high quality data to provide reliable quantitative information about product-related heterogeneities. [ABSTRACT FROM AUTHOR]