Related Experiment Video
Updated: May 8, 2026

Large Scale Non-targeted Metabolomic Profiling of Serum by Ultra Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS)
Published on: March 14, 2013
Characterization of a low-level unknown isomeric degradation product using an integrated online-offline top-down
Xiang Yu1, Christopher Warme, Dinah Lee
1Structure Elucidation Group, Global Process & Analytical Chemistry, Merck Research Laboratories , 556 Morris Ave., Summit, New Jersey 07901, United States.
Abstract:
An integrated online-offline platform was developed combining automated online LC-MS fraction collection, continuous accumulation of selected ions (CASI), and offline top-down electron capture dissociation (ECD) tandem mass spectrometry experiments to identify a low-level, unknown isomeric degradant in a formulated drug product during an accelerated stability study. By identifying the diagnostic ions of the isoaspartic acid (isoAsp), the top-down ECD experiment showed that the Asp9 in exenatide was converted to isoAsp9 to form the unknown isomeric degradant. The platform described here provides an accurate, straightforward, and low limit of detection method for the analysis of Asp isomerization as well as other potential low-level degradants in therapeutic polypeptides and proteins. It is especially useful for unstable and time-sensitive degradants and impurities.
Related Concept Videos
Peptide Identification Using Tandem Mass Spectrometry
This technique helps gather information regarding the protein from which the peptide was obtained and to study the peptides’ amino acid sequence. Identifying peptides from a complex mixture is an important component of the growing field of...
Tandem Mass Spectrometry
Mass Spectrometry: Complex Analysis
GC–MS is a powerful hyphenated method commonly used in forensics and environmental...
High-Resolution Mass Spectrometry (HRMS)
MALDI-TOF Mass Spectrometry
Mass Spectrum: Interpretation
