Lab Quality & Testing
Peptide Impurities Explained: Truncations, Deletions and Oxidation Products
The impurities that matter in synthetic peptides are usually close relatives of the target sequence. What they are, where they come from, and how they are detected.
Published October 4, 2026 · 7 min read
By Novanta Research Editorial Team
Evidence scope: Analytical evidence only. Impurity profiles describe chemical composition and do not establish biological activity, clinical safety or suitability for human use.
Synthesis-related impurities
Solid-phase synthesis builds a peptide one residue at a time, and each coupling step can fail partially. The result is a family of related impurities: deletion sequences missing one residue, truncation products where the chain stopped early, and incompletely deprotected intermediates.
Because these species differ from the target by a single residue or protecting group, they often elute close to the main peak and can be difficult to resolve without a well-developed chromatographic method.
Sources for this section
- Related impurities in peptide medicines — Journal of Pharmaceutical and Biomedical Analysis, 2014
Degradation-related impurities
After synthesis, peptides continue to change. Oxidation at methionine adds sixteen daltons; deamidation at asparagine and glutamine shifts mass by roughly one dalton; aggregation creates non-covalent or covalent multimers that may not appear as separate peaks at all.
Storage temperature, moisture, light, pH and freeze-thaw history all influence which degradation pathways dominate, which is why handling conditions are part of the impurity story.
Sources for this section
- Factors affecting peptide stability and aggregation — Interface Focus / PMC, 2017
How impurities are detected
Reversed-phase HPLC with UV detection is the workhorse for peptide-related impurities, reported as area percent against a stated integration threshold. Mass spectrometry identifies what an impurity is by its mass shift, and LC-MS couples the two so each peak carries a mass spectrum.
No single method sees everything. ICH Q2(R2) requires that specificity — the ability to distinguish the analyte from its likely impurities — be demonstrated for the intended procedure rather than assumed.
Sources for this section
- Validation of Analytical Procedures Q2(R2) — International Council for Harmonisation, 2023
- Related impurities in peptide medicines — Journal of Pharmaceutical and Biomedical Analysis, 2014
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For laboratory and research use only. Not for human or veterinary consumption. Novanta Research is not a compounding pharmacy and nothing in this article is medical advice or a claim that any compound diagnoses, treats, cures or prevents any condition.