Understanding Peptide Purity | HPLC, Mass Spectrometry & COA Guide
QSC · RESEARCH CATALOG
Understanding Peptide Purity: HPLC, Mass Spectrometry & COA What ≥99% HPLC Means · Mass Spectrometry Identity · Net Peptide Content · Janoshik Verification
Purity in the context of research peptides refers to the fraction of the sample that is the target peptide vs impurities. The primary measurement is HPLC (High-Performance Liquid Chromatography) purity, expressed as a percentage. A 99% HPLC purity result means 99% of the measurable sample is the target peptide with 1% impurities. Research-grade standard is ≥99%. Some suppliers use ≥98% as their threshold.
Purity in the context of research peptides refers to the fraction of the sample that is the target peptide vs impurities. The primary measurement is HPLC (High-Performance Liquid Chromatography) purity, expressed as a percentage. A 99% HPLC purity result means 99% of the measurable sample is the target peptide with 1% impurities. Research-grade standard is ≥99%. Some suppliers use ≥98% as their threshold.
What Impurities Are Present?
Common impurities in research peptides include: truncated sequences (incomplete synthesis chains), deletion peptides (sequences with one amino acid missing), oxidized peptides (particularly tryptophan/methionine/cysteine residues), deamidated variants, and aggregated forms. A COA with a full chromatogram identifies all peaks — a purity number alone does not. QSC COAs include the full HPLC chromatogram.
Mass Spectrometry: Confirming Identity
HPLC tells you purity percentage. MS (mass spectrometry) tells you identity — that the compound matches the target peptide’s theoretical molecular weight within acceptable tolerance (typically ±0.01%). A peptide could theoretically be 99% pure but be the wrong compound. MS prevents this. All QSC COAs include both HPLC purity and MS identity confirmation.
Net Peptide Content vs HPLC Purity
HPLC purity measures the peptide fraction vs other organic compounds. Net Peptide Content (NPC) measures the peptide mass as a fraction of the vial’s total mass — accounting for residual water and counterion salts (TFA/acetate). A peptide can be 99% pure by HPLC but only 70% by NPC — the 30% difference is bound water and salt. NPC matters for accurate dosing calculations. QSC provides NPC on COAs where applicable.
Independent vs In-House COA: The Critical Difference
An independent COA comes from a third-party laboratory not affiliated with the supplier — Janoshik, MZ Biolabs, Colmaric. The results are published by the independent lab and cannot be altered post-publication. An in-house COA is issued by the supplier’s own lab — self-generated and unverifiable by any external party. QSC uses Janoshik exclusively: every batch result is published at verify.janoshik.com with a unique batch code that any researcher can use to verify independently.
Frequently Asked Questions
What is ≥99% HPLC purity for research peptides?
≥99% HPLC purity means high-performance liquid chromatography shows ≥99% of the sample is the target peptide with ≤1% impurities. This is the research-grade standard. The number should be accompanied by a chromatogram graph — not just stated as a number. QSC COAs include the full chromatogram from Janoshik independent laboratory.
How do I verify a Janoshik COA?
Every QSC order includes the Janoshik batch verification code. Visit verify.janoshik.com, enter the batch code, and the result appears directly from the Janoshik database — showing HPLC purity percentage, mass spectrometry result, and compound name. This process requires zero trust in QSC: you verify directly with the independent laboratory.
Why does Peptide Sciences’ internal COA matter less than Janoshik?
Peptide Sciences used internal COA testing — self-generated by their own lab, unverifiable by external parties. There is no way to independently confirm an internal COA result. Janoshik publishes results post-test on their own platform (verify.janoshik.com) — a supplier cannot alter or remove a published Janoshik result. The difference is verified third-party accountability vs. unverifiable self-reporting.
Research Use Only: All QSC products sold strictly for in vitro laboratory research. Not for human or veterinary use. Information on this page is educational and does not constitute medical advice.
