HPLC Purity ≥ 99%: How to Interpret a Certificate of Analysis
Chromatography, mass spectrometry, lot-by-lot traceability: what a Janoshik CoA actually demonstrates and why it matters.
A Certificate of Analysis (CoA) is the central document accompanying every research peptide. Without it, no experimental data is defensible. This article explains what a CoA actually demonstrates — and what it does not.
What is a CoA?
A Certificate of Analysis is a report produced by a third-party analytical laboratory independent of the supplier. It attests to the chemical identity, purity, and quantification of a specific lot — not a generic product. In European peptide research, Janoshik Analytical (Czech Republic) has become the reference shared by most serious suppliers.
Report traceability: lot, date and task number
A CoA is only meaningful if it is tied to an identifiable lot. A Janoshik report states the task number assigned by the laboratory, the analysis date, the method used and the measured quantity. Those elements are what link a vial to a specific analysis, rather than a generic document reused from lot to lot.
> A PDF with no report number, date or method offers no guarantee: it is lot-by-lot traceability that gives the document its value. We publish the full reports on our CoA page, with their task number and analysis date.
The HPLC chromatogram: what "99%" really means
High-performance liquid chromatography (HPLC) separates the components of a sample according to their affinity for a stationary phase. For a pure peptide, one observes:
- a strongly predominant main peak;
- a stable baseline, without drift;
- the absence of significant secondary peaks.
The statement "≥ 99.0% HPLC" means that the integrated area of the main peak represents at least 99% of the total area detected by the system. The remaining <1% corresponds to residual impurities: truncated peptides (incomplete synthesis), salts, trace solvents. Below 99%, impurities can bias a pharmacokinetic or receptor-binding study to the point of making it uninterpretable.
Mass spectrometry (MS): confirming identity
HPLC measures purity, but not identity. That is the role of mass spectrometry.
The spectrometer ionizes the molecule and measures its mass-to-charge ratio. The measured molar mass must match the theoretical mass calculated from the sequence, generally within ± 1 Da. A larger discrepancy indicates:
- an incorrect sequence;
- a post-synthesis modification (acetylation, oxidation);
- contamination by a closely related peptide.
It is this dual HPLC + MS validation that makes a CoA scientifically admissible.
Quantification: how much peptide is actually in the vial
The CoA also indicates the actual mass contained in the vial. For a product labeled at 10 mg, one typically expects a quantification between 9.7 and 10.3 mg. This control prevents underdosing, which would distort any downstream analytical use.
Why a "per lot" CoA rather than a generic one
Each synthesis is a unique chemical event. Two lots of the same peptide, produced on the same line, are never strictly identical: purity of 99.2% versus 99.7%, quantification of 9.9 mg versus 10.1 mg. A generic CoA, presented as valid for all lots, is by construction non-compliant with analytical standards.
All Peptinium Labs peptides are characterized lot by lot. You can view a few public CoA examples to see what compliant documentation looks like — for example those for BPC-157 or KLOW.
Beyond the CoA: what it does not tell you
A CoA attests to chemical identity and purity at the point of synthesis. It says nothing:
- about the stability of the molecule over time (which depends on storage);
- about biological effects (which fall under the published scientific literature);
- about regulatory compliance for any use other than research.
To understand stability and storage, see our article on cold chain management in the laboratory.