A purity number without a chromatogram is a marketing claim. This is how to read a certificate of analysis field by field, and what Restore Labs puts on every lot.
Two analytical techniques do the heavy lifting on any research peptide release. HPLC answers "how much of this vial is the target molecule?" LC-MS answers "is the target molecule actually the one on the label?" Neither answers the other's question, which is why a compliant certificate carries both.
Certificate fields, and what each one proves
| Field | What it proves |
|---|---|
| Lot identifier | Traceability back to a single synthesis run |
| HPLC purity % | Proportion of target peptide versus deletion and truncation sequences |
| HPLC method | Column, mobile phase and gradient — without it the % is unreproducible |
| LC-MS observed mass | Molecular identity within ±0.5 Da of theoretical |
| Counterion and % | Acetate or TFA content, which determines net peptide mass |
| Water content | Karl Fischer or TGA figure affecting the same mass calculation |
| RUO statement | Explicit research-use-only classification |
Red flags that should fail a batch
- A purity percentage published with no chromatogram image attached
- A mass figure with no LC-MS trace behind it
- The same lot number appearing across multiple shipments
- Blend products quoting a single combined purity instead of per-component figures
- No counterion or water-content data anywhere on the document
The Restore Labs documentation standard
- Lot-specific certificate on every vial, never a generic product-level PDF
- HPLC chromatogram and LC-MS trace included as images, not summarised
- Independent third-party verification available on request for any batch
- Certificates archived against the lot so they can be re-issued years later
Purity testing FAQ
What HPLC purity is standard for research-grade peptides?
≥98% generally, and ≥99% is expected for shorter sequences under roughly 30 residues.
Why does counterion content matter?
A vial labelled 10 mg containing 12% acetate holds less than 10 mg of peptide. Ignoring the counterion silently shifts every concentration calculation downstream.
Research use only. Every Restore Labs article is in-vitro and laboratory reference material for qualified Australian researchers. Nothing here is medical, therapeutic, dosing or performance guidance for human or veterinary use.
