Quality
A supplier's purity claim is worth exactly as much as the certificate behind it
Anyone can print 99% on a product page. What separates suppliers is whether you can pull up the document, see which laboratory produced it, and match it to the physical vial in your hand. That is the only claim this business makes, and this page is how we keep it.
From synthesis to your bench
- Step 1
Synthesis and purification
Solid-phase synthesis at a GMP-audited facility, then RP-HPLC purification. Material that won't reach 99% is rejected at this stage — it is never re-listed at a lower price.
- Step 2
Fill and lyophilization
Freeze-dried, filled into nitrogen-flushed borosilicate vials, and sealed. One fill run receives exactly one lot number, so a lot always describes a single homogeneous batch.
- Step 3
Independent testing
A sample from every lot goes to Janoshik Analytical — a laboratory with no commercial interest in the result. We do not run our own purity tests and quote them as third-party.
- Step 4
Publication, then sale
The certificate is added to the public lookup before the lot is listed for sale. A lot that isn't searchable is a lot we are not shipping.
What the panel actually measures
The same six tests run on every peptide lot, so certificates are comparable across compounds and across years. No lot gets a shorter panel because it was expensive to make.
- Purity — RP-HPLC at 220 nm
- The share of the sample that is the intended peptide. Our specification is ≥ 99%. This is the number most suppliers quote and the one worth checking against an actual chromatogram, not a marketing page.
- Identity — ESI mass spectrometry
- Confirms the measured mass matches the theoretical mass for the sequence. Purity without identity is meaningless: a sample can be 99% pure of the wrong molecule.
- Bacterial endotoxin — LAL, USP <85>
- Gram-negative bacterial residue from synthesis or handling. Specification < 1.0 EU/mg. Endotoxin confounds any assay that touches an immune or inflammatory readout.
- Heavy metals — ICP-MS
- Catalyst and reagent carry-over from synthesis. Specification < 10 ppm.
- Water content — Karl Fischer
- Residual moisture after lyophilization. Specification ≤ 8.0%. High water content inflates apparent mass, so a wet vial contains less peptide than the label says.
- Appearance
- Visual confirmation of a white lyophilized cake. Discolouration or collapse means the lot is quarantined regardless of what the other tests say.
A real certificate — Semaglutide, lot RN-SEM-2608C
| Test | Method | Specification | Result |
|---|---|---|---|
| Purity (HPLC) | RP-HPLC, 220 nm | ≥ 99.0% | 99.62% |
| Identity (Mass spec) | ESI-MS | Matches theoretical | Conforms |
| Bacterial endotoxin | LAL, USP <85> | < 1.0 EU/mg | < 0.1 EU/mg |
| Heavy metals | ICP-MS | < 10 ppm | < 1 ppm |
| Water content | Karl Fischer | ≤ 8.0% | 3.2% |
| Appearance | Visual | White lyophilized powder | Conforms |
Tested August 20, 2026 by Janoshik Analytical. 35 lots are currently searchable.
Certificate lookup
Printed on every vial label. No account needed. Try .
If your test disagrees with ours
Send an accredited laboratory's report on the lot you received. If the result falls below the specification on our published certificate, we refund the order in full and reimburse the cost of your test. No restocking fee, no argument about handling, no requirement to return the vial.
We would rather pay for one contested test than defend a bad lot — and if a lot is genuinely off, we want the report before anyone else opens a vial from it. Everyone on the lot-notices list gets told the same day.
Storage and handling
Sealed vials
Store at -20 °C, protected from light. Lyophilized peptide is stable at ambient temperature for the length of a domestic transit, so a warm mailer is not a spoiled vial — what matters is where it goes after it arrives.
After reconstitution
Refrigerate at 2–8 °C and use within 30 days. Avoid repeated freeze-thaw cycles; aliquot instead. Compound-specific guidance is on every product page.
Solvent choice
Bacteriostatic water is typical for bench storage. A few peptides are poorly soluble in neutral aqueous buffer and need dilute acetic acid first — those are flagged on their product pages.
Research use only. A certificate of analysis describes the chemical identity and purity of a compound. It is not a safety assessment, not a clearance for use in any organism, and not a substitute for the risk assessment your own institution requires. Rensa Research is a chemical supplier and does not provide medical or veterinary advice.