Every peptide lot sold by Helix ships with a Certificate of Analysis (CoA) generated by an independent third-party laboratory — Janoshik Analytical in Germany for our current lots. The CoA is the only objective record that the contents of your vial match the molecule, the sequence, and the purity claimed on the product page. Learning to read it takes about ten minutes; here's what every section means.

1. HPLC purity — the main purity number

HPLC (High-Performance Liquid Chromatography) separates the molecules in your sample by their chemical interactions with a column. For a research peptide, you're looking at reverse-phase HPLC at 220 nm, which detects peptide bonds.

The chromatogram shows peaks at specific retention times. For a pure peptide, you'll see one dominant peak (your target compound) plus a few minor peaks (impurities, truncated sequences, oxidation products, residual solvents). The area-under-curve percentage of the dominant peak is your purity number.

What good looks like: ≥99% main-peak area for a research-grade peptide. Most published synthesis papers report ≥98% as acceptable; we hold our lots to ≥99% because the marginal cost of additional purification is small relative to the data-quality cost of an unknown impurity.

Red flags: Purity <97%, multiple impurity peaks of similar height to the main peak (suggests incomplete synthesis), or a large early-eluting peak (suggests residual solvent contamination rather than peptide impurity).

2. Mass spectrometry — confirming the molecule is the molecule

Mass spec (typically ESI-MS, electrospray ionisation mass spectrometry) measures the molecular weight of your peptide to within ~1 Da. The CoA should show a single peak at the expected molecular weight, with the observed value matching the theoretical value within the instrument's mass accuracy (typically ±0.1% for high-res instruments).

What good looks like: A single peak at the calculated molecular weight. The instrument-reported mass error (in ppm or Da) should be within ±0.5 Da for peptides <5 kDa.

Red flags: Multiple peaks of similar intensity (mixture), a peak at half the expected mass (suggests the dimer dissociated during ionisation — usually fine), or a peak at +16 Da (oxidation of methionine — common if the peptide sat at room temperature with dissolved oxygen).

3. Endotoxin (LAL)

Limulus Amebocyte Lysate (LAL) testing measures bacterial endotoxin contamination. For research-grade peptide used in cell culture, endotoxin matters because even low-level contamination will activate immune cells and confound inflammation-related assays.

What good looks like: <5 EU/mg for research-grade peptide used in cell culture. For peptides destined for any animal work, <1 EU/mg is preferred.

Red flags: >10 EU/mg indicates either poor aseptic technique during synthesis or vialing, or aged peptide with microbial growth.

4. Residual solvents

Peptide synthesis uses solvents like acetonitrile, methanol, and TFA. USP <467> sets limits on how much can remain in the final product. The CoA should list each solvent tested and the amount found, all below the ICH Q3C(R8) limits.

What good looks like: All detected solvents at or below the ICH limit. Most research-grade lots come in well below the limits (typically <10% of the limit for acetonitrile).

5. Sterility & filter specification

Many peptide CoAs report that the product is filtered through a 0.22 μM membrane. This is the standard sterilising-grade filter pore size for aqueous solutions. Filtered ≠ sterile (filtering a contaminated solution still gives a contaminated product), but it indicates that aseptic technique was used during vialing.

6. Lot number and traceability

Every vial should carry a printed lot number that matches the lot number on the CoA. The lot number format we use is HX-[SKU]-[year]-[quarter]-[batch] — for example HX-SM5-2026-Q3-A2. The CoA lot number, the vial label lot number, and the shipping manifest lot number should all match exactly.

If they don't, that's a serious supply-chain integrity issue — the product may be a relabel, a swap, or a dilution. Don't use it; contact the vendor.

What to do if the CoA doesn't match the vial

This is the single most important question in peptide procurement. The whole point of third-party verification is to give the buyer an objective check that doesn't depend on trusting the seller. If your CoA's lot number doesn't match the vial, or if the HPLC purity is below what was claimed on the product page, the supplier has a contractual obligation to make it right.

Helix's refund policy, in plain language: if the CoA you receive doesn't match the published CoA for the lot on your vial label, you get a full refund. We don't argue, we don't require you to send the product back first, and we don't make you justify the claim beyond a photo of the lot label and the CoA.

That's the standard the industry should hold itself to. Not every vendor does.

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Janice Soegianto is the head of verification at Helix Peptide Research. She previously ran quality operations at a Shanghai-based synthesis facility and has reviewed more than 4,000 peptide CoAs since 2019.