Thymosin-Alpha 1 (A1) lab tests

Seven checks before you trust a Thymosin-Alpha 1 (A1) certificate

The same seven questions decide whether a certificate of analysis means anything, whichever compound it describes. Six are about the document; the seventh is about what no document can tell you.

1. An independent, batch-matched COA. The certificate must name the batch or lot in your hands, and must come from a laboratory the vendor neither owns nor pays. A specimen certificate from an earlier lot proves nothing about the vial you were sent.
2. HPLC purity, read against a known band. A purity figure is only informative against the distribution for that compound. "Above 98%" is not a claim — the useful question is whether the result sits inside the range the rest of the market reports. How to read HPLC and mass-spec results.
3. Mass-spectrometry identity. HPLC says how much of the sample is one thing; it does not say which thing. Only a mass-spec result establishes identity, and it is the only check that separates compounds a few daltons apart. Contamination is not hypothetical: research-grade custom peptides from two independent commercial suppliers were found to carry contaminating peptides at roughly 1% by weight, enough to produce false-positive results in immunology assays (Clinical and Vaccine Immunology, 2008 — a study of HIV vaccine peptide libraries rather than of any compound on this site).
4. Net content, measured rather than assumed. Purity and quantity are different questions: a vial can be 99.7% pure and still contain two thirds of the labelled mass. Why 10 mg isn't 10 mg.
5. Endotoxin (LAL) on the batch. An absent endotoxin line means the batch was not tested — not that it passed. Endotoxin testing and LAL interpretation.
6. Who ran the test, and what they left off. A laboratory with a record on this compound, named on the certificate, with a verification route back to it. Testing laboratories we track · Red flags in a certificate of analysis.
7. What no test on the vial can establish. A perfect certificate confirms that a vendor sold the correct molecule at the stated quantity. It says nothing about efficacy, dosing, or long-term safety.

Want a vial tested yourself? How to send a peptide for independent HPLC testing.

What thymosin alpha-1 testing has to rule out

Thymosin alpha-1 (thymalfasin) is a defined 28-residue peptide, Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN, N-terminally acetylated, with the formula C₁₂₉H₂₁₅N₃₃O₅₅ and a molecular weight of 3,108.3 g/mol (exact mass 3,107.51). The expected mass is established, published and consistent across sources, so mass spectrometry against it genuinely resolves identity — which is not true of every compound sold beside it. The identity-critical feature is the acetyl group: it is part of the molecule, a non-acetylated (des-acetyl) form is 42 Da lighter and a different compound, and HPLC purity will not distinguish the two.

Three different substances are sold under the word thymosin. Thymosin beta-4 and its fragment TB-500 are entirely different molecules from thymosin alpha-1. Thymalin is an undefined calf thymus extract with no single mass to confirm, no sequence to print on a certificate and no specification a laboratory could hold a batch against.

Measured content is the weaker axis on this compound. As of August 2026 it ran −18.8% to +14.6% against label, with most results within ±5%; one vendor's product labelled 13 mg tested at 10.56 mg, an 18.8% shortfall, and two others returned roughly +14% overages. A price per milligram assumes the milligrams are in the vial.

• A batch-matched mass spectrum at 3,108.3 Da, read specifically for the N-terminal acetyl. A certificate reporting an HPLC purity figure and nothing else has not confirmed identity at all.
• The correct PubChem record, CID 16130571. CID 16130265 is not thymosin alpha-1 — it is a 14-residue peptide, C₈₁H₁₁₄N₁₆O₃₀, auto-titled "Tyifevefqkeedd" — and it is cited for Tα1 often enough to be worth checking directly. Paperwork quoting it has copied an identifier rather than verified one.
• CAS 62304-98-7 or 69521-94-4 (both are legitimate) and UNII W0B22ISQ1C. Thymalfasin names the same substance, so a listing that treats thymalfasin and thymosin alpha-1 as separate products, or that cannot produce any identifier, was assembled from other listings rather than from a specification.
• Fill quantity as its own line, as a quantitative content figure separate from the purity percentage.
• Endotoxin (LAL): results appear sporadically rather than routinely on this compound, with compliant samples passing at ≤0.05 EU/mL. FDA named immunogenicity and peptide-related impurities as its stated concerns for this substance in writing, which makes the LAL result the test that speaks to the specific issue on the record.
• Because every one of these checks is answerable for thymosin alpha-1, a vendor who declines to answer has made a choice rather than met a limit.