A blend certificate has to do twice the work of a single-compound one, and this is the catalogue's clearest example. The Selank + Semax blend is two heptapeptides co-lyophilized in one vial at a nominal 5 mg each, and its certificate, COA7604 for lot SEMSEL5-0803, reports two identities, two contents, two retention times and one purity. The blend certificate post explains why that structure is the only honest one for a mixture; the share-a-bottle post explains why these two particular peptides can be stored together. This post reads this lot's certificate line by line and answers the question the search phrase asks: what does the Selank + Semax COA actually say?
What two identities in one certificate look like
The two compounds first, because the certificate makes sense only against them.
| Semax | Selank | |
|---|---|---|
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Formula | C37H51N9O10S | C33H57N11O9 |
| Average mass | 813.9 | 751.9 |
| CAS | 80714-61-0 | 129954-34-3 |
| Net charge near pH 7 | about zero | about plus 2 |
| Reactive residues | methionine, histidine | none |
| Aromatic residues | phenylalanine, histidine | none |
Both share the C-terminal Pro-Gly-Pro, which is the structural reason they are so often paired; the Semax post and the Selank post cover each on its own. What matters here is that they differ by 62 daltons in mass and by a great deal in polarity, and both differences are what the certificate relies on.
What does lot SEMSEL5-0803 report?
Issued by Bioviridian Inc. on 17 August 2026. Five tests, two of them reported per component.
| Test | Method | Semax | Selank | What it establishes |
|---|---|---|---|---|
| Identity | LC-MS/MS | 813.9 | 751.9 | Both intact peptides present at their predicted masses |
| Retention | RP-HPLC, 214 nm | 9.39 min | 2.29 min | Two resolved peaks, far apart |
| Content | Gravimetric against label | 5.15 mg | 5.37 mg | Each component slightly over its 5 mg nominal |
| Purity | RP-HPLC, 214 nm | 99.76% (whole run) | 99.76% of the UV-absorbing area is the two main peaks together | |
| Endotoxin | LAL | < 0.05 EU/mL | Below the reporting limit | |
| Heavy metals | ICP | < 0.01 ppm | Below the reporting limit |
Which peak is which, and why retention tells you
Selank elutes at 2.29 minutes and Semax at 9.39. The seven-minute gap is the chemistry of the two sequences. Selank carries a lysine and an arginine, no aromatic residue and a C-terminal proline; it is a polar, cationic peptide that barely holds on a reversed-phase column and comes off near the solvent front, the same region where vilon elutes. Semax carries a methionine, a histidine and a phenylalanine, which together give it enough hydrophobicity to retain well into the gradient.
That gap is what makes a blend certificate possible. Two peaks seven minutes apart can be integrated separately, assigned by their masses, and reported with a content each. Two peptides that co-eluted could not be, and the blend certificate post explains why a single number across an unresolved pair would be meaningless. The chromatogram post covers how to read the two peaks.
The single purity figure, 99.76%, is the two main peaks' combined area over the whole run's area. It says that almost nothing in the vial is neither Semax nor Selank. It does not say how pure each component is on its own, which is a question the identity and content lines answer between them. The area-percent post sets out what the percentage means.
Content per component and the molar ratio
The label says 5 mg of each. The certificate says 5.15 mg of Semax and 5.37 mg of Selank. Divide by the masses:
| Component | Content | Mass | Micromoles |
|---|---|---|---|
| Semax | 5.15 mg | 813.9 | 6.33 |
| Selank | 5.37 mg | 751.9 | 7.14 |
The vial is 1 to 1.13 by moles, Selank in slight excess, for two reasons that stack: it was filled a little heavier and it is the lighter molecule. A 1 to 1 mass blend of two compounds with different masses is never 1 to 1 by moles, and a design that needs equimolar amounts should use the certificate's figures, as the molarity post recommends, or buy the two compounds separately and mix to the ratio it needs. The blends versus single compounds post covers when each choice is right.
Handling set by the less robust component
Semax has a methionine, which oxidises, and a histidine, whose charge moves around pH 6. Selank has neither. So the vial is handled as a Semax vial: degassed diluent for sensitive assays, cold storage, aliquots thawed once, and a buffered working stock. The share-a-bottle post explains why that is the rule for any blend, and the oxidation post covers the methionine chemistry. Both peptides are small and reasonably soluble; Selank's two positive charges make it the one more likely to adsorb at nanomolar concentration, per the adsorption post.
At the listed price of $70 for 5 mg of each, the vial is about $5.20 per micromole across the two.
Frequently asked questions
Which number on the certificate is Semax and which is Selank?
Match the masses. 813.9 is Semax, 751.9 is Selank. The contents and retention times are reported in the same order, Semax then Selank, and the retention times confirm it: the polar Selank elutes first.
Why is there only one purity figure?
Because purity by HPLC is the share of the run's area in the main peaks, and for a blend the main peaks are two. 99.76% means almost nothing else is present. Per-component purity would need each compound run alone.
Is the vial 1 to 1?
By label mass, yes. By certificate content, 5.15 to 5.37 mg. By moles, 6.33 to 7.14 micromoles, a ratio of about 1 to 1.13.
Why do the two peptides separate so cleanly?
Selank is polar and cationic with no aromatic residue; Semax has a methionine, a histidine and a phenylalanine. Seven minutes of retention difference is the result.
What is the blend sold for?
Laboratory research. Every product on this site is for in-vitro research use only and not for human or animal use.
References
- PubChem, National Library of Medicine. Semax, CID 9811102, C37H51N9O10S, CAS 80714-61-0; Selank, CID 11765600, C33H57N11O9, CAS 129954-34-3. Read 2 October 2026. pubchem.ncbi.nlm.nih.gov/compound/9811102
- Bioviridian Inc. Certificate of analysis COA7604, lot SEMSEL5-0803, issued 17 August 2026. Verification code on the certificate. bioviridians.com/coa-search.html
Every product mentioned is sold for laboratory research use only and is not for human or animal use. Nothing on this page describes or recommends use of the material sold here in humans or animals.
