Selank Testing & Verification
Independent, third-party analysis of your mail-in Selank sample by RP-HPLC-UV — what the vial actually contains, measured against a certified reference standard rather than taken from the label.
What Selank is
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It is an analog of the endogenous tetrapeptide tuftsin (Thr-Lys-Pro-Arg) carrying an added C-terminal Pro-Gly-Pro tail, a modification made to slow enzymatic breakdown of the parent sequence. It is an unmodified linear peptide with no disulfide bond, no lipid side chain, and no metal complex, and it is usually supplied as a lyophilized acetate or trifluoroacetate salt for reconstitution. Analytically, two features matter more than anything else: the chain is short and unusually proline-rich, and the sequence contains no tryptophan, tyrosine, or phenylalanine — so it has no strong ultraviolet chromophore of its own. Selank is a research-market compound with no regulated manufacturing or identity guarantee, which is the reason independent verification of a specific vial is worth doing.
Why get your Selank independently tested
- Cross-labeling with Semax: Selank and Semax are sold by the same vendors, in identical-looking vials of white lyophilized powder, and frequently as a combined 'Semax/Selank' blend. Swapped labels and blends sold as a single compound are a routine failure mode. The two peptides are chemically distinct and separate chromatographically, so a retention-time and UV-spectral comparison against a certified Selank reference standard shows which peptide (or which combination) is actually in the vial.
- No aromatic residues, so identity leans on retention time: Selank contains no tryptophan, tyrosine, or phenylalanine, meaning there is no distinctive UV absorbance band above roughly 220 nm to fingerprint. Detection is at 214 nm on the peptide bond, and the UV spectrum is largely featureless. We say this plainly: for Selank the identity call rests mainly on co-elution with a certified reference standard under identical conditions, with the UV trace offering only weak corroboration. That is a real limitation of RP-HPLC-UV on this compound, and it is not the same as a mass-spectrometry sequence confirmation.
- Proline-driven degradants: a proline at position three is the classic setup for diketopiperazine formation, in which the N-terminal two residues cyclize and clip off, and the proline-rich chain is also prone to truncated and deletion-sequence byproducts from synthesis. These related substances are close in structure to the parent peptide and can sit near the main peak. Chromatographic purity reported as area percent quantifies how much of the UV-absorbing material is actually the target peak.
- Early elution crowds the main peak: a short, highly polar, proline-rich peptide is weakly retained on reversed phase and elutes early, near where salts, counterions, and bulking agents come off the column. Run on a method that is not optimized for polar retention, unretained matrix and polar impurities can crowd or co-elute with the analyte and quietly inflate an area-percent figure. Selank needs a polar-retentive gradient for the purity number to mean anything.
What we measure on Selank
Each Selank sample is run by reversed-phase HPLC with UV/diode-array detection at 214 nm on a gradient chosen to retain a short, polar, proline-rich peptide, and compared against a certified Selank reference standard. The certificate reports exactly three results: identity, by retention-time match to the reference standard run under the same conditions with UV-spectral comparison as supporting evidence (Selank has no aromatic residue, so the spectral contribution here is limited and we treat retention time as the primary evidence); chromatographic purity, as the area percent of the main peak against total integrated peak area; and net-peptide assay, as milligrams of peptide per vial. Where a Semax/Selank blend is submitted, the components are resolved and reported separately if the method and available reference standards allow.
Every result is issued as a certificate of analysis you — or anyone you forward it to — can verify cryptographically. Reporting identity, purity, and milligram content is the point: a vial can be pure and still underfilled, so we report all three. More on purity vs. net-peptide content and how to read a peptide COA.
Our scope — stated plainly
Testing is RP-HPLC-UV against a certified reference standard. We do not perform mass spectrometry, sterility, endotoxin, heavy-metal, or residual-solvent testing. Because Selank is a less-common compound, a certified reference standard may need to be sourced before analysis, which can add lead time; we confirm that with you before running the sample. KMD Analytical is an independent laboratory and does not sell peptides.
KMD is an independent RP-HPLC-UV lab. We do not run LC-MS / mass-spec, sterility, endotoxin, or heavy-metal testing. If your job needs a capability we don't have, we'll say so.
Selank testing — FAQ
Can you tell Selank apart from Semax, or check a Semax/Selank blend?
Yes, where the two resolve chromatographically — they are different peptides with different retention behavior under our method. For a blend we report each resolved component separately, and can provide a net-peptide figure per component where a certified reference standard is available for each. Reference standards for both may need to be sourced first, which we confirm before the run.
Selank has no aromatic amino acids. How solid is the identity result?
It is an honest retention-time match, not a structural proof. With no tryptophan, tyrosine, or phenylalanine, Selank produces no characteristic UV band above about 220 nm, so the diode-array spectrum adds only weak corroboration and the identity call rests on your sample co-eluting with a certified Selank reference standard under identical conditions. That is strong evidence against a substituted peptide with different retention, but it is not mass spectrometry and it does not confirm the amino-acid sequence. If you need definitive mass or sequence confirmation, that requires LC-MS, which is outside our scope.
What does net-peptide content mean for a Selank vial?
It is the milligrams of actual peptide in the vial, which is not the same as the weight of the powder. Lyophilized Selank also carries acetate or TFA counterions bound to its lysine and arginine residues, residual moisture, and any bulking agent, so total powder mass overstates peptide mass. The assay reports peptide milligrams specifically, so you can compare that against the labeled figure.
Do you report anything about how the peptide behaves biologically?
No. We report three analytical results only — identity, chromatographic purity, and net-peptide content for the sample you mail in. Nothing on the certificate is a statement about safety, quality, suitability for any use, or biological activity.
Other peptides we test
Retatrutide · Cagrilintide · Tesamorelin · BPC-157 · see the full panel.