How to Read an Epitalon Certificate of Analysis: Batch EP-2607 Line by Line
What each result means, why HPLC purity and peptide content are different numbers, and how to check the mass yourself.
The certificate of analysis for epitalon batch EP-2607, released on 1 July 2026, is published in our COA library. This walk-through uses its real numbers to show what each line means, so you can read the same document for any peptide lot. The batch code works as molecule plus year and month: EP is epitalon, 2607 is July 2026.
Identity: formula, mass and a calculation you can repeat
The certificate gives the molecular formula C14H22N4O9, a molecular weight of 390.35 and the CAS number 307297-39-8. The batch record lists a measured LC-MS mass of 390.35 Da. You can check that against the sequence yourself. Epitalon is Ala-Glu-Asp-Gly, whose free amino acids weigh about 89.09, 147.13, 133.10 and 75.07 Da, a total of 444.39. Joining four amino acids forms three peptide bonds and releases three water molecules of about 18.02 Da each, 54.05 in all. That leaves 390.34 Da, which matches the certificate to rounding.
Purity by HPLC: 99.9% against a limit of at least 98.0%
HPLC purity is the area of the main peak as a percentage of the total area of all peaks detected, usually by UV absorbance at a fixed wavelength. It tells you how much of what the detector sees is the target peptide. It does not tell you how much of the powder is peptide. The certificate also reports related substances, the largest single impurity and the total of impurities, each against a limit of 1%, and the batch is within both.
Purity is not content
The certificate lists a peptide content of 90%, a water content of 7.8% and an acetate content of 1.85%. Those three add up to roughly 100%. A lyophilized peptide powder is never all peptide: it carries water, which it absorbs readily, and a counter-ion, here acetate, that balances the charge on the peptide. So a batch can show 99.9% purity and 90% peptide content at the same time, because the two numbers answer different questions.
This matters for concentration arithmetic. If you need the net peptide concentration rather than the powder weight, multiply by the peptide content, 90% for this batch, provided the labelled amount refers to powder weight. Confirm that with the documentation for your lot rather than assuming it.
Counter-ion and solvents: acetate, TFA and residues
Solid-phase peptide synthesis typically ends with cleavage in trifluoroacetic acid, so peptides often arrive as TFA salts, and residual TFA can interfere with some cell-based assays. This batch is an acetate salt, and the certificate reports TFA as not detected against a limit of 0.5%. Residual acetonitrile and DMF are also not detected, against limits of 410 ppm and 880 ppm, and the other residual solvents tested, methanol, dichloromethane and MTBE, are not detected. Heavy metals (lead, arsenic, mercury, cadmium) are reported as not detected below 0.05 ppm each.
Water, pH, solubility and appearance
Water content is 7.8% against a limit of 8.0% or less, which is typical of lyophilized peptide and is a reason to keep the vial sealed. The pH of the solution is reported as 7.21. The powder is white to off-white and meets the solubility requirement of dissolving in water, which is why epitalon is normally reconstituted in sterile water.
Microbial and endotoxin limits
The total aerobic microbial count is below 10 cfu/g against a limit of 1,000, and the specified pathogens are not detected. Bacterial endotoxin is reported as meeting a limit of 10 EU/mg, which is a pass or fail statement rather than a measured number. If you need a numeric value, or an independent check of any result, you can send a vial to Janoshik or another laboratory. The Janoshik reports we have published so far cover other products, not epitalon, and we return the test fee as account credit.
Dates, storage and what a certificate cannot tell you
The certificate gives a manufacture and test date of 1 July 2026, a retest date of 30 June 2028, and the storage condition: light-protected and sealed. The retest date applies to the sealed lyophilized powder, not to a reconstituted solution, which should be refrigerated, divided into single-use aliquots and used promptly.
A certificate describes the lot it names and nothing else, so check that the batch code on your vial matches. QSC supplies epitalon in 10 mg and 50 mg vials strictly for laboratory research; it is not approved for human or veterinary use. For the published research on the peptide, see our evidence review.
