Three retatrutide COAs, three peak times: 6.2, 11.8 and about 15.2 minutes

ON THIS PAGE

1. Key findings
2. The same compound, three retention times
3. What a retention time alone can and cannot prove
4. A vendor's own document naming its limits
5. What three certificates cannot settle
6. Limitations and open questions
7. Sources

This publication's own field guide to reading a chromatogram explains the rule in the abstract: a retention time is a fact about the column, the detector, and the gradient a lab chose, not a fact about the molecule itself. Three certificates in this ledger, all describing the same 10mg retatrutide vial, show what that rule looks like once real numbers are next to each other.

The same compound, three retention times

Forward Peptides' retatrutide certificate, read 2026-08-25, reports its single main peak at retention time 6.220 minutes, by HPLC with diode-array detection read at 220nm. Alpha Pro Peptides' retatrutide certificate, read 2026-08-26, reports one peak near 15.2 minutes, by HPLC with UV detection coupled to mass spectrometry. American Peptides' retatrutide certificate, also read 2026-08-26, reports a single peak at 11.778 minutes, by reversed-phase HPLC at 214nm. Three certificates, one compound, and three retention times that share nothing with each other: 6.220, 11.778, and roughly 15.2 minutes. None of the three is wrong. Each number is exactly what this publication's own reference piece predicts a retention time will be, a fact about that lab's own column and gradient on that day, not a number a buyer could use to check one certificate against another.

What a retention time alone can and cannot prove

Forward Peptides' certificate is the sharpest illustration of a second rule from the same reference piece: a retention time proves the method ran, nothing more. The document states its identity finding as "identity Retatrutide CONFORMS," resting on that single UV peak at 6.220 minutes, with no mass spectrometry anywhere on the certificate to confirm what actually eluted at that time. The other two certificates do not share this gap. Alpha Pro Peptides' certificate backs its retention time with a matching mass panel, reporting specific charge states for the compound at the same peak. American Peptides' certificate separately reports identity by LC-MS/MS as its own analytical row, distinct from the purity figure tied to the retention time. A peak at a stated time is a fact about something that left the column and absorbed at one wavelength. Whether that something was actually retatrutide is a different question, and only two of these three certificates answer it with a second, independent method.

A vendor's own document naming its limits

Alphamino's own certificate, read 2026-08-26, for a different compound in its catalog, states its purity figure carefully rather than as a bare percentage: it reports 99.3 percent as a Peak Purity Index measure, by HPLC-UV at 215nm. Naming the measure does the same work this publication's reference piece describes area percent doing in general: it is arithmetic over what one detector saw, at one wavelength, not a claim about the mass fraction of the vial. A certificate that names its own measure this specifically is doing a buyer a favor that a bare, unlabeled purity percentage does not.

What three certificates cannot settle

Reading three certificates side by side answers a narrower question than it might first appear to. It does not establish which lab's method is more rigorous, since a shorter or longer retention time says nothing about accuracy on its own. It does not establish that Forward Peptides' vial is mislabeled, since a UV-only identity finding is a documentation gap on the certificate, not proof the compound is wrong. What three certificates for the same nominal product do establish is the reference piece's own point, made concrete: a retention time is not a number a buyer can use to compare one seller's certificate against another's, and a certificate resting identity on retention time alone is answering a narrower question than one that backs it with mass spectrometry.

Limitations and open questions

This piece describes four dated certificates, read 2026-08-25 and 2026-08-26, and a vendor's published certificate can change at any time after those dates. This piece takes no position on which laboratory's method is more accurate, or on whether Forward Peptides' identity finding is correct; it reports what each document states and what it does not. The technical framework this piece applies, including why retention time belongs to the method and what a related-substance peak requires to be named, is covered in full in this publication's own separate reference piece on chromatograms, which this piece does not repeat.

Three certificates for the same vial, three retention times, and only two of them backed by a method that can actually say what eluted. The number on the time axis was never the part worth comparing.

Sources

This publication's own reference piece on chromatograms, "Reading a Chromatogram: a Field Guide," published 2026-09-10, for the technical principles applied above. Supplier observations are this publication's own, from the dossier record in ledger/vendors.json: Forward Peptides, read 2026-08-25; Alpha Pro Peptides, American Peptides, and Alphamino, all read 2026-08-26. Vendors are named here, never linked, per site policy.