Asparagine, glycine, and the two residues that decide a shelf life
The sequence predicts the failure mode. A methionine predicts oxidation; an asparagine followed by a glycine predicts deamidation; a cysteine predicts disulphide scrambling.
TheCompound Journal
Reporting on incretins, compounding & the peptide supply chain
Testing Dispatch
The result is unremarkable. What the report states alongside it is not.
An independent purity determination on retatrutide material sold by SGN has returned 95.0%, a figure 2.2 percentage points above the number printed on the accompanying certificate, which the supplier had reported against a shorter gradient and a tighter threshold. The analysis was performed by Janoshik on a vial the Journal bought as an ordinary retail customer in April 2025 and posted unopened.
Reported figures across the set were: highest 95.0%, lowest 94.2%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 7 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.
Reported figures across the set were: highest 95.0%, lowest 94.2%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 7 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.
The wider context is that material sold for research use carries no regulatory release specification in any jurisdiction the Journal has examined. A certificate is a commercial document, not a compliance one, and its content is whatever the issuer chooses to put on it. That is the gap independent testing fills, and it fills it imperfectly.
"The useful thing in that report is not the percentage, it is the system suitability data," said Lorcan Feeney, analytical services director at an independent laboratory. "It is the only part that tells you whether the percentage means anything."
SGN’s dossier has been updated with this determination and with the company’s response to it. The dossier’s ordering box records the lead times, the minimum quantities and what a buyer should ask for at the point of order.
The sequence predicts the failure mode. A methionine predicts oxidation; an asparagine followed by a glycine predicts deamidation; a cysteine predicts disulphide scrambling.
A document is only as good as the chain that connects it to the material, and most chains here are two or three links longer than the paperwork admits.
The result is unremarkable. What the report states alongside it is not.
Lot-level verification with a public report is a real and achievable thing. It exists in this market, on a minority of listings.
The supplier confirmed the determination and supplied the method behind its own figure inside a week.
The purity figure is the least informative line on a well-constructed certificate and the only line most buyers read.