This walks through a certificate field by field, in the order the fields usually appear. The worked example is a retatrutide batch, but the structure is the same for any peptide.
Header — product and batch
| Field | Example | What to check |
|---|---|---|
| Product | Retatrutide | Matches what you ordered, including any modification |
| CAS number | 2381089-83-2 | Matches the compound; absent is acceptable for novel material |
| Batch | RYZ-RETA-26071 | Matches the vial label exactly — this is the critical check |
| Manufactured | 2026-07-08 | Establishes the material's age |
| Analysed | 2026-07-14 | Should be close to manufacture, not months after |
| Retest | 2028-07-08 | The date beyond which the result should not be relied on |
The batch code is the only line that connects this document to your material. Check it before opening the vial, not after.
Appearance
Reported as conformance against a description — typically 'white to off-white lyophilised powder'. It is the cheapest test on the certificate and it still catches things: discolouration indicates degradation or contamination, and a compound that should be white arriving brown is a reject regardless of what the other lines say.
Some compounds have their own normal. GHK-Cu is deep blue in solution because of the copper coordination. NAD+ may carry a pale yellow tint within specification. Know what your compound should look like.
Purity
The headline number. What you want to see:
- The method named — 'RP-HPLC, gradient elution, UV 214 nm, area %' rather than just 'HPLC'
- The detection wavelength. 214 nm detects the peptide bond and so sees every peptide species; 280 nm sees only aromatics.
- A figure with sensible precision. 99.4% is a measurement. 99.99% is not.
- Individual related substances itemised, rather than only the total.
Where the trace is supplied, look at whether impurity peaks are resolved to baseline or sitting on the main peak's shoulder. Shoulders are where inflated figures hide.
Identity by mass spectrometry
| Field | Example | Note |
|---|---|---|
| Method | ESI-MS | Electrospray, the standard for intact peptides |
| Theoretical mass | 4731.33 Da | Calculated from the sequence |
| Observed mass | 4731.4 Da | Should agree within instrument tolerance |
| Convention | Average mass | Must match between the two figures |
If observed and theoretical disagree, the size of the gap is informative. Sixteen daltons high is oxidation. Forty-two high is acetylation. A residue-sized gap low is a deletion sequence. See the mass spectrometry guide for the full table.
Watch for a mismatch of convention. Comparing a monoisotopic observation against an average theoretical will look like a failure on a long peptide when nothing is wrong.
Water content
By Karl Fischer titration. Typical values run 3 to 8% for a lyophilised peptide. Higher figures are not automatically a reject — some compounds are strongly hygroscopic and NAD+ routinely sits near the top of that range — but higher water means shorter stability and a larger correction when you calculate concentration.
Counter-ion
Acetate or trifluoroacetate, with a level. This matters most for cell work: TFA is cytotoxic at concentrations that occur in ordinary culture conditions. If your assay involves living cells, acetate salt is the safer choice and the certificate should confirm which you have.
Net peptide content — the line most people skip
This is the field that changes your results, and it is the one most often ignored.
Chromatographic purity tells you what proportion of the peptide present is the target. Net peptide content tells you what proportion of the powder is peptide at all. They are different questions with different answers.
| Line | Value |
|---|---|
| Chromatographic purity | 99.4% |
| Water content | 3.1% |
| Acetate content | 7.2% |
| Net peptide content | 82.6% |
Weigh out 10 mg of this material and you have 8.26 mg of peptide, not 9.94 mg. If you calculate concentration from the purity figure, every solution you make is about 17% more dilute than your records say — consistently, invisibly, across every experiment run from that vial.
Footer — authorisation
The issuing laboratory should be named, with a signature or an authorised release reference. An unsigned certificate from an unnamed laboratory is an assertion rather than a record.
A five-point check
- Does the batch code match the vial?
- Are the analysis date and retest date present, and is the material still within them?
- Are the methods named, with the HPLC wavelength stated?
- Are observed and theoretical mass both given, on the same convention?
- Is net peptide content reported — and are you using it for your calculations?
Any Ryzen batch code can be checked against its certificate through the batch verification page. If a document you have been given fails any of the five checks above, that is worth resolving before the material goes anywhere near an experiment.
This guide is written for laboratory practitioners and describes analytical and handling practice. It is not medical advice, and it contains no dosing or administration guidance. Material supplied by Ryzen Research Ltd is for research use only and is not for human or veterinary use.