Most suppliers in this market publish a page about their certificates of analysis. They all say roughly the same thing: the material is tested, the testing is independent, and you should feel confident.
This one is about the other half — the questions a certificate of analysis does not answer. Knowing where the document stops is what makes the part it covers useful.
A certificate describes one lot, not a product
Peptide synthesis is a batch process. Two lots of the same sequence, produced by the same route in the same facility, can differ in impurity profile, residual content, and net peptide mass.
That means a document describing a product in general says very little about one specific vial. Only paperwork tied to a lot number does. This is why a certificate carries a lot identifier, and why a certificate from a different lot — or a different vial size — is not documentation of the material in front of you.
At Prime Science Supply, a certificate is shown on a product page only when both the molecule and the vial size match what the certificate states. Where they do not match, no certificate is shown. That is deliberate. Availability of lot-level documentation varies by product and by lot.
Purity is a percentage of what the detector saw
Our published specification is ≥98% purity by HPLC-UV. It is worth being precise about what that sentence contains.
High-performance liquid chromatography separates the components of a sample by how strongly each interacts with a stationary phase as a solvent gradient carries it through a column. An ultraviolet detector records each component as it elutes, and the software integrates the area under each peak. A result of at least 98% purity means the peak corresponding to the target accounts for at least 98% of the total integrated area that the detector registered.
Two consequences follow, and neither is a criticism of the method:
A compound that does not absorb in the detector's range does not appear. UV detection responds to what absorbs UV light. A species that absorbs poorly at the monitored wavelength contributes little or no peak area, and therefore does not reduce the reported percentage.
A specification is a floor, not a measurement. Our certificates print "NLT 98.0%" — Not Less Than — in the Specification column. The measured result for an individual lot is often higher; one published GLOW Complex lot reports 98.9%. Dropping the "≥" and stating a flat percentage would convert a floor into a claim about a measured value. That is why the number always appears as ≥.
What our published certificates report
The certificates published at www.primesciencesupply.com/certificates report: appearance, solubility, water content (Karl Fischer), sodium ion (ICP-MS), residual trifluoroacetic acid, peptide purity (HPLC), related substances, bacterial endotoxins (LAL), assay (HPLC), and residual solvents by gas chromatography per USP <467>.
That is a substantial panel. It describes how much water the powder is carrying, what came along from synthesis and purification, and how much of the vial's mass is the peptide itself.
What they do not include
They do not include a separate identity test — no mass spectrometry, no UV-Vis spectroscopy.
This is the honest limit of the document, and it matters enough to state plainly. Purity by HPLC answers how much of what is in this vial is the main component. An identity test answers a different question: is the main component the molecule named on the label?
Chromatography alone does not close that second question. Retention time is consistent with an identity; it does not establish one. Mass spectrometry measures the molecular mass directly and is the standard method for confirming that the sequence in the vial is the sequence on the label.
We publish what we receive. Where a certificate does not include an identity test, we say so rather than implying a test that is not on the paper.
What to ask any supplier, including us
Four questions that a supplier either answers or does not:
- Is the certificate for the lot I will receive, and for this vial size?
- What method was used, and is the specification a floor or a measured result?
- Does the panel include an identity test, and by what method?
- Which laboratory produced the document?
A supplier that treats these as reasonable is describing material. A supplier that treats them as an obstacle is describing something else.
Where our catalog sits
Every item we list carries a ≥98% purity specification by HPLC-UV. Certificate availability and level of detail vary by product and by lot, and the product page states which is which.
If you want to see the format before ordering anything, the published certificates are here: View published certificates · or start with a catalog reference supplied as a standard reagent for cellular metabolism research: NAD+ (500 mg)
Research Use Only. Not for human or veterinary use. These products are not drugs and have not been approved by the FDA for any purpose. These statements have not been evaluated by the FDA. Prime Science Supply does not provide guidance on preparation, administration, or dosage.