Most research compound suppliers look identical from the outside. Same product names, same purity figures, same promise of a certificate. The differences only appear when you ask specific questions, and most of them can be asked before you spend anything.
This is the list we would use. It is written knowing we are one of the suppliers being assessed by it.
1. Can I see the certificate before I order?
The answer should be yes, immediately, without a form.
“Available on request” usually means available after purchase, which is too late to be useful. “Available to verified customers” means the same thing with extra steps.
A supplier confident in their analysis publishes it. One who is not, does not.
2. Is the certificate for the batch I will receive?
This is the question that catches the most suppliers, and the failure is usually carelessness rather than dishonesty.
A certificate is issued for a specific lot. If a supplier holds three lots of a compound and shows one certificate, two thirds of their customers are receiving material the document does not describe. Ask for the batch reference on the certificate and check it against the vial when it arrives.
If those two numbers do not match, you have an uncharacterised compound, whatever the paperwork says.
3. What analytical method was used?
A purity figure without a method is a number without a meaning.
You want HPLC with a stated detection wavelength, and mass spectrometry for identity. Two different tests answering two different questions: how much of one thing is present, and what that thing is.
A certificate with only a purity figure and no identity confirmation is incomplete. A pure sample of the wrong compound produces an excellent purity number.
4. Is net peptide content available?
Most suppliers will not have this, and asking tells you something either way.
HPLC purity is a proportion of detected material. It excludes residual water, counterion and solvent, which together can be twenty percent or more of what is in the vial. Net peptide content is the measurement that captures actual peptide by mass.
A supplier who knows what you are asking and explains why they do or do not have it is running real analysis. One who does not recognise the term is reselling.
5. What happens to a batch that fails?
Ask it directly and listen to how quickly the answer comes.
The right answer is that it is rejected and not sold. The wrong answers are vague, or involve selling it at a lower purity grade, or blending it into another lot.
Every supplier has had a batch fail. What they did next is the useful information.
6. How is it shipped, and at what temperature?
A certificate describes material at the moment it was tested, in the laboratory that tested it. It says nothing about the journey to your bench, and that journey is where most real world degradation happens.
For cold chain compounds, ask what packaging is used and which days they ship. A supplier who dispatches frozen material on a Friday has not thought about where it spends the weekend.
7. What are the storage conditions for this specific compound?
Not for peptides generally. For this one.
Conditions vary considerably, and a supplier quoting one blanket instruction across their whole catalogue has not checked. NAD+ is refrigerated where most peptides are frozen. Glutathione oxidises on air exposure. L-Carnitine needs no cold chain at all.
If the storage line is identical on every product page, treat all of them as unverified.
8. Where is it sourced and what checks are applied on arrival?
Almost nobody synthesises their own catalogue. That is normal and not a problem in itself.
The question is whether the supplier tests on arrival or passes on the manufacturer’s paperwork. A certificate you did not commission is a certificate you are trusting rather than verifying, and there is a meaningful difference between a supplier who knows that and one who has not considered it.
9. What will they refuse to sell you?
This is the question that tells you the most and almost nobody asks it.
A supplier operating properly has a list of things they will not do. They will not advise on use in a person. They will not ship where a compound cannot lawfully be imported. They will decline an order where the intended use is clearly outside research.
A supplier with no such list is not being helpful. They are being indiscriminate, and indiscriminate suppliers attract regulatory attention that eventually reaches their customers’ order histories.
Warning signs
- Dosing or administration guidance on a research use only site. The two positions are incompatible and the site cannot hold both
- Identical purity figures across every product, usually 99 percent, with no method stated
- Before and after imagery, or testimonials describing effects in people
- Certificates shown as low resolution images with the batch reference illegible
- No physical address and no company registration number
- Claims of FDA approval or of pharmaceutical grade, neither of which means anything for a compound sold for research
What to do with the answers
Ask three or four of these by email before a first order. The reply speed and specificity tells you more than the website does.
Then verify one thing yourself when the parcel arrives: batch reference on the vial against batch reference on the certificate. Thirty seconds, and it catches the most common failure in the entire supply chain.
How we answer these
Certificates are published on the product page before purchase. They are issued per batch and the reference is recorded against your order. Purity is by HPLC with identity confirmed separately by mass spectrometry. A failed batch is rejected rather than sold. Cold chain items ship early in the week. Storage conditions are stated per compound, not per catalogue. And there is a written list of what we decline, which is on the research use policy page.
Net peptide content is the one we cannot always supply, and where it matters for your work you should ask before ordering rather than assume.