Question 1

How can I tell whether a peptide or supplier is trustworthy?

Accepted Answer

Look at what is verifiable, not at the tone of the website. A serious supplier publishes the certificate of analysis for the exact batch they sell you, names the lab that ran it, explains shipping and storage, and makes no clinical promises. If the COA does not match your vial's batch number, it is not your COA.

Question 2

What is a COA and what should I actually look at in it?

Accepted Answer

A COA is a lab report with the results of tests run on a sample represented as coming from a batch. Reading one well reduces risk, but it does not validate the product: a matching lot number improves traceability, it does not prove chain of custody, and a PDF may not be authentic. This is document literacy, not a guarantee that an unapproved product is safe.

Question 3

Where can I learn to buy peptides with better judgment and less marketing?

Accepted Answer

Start by understanding what the product label means, then how to read a COA, then supplier criteria. With that you compare traceability instead of discounts. On Péptidos Fácil, the where-to-buy guide and the research-use page cover that groundwork without selling anything.

Question 4

What does it actually mean when a peptide is sold as '99% pure'?

Accepted Answer

That figure normally comes from an HPLC analysis and describes what share of the detected material sits under the main peak. It does not tell you how much product is in the vial, whether the sequence is correct, or whether it is sterile or endotoxin-free. High purity and a suitable product are two different claims.

Question 5

Does a certificate of analysis prove a product is sterile and endotoxin-free?

Accepted Answer

No — unless the certificate explicitly includes those tests. Sterility and bacterial endotoxins are measured by specific assays, separate from purity or identity. Most 'research' peptide COAs cover only identity and purity, so the absence of microbial contamination simply has not been demonstrated.

Question 6

What should a vial label tell me, and what stability signs can I actually look for?

Accepted Answer

A useful label identifies the compound, the stated amount, a batch number and a date, and lets you find the COA for that exact batch. On stability, the sensible rule is to follow the manufacturer's instructions for that specific product, and to distrust a vial that looks wrong: melted or caked powder, cloudy liquid, particles, or a damaged seal.

Question 7

On a COA, what is the difference between identity, content and purity?

Accepted Answer

They are three separate questions. Identity: is this the molecule it claims to be? Confirmed by mass spectrometry. Content or assay: how much material is in the vial? Purity: what share of the detected material is the main compound? A certificate can answer one and stay silent on the other two.

Question 8

What does a vial's batch or lot number actually prove?

Accepted Answer

A batch number identifies one specific production run and lets you link your vial to a certificate and a record. That is traceability, not quality: a batch can be perfectly labelled and still not have been properly tested. What is useful is that the batch on the vial matches the batch on the certificate you are shown.

Buying, quality and COA

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