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How often should a vendor test their products?
The short answer
Per lot, at minimum. Peptide lots come from different syntheses and different filling runs, so a result from one lot does not transfer to the next. A vendor showing one certificate for a product line sold across many batches is showing you a snapshot, not a quality system — however good that snapshot is.
In detail
Lot-level testing is what makes a claim traceable: the certificate names a lot, the vial names the same lot, and the two can be matched.
Frequency also interacts with publication. Testing every lot but publishing selectively returns the picture to the same problem, because the visible subset is again chosen.
For buyers the practical check is simple. Find the lot number on your vial and ask for the certificate that names it.
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Iberian Analytical opens in Q1 2027 — €99 per test, 48–72 h target, and every result published in a public database, mandatory and free. Nothing is sold on this site today. Leave an email and we will write once, when the laboratory starts issuing certificates.
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