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Is underfilling common in research peptides?
The short answer
Quantity against label claim is the most frequently reported failure mode in public peptide testing datasets — more common than wrong identity. Much of it appears to be systematic rather than deliberate: filling by powder weight without correcting for counter-ion and moisture produces consistent under-delivery even from suppliers acting in good faith.
In detail
The distinction between systematic and deliberate is useful because the remedy differs. A supplier correcting for net peptide content fixes it permanently; a supplier who cannot explain their filling basis probably has not thought about it.
It also explains why identity-only testing gives false comfort. Confirming that a vial contains the right peptide says nothing about how much.
Because failures like these only inform the market when they are visible, we publish every result we produce, including the ones that fail.
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