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Why does my CoA not mention water content?
The short answer
Because water determination is a separate analysis — typically Karl Fischer titration — and is not part of a standard purity and quantification test. Reverse-phase HPLC with UV detection does not see water at all. A certificate that stays silent on moisture is being accurate about its scope; one that implies it measured moisture without running it is not.
In detail
Lyophilised peptides are hygroscopic and pick up water from the air, especially in vials that have been opened or shipped through humid conditions. That water adds weight without adding peptide.
Quantification against a reference standard sidesteps the problem for most practical purposes: it measures the peptide directly, so moisture does not inflate the result the way weighing powder does.
Read a silent CoA as scope, not evasion — and read stated limits as a positive signal. Our reports name what the method does not cover rather than leaving you to assume.
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