Freeze-drying never removes 100% of the water: some remains bound to the peptide molecules and counter-ions. It is usually measured by Karl Fischer titration, a water-specific technique, and expressed as a percentage of weight.
That water matters for two reasons. The first is chemical: degradation reactions such as deamidation or hydrolysis need water, so a powder with more moisture degrades faster. The second is about calculation: water has weight, and a high content lowers the percentage of real peptide in each milligram.
Freeze-dried powder is also hygroscopic: it absorbs moisture from the air. That is why vials must be kept closed and, if taken out of the cold, allowed to reach room temperature before opening so water does not condense on the contents.
A powder that looks sticky, collapsed or wet has absorbed water. It is a sign that its stability may be compromised, even if the original certificate was correct.
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Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).