Methods
Why two “99% pure” reports are not describing the same thing
Purity is a ratio between detected peaks, not a mass balance. Understanding that difference explains most disagreements about peptide quality.
Veritide Research · 28 July 2026 · 4 min read
Purity figures of 98% or 99% appear across the research-peptide literature and documentation, attached to material characterised to very different standards. Both figures can be accurate at once, because purity does not mean what it is commonly taken to mean.
What HPLC purity measures
Reverse-phase HPLC separates the components of a sample and reports the main peak as a percentage of total detected peak area. It is a ratio between what the detector registered at a chosen wavelength — not a statement about how much of a container's contents are peptide.
What sits outside that number
- Residual water. Freeze-dried material can hold a meaningful percentage by weight, measured by Karl Fischer titration.
- Counter-ion. Standard purification usually leaves trifluoroacetate, which adds mass containing no peptide.
- Anything the detector does not register at the selected wavelength.
A sample reporting 99% by HPLC with 12% water content is correctly described as 99% pure by that method while containing appreciably less peptide by mass than a drier sample with the same headline figure. Both reports can be honest; only one of them, read alone, is informative.
The practical reading
Compare net peptide content where it is reported, and treat an absent water figure as missing information rather than a reassuring one. Analytical depth — number of purification passes, breadth of impurity profiling — is where documentation quality genuinely varies.
Compounds referenced
Reference profiles: mechanism, published evidence and UK regulatory status.
Reference materials mentioned here
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Sources
Published for research and educational reference only. Not medical advice. No dosing, administration or acquisition guidance is provided.
