What 98% Purity by HPLC Actually Means
"98% pure by HPLC" appears on nearly every research peptide listing. Here is what that figure measures, what it does not, and how to read it critically.
Purity by HPLC is the most commonly quoted quality metric for research peptides. It is genuinely useful — but it is also frequently misunderstood. Knowing exactly what it measures helps you compare suppliers on a real basis instead of a marketing one.
How the percentage is measured
HPLC pushes a dissolved sample through a column that separates its components by how they interact with the column material. A detector records each component as a peak. The area under the target peptide’s peak, divided by the total area of all peaks, gives the purity percentage. So "98% purity" means the target peptide accounts for 98% of the detected material.
What the other 2% is
The remaining percentage is made up of impurities — typically truncated sequences, deletion products, or by-products from synthesis. For most research applications, a small, well-characterized impurity fraction is acceptable. What matters is that it is measured and disclosed rather than hidden.
Purity is relative to what the detector sees. A clean-looking number still depends on a properly run method and an attached chromatogram you can actually inspect.
Purity is not the same as identity
This is the key point researchers miss: HPLC purity tells you how clean a sample is, not whether it is the correct molecule. A sample could be 99% pure and still be the wrong peptide. That is why a complete COA pairs HPLC with mass spectrometry — purity plus identity together.
How to read a purity claim critically
- Ask whether a chromatogram is provided, not just a number
- Check that the figure is tied to your specific batch
- Confirm identity separately via mass spectrometry
- Be skeptical of round, suspiciously perfect numbers with no documentation
This article is provided for laboratory and in-vitro research context only. Pulse Peptide Labs products are not for human consumption, diagnostic, therapeutic, or medical use, and nothing here is medical advice.
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