Peptide Purity vs Sterility vs Endotoxin: What's the Difference?
“Purity, sterility and endotoxin are three separate quality checks, and a peptide can pass one while failing another. This guide explains what each test measures, how they differ, and why a Certificate of Analysis should report them separately.”
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Scientific Research Overview
Abstract & Executive Summary
Three words appear again and again on research peptide quality documents: purity, sterility and endotoxin. They are often treated as if they mean the same thing. They do not. Each one is measured with a different method and answers a different question.
Three tests, three questions Purity -> Is it the right peptide, without impurities? Sterility -> Are there any living microbes? Endotoxin -> Are there bacterial fragments left behind?
1. Purity: A Chemical Question
Purity is measured by reversed-phase HPLC. It shows how much of the peptide material is the target sequence compared with related impurities such as deletion or truncated sequences.
2. Sterility: Are Living Microbes Present?
A sterility test checks whether viable bacteria or fungi are present. Samples are placed in growth media and incubated, usually for 14 days, and then checked for growth.
3. Endotoxin: What Bacteria Leave Behind
Endotoxins are lipopolysaccharides from the outer membrane of Gram-negative bacteria. They remain even after the bacteria themselves are killed or filtered out.
Mechanism of Action
Why They Must Be Reported Separately
Each test covers a gap the others leave open:
Reading Them on a COA
Common Misunderstandings
Every Geno Bio Canada batch can be checked by lot number on the Certificates page. Related reading: How Peptides Are Tested.
Geno Bio Canada products are sold for laboratory research use only and are not for human or animal consumption.
Key Study Highlights
Purity is chemical
HPLC purity measures the target peptide, not microbes.
Sterility is pass or fail
It checks for living bacteria and fungi.
Endotoxin is separate
Bacterial fragments can remain even in sterile material.
Three separate results
A complete COA reports each one on its own.
Scientific FAQs
References
- U.S. Food and Drug Administration (2012).Pyrogen and Endotoxins Testing: Questions and AnswersFDA Guidance for Industry
- U.S. Food and Drug Administration (2004).Sterile Drug Products Produced by Aseptic Processing: Current Good Manufacturing PracticeFDA Guidance for Industry
- United States Pharmacopeia (2022).Harmonized Standard: General Chapter 621 ChromatographyUSP Notice of Adoption
Procure Research Reference Materials
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