Compound Quality
Sterile And Endotoxin-Free Are Two Different Findings. Most Certificates Only Test For One.
Sterility and endotoxin testing catch different things. A batch can pass one and never be checked on the other, and the word "sterile" alone does not tell you which.
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"Sterile" is one of the more reassuring words a label can carry. It is also one of the more misunderstood ones, because it only answers part of the question a research buyer actually cares about.
Sterility testing cultures a sample to confirm nothing is alive in it. No bacteria, no fungus, nothing growing. It is a biological test with a pass or fail outcome.
Endotoxin testing is a separate assay, usually run by the LAL method. Endotoxins are fragments left behind by certain bacteria, and they can survive the exact processes that killed the organism that produced them.
That means a batch can be genuinely sterile, in the sense that nothing in it is alive, and still carry a meaningful endotoxin load. Sterile is not a stand-in for endotoxin-free. They are two separate results.
Catalyst tests and reports both, separately.
Sterility and LAL endotoxin screening, as two distinct lines on the same certificate.
Visit Catalyst Biolabs →1Why the same process does not catch both
Sterilization methods are built to kill living organisms. Heat, filtration, and similar processes are effective at that job. Endotoxin, the leftover fragment of a bacterial cell wall, is not alive to begin with, so a process aimed at killing life does not necessarily remove it.
Killing the organism and removing what it left behind are not the same accomplishment.
2Why "third-party tested" does not settle it
A supplier can run sterility testing, publish a pass, and call the batch third-party tested without ever ordering an LAL endotoxin assay. Nothing on that label is false. It is just incomplete.
"Tested" is not the same claim as "tested for this specific thing."
3Why this test gets skipped
The LAL assay is its own line item, run separately from a standard sterility culture. A supplier has to specifically order it, on top of the tests they already run, for it to appear on the certificate at all.
A missing endotoxin line usually means the test was never ordered, not that the result was hidden.
Sample format, reflecting the fields Catalyst publishes on a Certificate of Analysis. Open a real, lot-specific certificate on Catalyst's own COA library.
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Check both lines yourself.
Sterility and endotoxin, reported separately, tied to the lot number on the vial.
Open Catalyst Biolabs →4How to check it in under a minute
- Two separate lines, not one. "Sterility" and "Endotoxin" should each appear on their own.
- A method named for the endotoxin line. LAL is the standard method; if none is named, be skeptical.
- A numeric result, not just "pass." Endotoxin is usually reported in EU/mg, a measured figure against a limit.
- The lot number matching your vial. Otherwise you are reading about a different batch.
| On the certificate | Catalyst Biolabs | Typical supplier |
|---|---|---|
| Sterility result | Reported | Sometimes reported |
| Endotoxin (LAL) | Reported, numeric | Often absent |
| Identity confirmation | LC-MS, same report | Often absent |
| Tied to your lot number | Published before order | Product-level, reused |
| Lookup you can run yourself | Public verification page | Email and wait |
5What actually arrives
- A vial with a lot number printed on it.
- A certificate carrying that same lot number.
- Sterility and endotoxin, as two separate results, not one combined claim.
- A signature from an accredited, independent U.S. laboratory.
Read both lines. Then decide.
Open any listing, read the certificate for that exact lot, and check sterility and endotoxin separately.
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Comments
Did not know these were separate tests until now. Assumed "sterile" covered everything.
Same. Checked an old certificate from another supplier, it said sterile with no endotoxin figure anywhere.
Pulled the Sermorelin certificate before ordering. Both lines were there with actual numbers, not just pass or fail.
The bacterial-fragment explanation made it click for me. Killing the organism and removing the fragment are different jobs.
Verified the lab's accreditation separately too, came back exactly as listed.
Ordering process was simple, certificate was posted before the package even arrived.