Beyond Purity: Endotoxin, Sterility and Heavy Metals
A certificate reporting identity and purity has answered two questions: is this the compound it claims to be, and how much of what’s detected is that compound versus byproducts of synthesis. It has not addressed three other categories of contamination that are chemically and biologically unrelated to purity and require entirely separate tests to detect. This article covers what each of those three tests actually checks for, and why an identity-and-purity-only certificate — the most common kind in circulation — is a partial picture rather than a complete one.
Why Purity Alone Doesn’t Cover This Ground
HPLC purity testing and the three tests below are answering completely different questions with completely different instruments. A sample can score extremely well on HPLC purity and still carry contamination that an HPLC run was never designed to detect, because the contamination in question isn’t a synthesis byproduct of the target molecule — it’s something else entirely, introduced by raw materials, water, glassware, or the manufacturing environment.
Heavy Metals Testing
What it is: Analysis (typically by ICP-MS, inductively coupled plasma mass spectrometry) for trace metal contamination — commonly lead, arsenic, cadmium, and mercury.
What it catches: Metal residues that can enter a batch from raw materials, reagents used during synthesis, or equipment, independent of how pure the target compound itself is by HPLC.
Typical add-on cost: Roughly $105 per test, on top of the base identity/purity panel.
Endotoxin Testing
What it is: A test (commonly the LAL — Limulus Amebocyte Lysate — assay) for bacterial endotoxin, a byproduct of certain bacterial cell walls that can persist even after the bacteria that produced it are no longer present or viable.
What it catches: Endotoxin contamination introduced during manufacturing, handling, or from water sources used in production — a completely different category from the synthesis-related impurities an HPLC purity result addresses.
Typical add-on cost: Roughly $180 per test.
Sterility Testing
What it is: A microbiological test, typically involving culturing a sample under conditions favorable to microbial growth over an extended period, to check for the presence of living bacteria or fungi.
What it catches: Live microbial contamination. This is a slower, more involved test than an instrument-based analysis like HPLC, because it requires giving any contaminating organisms time to actually grow and become detectable rather than an instant readout.
Typical add-on cost: Roughly $290 per test.
Also Worth Knowing: Fentanyl Screening
Some labs now offer a fentanyl screen as a standalone add-on, reflecting broader concerns about contamination risk across the research chemical supply chain generally, unrelated to any specific peptide chemistry. Typical add-on cost is roughly $75 per test. Like the three tests above, this is a separate check from identity/purity and won’t appear on a certificate unless it was specifically ordered.
Why Most Certificates Skip These
The base identity-and-purity panel from a reputable lab already runs in a real price range — Janoshik Analytical, a widely used lab in this space, prices in the roughly $215–450 range per test depending on the panel ordered. Each of the four additional tests above stacks on top of that base cost. A vendor publishing only identity and purity results isn’t necessarily hiding anything — cost is a completely legitimate reason a batch wasn’t run through the full panel, and full-panel testing on every single batch would meaningfully change the economics of the product.
That said, from a reader’s perspective, the practical takeaway is straightforward: an identity-and-purity-only certificate has covered two of at least five relevant categories. It’s a real and useful document, but it’s not a complete quality picture, and it shouldn’t be read as one. A certificate that includes heavy metals, endotoxin, and/or sterility results alongside identity and purity is meaningfully more complete than one that doesn’t — not because the shorter certificate is dishonest, but because it’s answering fewer questions.
Where Kinotype Stands Today
Full disclosure on our own testing, since this article is about what a purity-only certificate leaves out: right now, none of our eighteen products carry a certificate that includes any of the four tests above. Nine products show testing in progress and haven’t been tested for anything yet, purity included. The other nine show certificate under review — a legacy certificate exists, but we’re re-verifying it with the lab, and until that’s resolved we’re not asserting what panel it does or doesn’t cover.
Heavy metals, endotoxin and sterility testing are meaningfully more expensive than a base identity/purity panel, for the real reasons explained above — that’s as true for us as for anyone else in this category, and we’re not going to pretend a full panel on every batch is a smaller lift than it is. What we can commit to is disclosure: when a certificate is issued for a given lot, its entry on the certificates of analysis page will state exactly which of these tests were run, not just whether a certificate exists.