What the Peptigrity Purity Index measures
The index measures the recency-weighted average purity of research peptides that have been independently tested by third-party laboratories — currently 99.49 across 9,016 published HPLC results. It reflects the samples that were tested, not the market as a whole.
How the index is calculated
Each compound's index is the mean of its published HPLC purity results, weighted by recency: a test within 90 days counts at full weight, one within a year at 0.6, and older tests at 0.3. The composite is the test-count-weighted mean of those per-compound indices.
A compound is published only with at least 5 tests carrying a numeric purity. No single compound may exceed 15% of the composite weight, so a heavily tested compound cannot dominate the headline figure. Blend vials and net-content-only tests are excluded from compound averages.
Why a minimum of five tests is required
Five tests is the floor below which a single outlier moves the average more than the underlying quality does. A compound with one or two results — Adipotide, IGF-1 DES, EPO (Erythropoietin) — renders an em dash rather than a number, because a two-test “average” is a data point, not a measurement.
What counts as an acceptable purity level
95% is the research-grade purity bar and 98% is a strong result. Across the published set, 0.32% of tests fall below 95%, so most tested material clears the research-grade threshold — see peptide purity standards for the reasoning behind those cut-offs.
How the index differs from a vendor's own COA
A vendor's certificate reports one batch the vendor selected and paid to test; the index aggregates third-party results across many vendors and batches, with no vendor input into which samples are included. Because Peptigrity sells nothing and takes no vendor payment, no seller can influence the number that represents their compound.
Which compounds have enough data to be indexed
61 compounds currently meet the 5-test threshold, out of 64 with any published test. The full list, with each compound's index and 90-day change, is in the index by compound table above.
What the index does not measure
The index measures HPLC purity only. It does not measure endotoxin load, heavy-metal content, sterility, or batch-to-batch variance, and it is not a guarantee of any future batch. A high index means the tested samples were pure, not that every vial from every vendor will be.
How often the index updates
The index updates continuously as new certificates are submitted and approved; this page is regenerated hourly, and a nightly snapshot locks each day's figure so a citation dated to a given day stays reproducible.
How to cite the index
Attribution is free. Cite the composite with its date and sample size, and link to this page:
The Peptigrity Purity Index, Peptigrity, 2026-07-25. Composite 99.49 across 9,016 third-party HPLC tests. https://peptigrity.com/purity-index