Glossary
Peptide testing glossary
Plain, one- and two-sentence definitions of the terms PepIndex uses to evaluate research-peptide vendors — from certificate of analysis and assayed mass to coverage and provenance tiers. Each term links to itself, so any definition can be cited on its own.
- Certificate of analysis (COA)
- A document, usually issued by a testing laboratory, stating the measured properties of a specific lot of a product — most importantly its assayed purity and the identity of the compound. A COA is only as meaningful as the lab that issued it and whether its lot number matches the product you received.
- Assayed mass (actual mass)
- The mass of active compound a laboratory actually measured in a sample, as opposed to the mass printed on the label. When the assayed mass falls short of the labeled mass, the product is under-filled.
- Labeled mass
- The mass of compound a vendor states is in a vial, e.g. "10 mg". It is a claim until an assay confirms it.
- Label discrepancy
- The percentage gap between labeled mass and assayed mass. PepIndex computes this for every certificate record it holds; a large discrepancy means the vial contains materially less (or more) active compound than the label claims.
- Purity
- The share of a sample that is the intended compound rather than impurities, usually reported as a percentage on a certificate of analysis and typically measured by HPLC. High labeled purity is meaningless without a credible lab behind the figure.
- Lot (batch)
- A single production run of a product. Testing is only valid per lot: a certificate for one lot says nothing about a different lot, which is why lot numbers must match between the COA and the product.
- Lot-to-lot consistency
- How closely a vendor’s assayed purity and label accuracy hold from one production run to the next. Consistent results across lots indicate reproducible manufacturing; wide swings indicate the opposite.
- Third-party testing
- Analysis performed by an independent laboratory rather than by the vendor itself. A certificate from a named, recognised third-party lab is stronger evidence than one from an unnamed or in-house source.
- ISO/IEC 17025 accreditation
- The international standard for the competence of testing and calibration laboratories. A lab accredited to ISO/IEC 17025 has demonstrated it can produce technically valid results, which makes its certificates more trustworthy than those from an unaccredited lab.
- HPLC (high-performance liquid chromatography)
- The standard analytical method for measuring the purity of a peptide by separating its components. Most purity figures on a peptide certificate of analysis come from HPLC.
- Mass spectrometry (MS)
- An analytical method used to confirm a compound’s identity and molecular weight. Identity confirmation by MS complements the purity figure from HPLC.
- Reconstitution
- Dissolving a lyophilised (freeze-dried) peptide in a diluent to reach a target concentration. PepIndex provides a reconstitution calculator that is arithmetic only — it gives no dosing or protocol guidance.
- Research use only (RUO)
- A label indicating a product is sold for laboratory research and not for human or veterinary use, diagnostic purposes, or as a drug. Every vendor indexed by PepIndex labels its products this way.
- Score (PepIndex)
- A 0–100 figure computed for each vendor by the PepIndex Evidence Rubric from stored, sourced data points — never assigned by an editor. It measures what a vendor can demonstrate about its testing and business, not the quality of any substance.
- Coverage (PepIndex)
- The weighted share of scored fields PepIndex holds with a checkable source for a vendor. Coverage is published beside every score because a 90 built on four sourced fields and a 90 built on forty are different findings; a score is not interpretable without it.
- Provenance tier
- The status of a single data point: verified (a source was opened and confirmed), claimed (the vendor asserts it, uncorroborated), unsourced (no checkable source; earns no credit) or missing. A verified point earns full weight; a claim earns less; an unsourced value earns nothing.
- PepIndex Evidence Rubric
- The published formula that turns a vendor’s stored data points into its 0–100 score, weighting five criteria: testing transparency, documentation depth, track record, business transparency and commercial clarity. The full weights and worked examples are published on the methodology page.
Every figure behind these terms is published per vendor and per certificate. See the methodology for how the score and coverage are computed, or how to read a certificate of analysis.