Glossary

Plain-English definitions of the terms used across pepmg — the pricing math and the lab-testing vocabulary. These are definitions only. Nothing here is medical, dosing, or human-use guidance; everything on pepmg is for research use only.

▸ Price metrics

$/mg: Two vials at the same sticker price are not equal if one holds more compound. pepmg converts every listing to price per milligram, so a 5 mg and a 10 mg vial can be compared on one scale. It is the single number every pepmg ranking sorts by.
spread: A spread of 3× means the most expensive vendor charges three times the cheapest for the same milligram of the same compound. Large spreads are the whole reason comparing pays.
median: The median $/mg is a more honest “typical price” than an average, because one unusually cheap or expensive listing cannot drag it around the way it drags a mean.

▸ Testing & analysis

COA: A COA is the document a testing lab issues for a specific batch, reporting what the material is and how pure it measured. pepmg tracks whether a vendor publishes COAs and who tested them; it does not verify or vouch for the results.
HPLC: HPLC pushes a dissolved sample through a column so its components come out separately and can be measured. On a peptide COA it is the usual method behind a stated purity percentage.
mass spectrometry: Mass spectrometry weighs molecules very precisely, which helps confirm that a sample is the compound it claims to be. It is frequently paired with HPLC on a COA.
purity: A purity of 99% means testing found the sample to be 99% the intended compound and 1% other material. Purity is measured by a lab (commonly via HPLC) and stated on the COA for that batch.
lyophilized: Lyophilization (freeze-drying) removes water from a frozen material under vacuum, leaving a dry powder that stores and ships more stably than a liquid. Most research peptides arrive lyophilized.
third-party testing: A result carries more weight when the lab that produced it has no stake in the sale. pepmg notes whether a COA was issued by an independent testing lab versus the vendor itself.
domain age: pepmg reads each vendor's domain registration date (public WHOIS/RDAP) and the first time the Wayback Machine archived the site, and shows the earlier of the two as a rough “online since.” Longevity is a weak but objective trust signal — outright scam shops rarely last long — but an aged domain can be bought or a brand rebranded, so treat it as one data point, not proof of trustworthiness. It's reported as a longevity signal on the vendor page and is not scored into the Vendor Score, so a newer vendor is never penalized for it.

▸ Lab & handling

aliquot: An aliquot is one measured sub-portion taken from a larger amount — for example, splitting a stock into several equal, smaller measures for separate handling. It is a general laboratory and chemistry term, not specific to any one material.
vial: Research peptides are typically supplied in small sealed glass vials, often holding a freeze-dried powder. Vial size — the milligrams it contains — is what pepmg divides price by to get $/mg.
reconstitution: Reconstitution means adding a liquid (a diluent) to a lyophilized powder so it dissolves and can be measured by volume. pepmg's calculator does the concentration arithmetic as a reference for laboratory handling only — it is not preparation or administration guidance for human use.
bacteriostatic water: Bacteriostatic water is sterile water containing roughly 0.9% benzyl alcohol, which inhibits the growth of bacteria. It is a common solvent in laboratory settings. This is a definition of the substance, not guidance to prepare or use any material.
net peptide content: A vial's labeled milligrams may include non-peptide mass (salts, residual water, counter-ions). Net peptide content is the peptide portion itself. When it is known it is the most honest basis for $/mg, though vendors rarely publish it.

▸ Regulatory

RUO: Research Use Only means a product is intended for laboratory research, not for consumption or medical use. pepmg is a price index for RUO materials and provides no medical or human-use guidance.
CAS number: A CAS Registry Number is a unique identifier for a specific chemical substance, used to look it up unambiguously across databases regardless of the name a seller uses.

All products listed are sold by third-party vendors for laboratory and research use only (RUO). Where an FDA label or a peer-reviewed study has published a dose, pepmg reports it with the source named, because that is safer than guessing. It is a report, not medical advice and not a recommendation to use anything. pepmg sells nothing and ships nothing. Listings are price-tracking data, not endorsements.