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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.
▸ 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 dosing 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, dosing, 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). pepmg sells nothing, ships nothing, and gives no medical, dosing, or human-use guidance. Listings are price-tracking data, not endorsements.