The vocabulary behind the certificates.
Certificates, registry records and research papers lean on a working vocabulary they rarely stop to define. Each entry here defines one term in plain language — what it measures, what it does not, and where it is used across the guides and the research library.
Certificates & analytics
Certificate of analysis (COA)
A laboratory report tying one tested sample from one named batch to a set of measured results — typically identity and purity — issued on a stated date by a named laboratory.
Read the definitionHPLC purity
The area of a compound's chromatographic peak as a percentage of all detected peak area — a relative measure of what the detector saw, not a statement of how much of the powder is peptide by mass.
Read the definitionMass spectrometry identity
An identity check that measures a molecule's mass and compares it with the value calculated from the intended sequence — answering whether the right molecule is present, not how much of it there is.
Read the definitionNet peptide content
The fraction of a lyophilised powder's mass that is actually peptide, after subtracting residual water and counterion — a different measurement from chromatographic purity, and reported far less often.
Read the definitionEndotoxin
Lipopolysaccharide fragments from the outer membrane of Gram-negative bacteria — heat-stable, biologically potent contaminants that chemical purity tests do not detect, measured by the LAL assay.
Read the definitionKarl Fischer water content
A titration method that measures the water remaining in a lyophilised powder — one of the reasons gross powder mass overstates the peptide a vial actually contains.
Read the definitionBatch or lot number
The identifier tying a vial to one specific synthesis run — the link that lets a certificate describe the material actually in hand rather than material in general.
Read the definitionPurity vs quantity
Two independent claims that are routinely conflated: purity describes the quality of the compound present, quantity describes how much of it there is — and a certificate can establish one without the other.
Read the definitionReference standard
A characterised sample of known identity and purity against which an analytical method compares the material under test — the anchor that turns an instrument reading into a result.
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Chemistry & identity
TFA salt vs acetate salt
The two counterion forms in which synthetic peptides are commonly supplied — a purification leftover that changes the powder's mass and properties without changing the peptide itself.
Read the definitionCounterion
The oppositely charged ion that accompanies a charged peptide in its solid form — part of the powder's weight, but not part of the peptide.
Read the definitionFree base vs salt mass
Two ways of stating a compound's mass — with or without its counterion — which is why a registry's molecular weight and a vial's contents are not the same figure.
Read the definitionLyophilisation
Freeze-drying: removing water from a frozen solution by sublimation under vacuum, leaving the stable solid cake or powder in which peptides are shipped and stored.
Read the definitionPeptide sequence
The ordered chain of amino-acid residues that defines a peptide — the compound's actual identity, from which its formula, mass and behaviour follow.
Read the definitionMolecular weight vs formula weight
The mass of one molecule, computed from its formula — with the caveat that registry values describe the free base, while the material in a vial is a salt with residual water.
Read the definitionCAS number
A unique registry number assigned to a chemical substance by the Chemical Abstracts Service — the most widely used identifier for matching a compound across suppliers and literature.
Read the definitionUNII
A Unique Ingredient Identifier from the FDA's Global Substance Registration System — a free, public, molecular-structure-based code identifying one substance form unambiguously.
Read the definitionPubChem CID
The compound identifier in PubChem, NIH's open chemistry database — the record from which structure, formula and computed molecular weight can be read for free.
Read the definitionInChIKey
A fixed-length hashed form of the IUPAC InChI structure identifier — 27 characters that make one chemical structure searchable and comparable across databases.
Read the definitionCompound synonyms and aliases
The multiple names — codes, trade names, sequence names — under which one compound circulates, and the reason registry identifiers rather than names settle identity.
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Handling & storage
Bacteriostatic water vs sterile water
Two reconstitution diluents that differ by one ingredient — 0.9% benzyl alcohol — which inhibits bacterial growth in an opened vial and defines how long a reconstituted solution can be held.
Read the definitionReconstitution
Returning a lyophilised solid to solution by adding a measured volume of diluent — the step that fixes the solution's concentration and restarts the stability clock.
Read the definitionStorage stability
How well a compound retains its identity and purity over time under stated conditions — a property of temperature, moisture, light and form, not a single shelf-life number.
Read the definitionCold chain
An unbroken sequence of temperature-controlled storage and transport from producer to end point — required for inherently unstable biologics, and distinct from the ambient shipping that stable lyophilised solids tolerate.
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Regulatory & evidence
503A vs 503B
Two sections of the US Food, Drug and Cosmetic Act governing drug compounding — traditional patient-specific pharmacies under 503A, larger outsourcing facilities under 503B — that set which substances compounders may use.
Read the definitionResearch use only (RUO)
A supply category for laboratory research materials that are not drugs, foods or devices — sold without approval for, and with the express exclusion of, human or veterinary use.
Read the definitionGMP
Good Manufacturing Practice: the quality-system regulations governing pharmaceutical production — process controls and documentation that batch testing alone does not replicate.
Read the definitionPMID and DOI
The two identifiers that pin a scientific claim to a checkable source: PubMed's record number for a paper, and the persistent digital object identifier its publisher registers.
Read the definitionEvidence tiers
The ladder from cell studies to animal work to human trials — a grading of how directly a piece of research bears on questions about people, and the reason a study count alone says little.
Read the definitionPeer review
Pre-publication scrutiny of a manuscript by independent researchers in the field — a filter for obvious flaws, not a guarantee that a paper's findings are correct.
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