Research peptides · Glossary
Research peptide glossary
Definitions of the analytical, literature and regulatory terms used across the Veridian Research reference library, from HPLC purity and mass spectrometry to research-use-only status.
- Certificate of analysis (CoA)
- A certificate of analysis is a laboratory report of the tests performed on one batch of material, listing each test, its method, the result and the test date. It documents only the tests printed on it.
- Batch (lot) number
- A batch or lot number is the identifier for material made in a single production run. It links a vial to the certificate of analysis for that run; results from one batch do not describe another.
- HPLC
- High-performance liquid chromatography (HPLC) is an analytical technique that separates the components of a sample by pumping it through a packed column and detecting each component as it elutes. Reverse-phase HPLC with UV detection is the standard purity method for synthetic peptides.
- HPLC purity
- HPLC purity is the main peptide peak's share of the total detected peak area, expressed as a percentage. It is a relative measure of the detected components, not the amount of peptide in a vial, and it does not count impurities the detector cannot see.
- Mass spectrometry (MS, LC-MS)
- Mass spectrometry measures the mass-to-charge ratio of ionised molecules. In peptide testing it confirms identity: that the main component has the molecular mass expected for the named sequence. LC-MS couples liquid chromatography to a mass spectrometer.
- Peptide content (net peptide content)
- Peptide content is the percentage of a lyophilized powder's weight that is the peptide itself, the rest being water, counter-ions and salts. It is measured separately from purity, typically by amino acid analysis or nitrogen determination.
- Counter-ion (TFA salt, acetate salt)
- A counter-ion is the oppositely charged ion that pairs with a peptide's charged groups in the solid form. Peptides purified with trifluoroacetic acid are usually isolated as TFA salts; an acetate salt results from an exchange step. The counter-ion contributes to the powder's weight.
- Endotoxin
- Endotoxin is lipopolysaccharide from the outer membrane of Gram-negative bacteria, a common contaminant that can interfere with cell-based experiments. It is measured by the Limulus amebocyte lysate (LAL) assay and is not detected by an HPLC purity test.
- Lyophilization
- Lyophilization, or freeze-drying, removes water from a frozen solution by sublimation under vacuum. Peptides are supplied lyophilized because the dry powder is far more chemically stable in storage and transit than a solution.
- Molecular weight (Da)
- Molecular weight is the mass of one molecule, expressed in daltons (Da) or grams per mole. For a peptide it is the sum of its amino acid residues and modifications, and it is the value mass spectrometry checks against.
- CAS registry number
- A CAS registry number is a unique identifier assigned by the Chemical Abstracts Service to a specific chemical substance. It lets a compound be identified unambiguously across suppliers, databases and literature regardless of its trade or code name.
- PubChem CID
- A PubChem CID is the compound identifier in PubChem, the open chemistry database run by the US National Center for Biotechnology Information. It links a structure to its properties, synonyms and related literature.
- PMID
- A PMID is the unique identifier of a record in PubMed, the US National Library of Medicine's index of biomedical literature. A citation with a PMID can be checked against the exact paper it claims to cite.
- DOI
- A digital object identifier (DOI) is a persistent identifier for a published work. Resolving a DOI at doi.org leads to the publisher's record of the paper regardless of where it is hosted.
- In vitro
- In vitro describes experiments performed outside a living organism, such as in cell cultures or with isolated proteins. In vitro results show what a compound can do in a controlled system, not what it does in a whole organism.
- In vivo / preclinical
- Preclinical research is laboratory and animal work done before, or without, testing in humans. In vivo preclinical studies use living animals, most often rodents; their results frequently fail to carry over to humans.
- Clinical trial phases
- Clinical trials test a compound in humans in phases: Phase 1 assesses safety and pharmacokinetics in small groups, Phase 2 explores effects and dosing in a larger group, and Phase 3 compares the compound against placebo or standard care in large populations.
- Half-life
- Half-life is the time taken for the concentration of a compound to fall by half. It is a property measured in a particular system, such as plasma in a given species, and differs between in vitro and in vivo settings.
- Agonist
- An agonist is a molecule that binds a receptor and activates it. A dual or triple agonist activates two or three receptor types with a single molecule.
- Research use only (RUO)
- Research use only (RUO) labels a material supplied for laboratory research. An RUO material is not approved by the FDA or any regulator for human or veterinary use, diagnosis or treatment.
See these terms applied in how to read a certificate of analysis.
Last reviewed 2026-10-01.