Peptide Research Glossary — Terms, Methods, and Abbreviations
A working vocabulary for reading a COA, interpreting an HPLC chromatogram, and evaluating peptide research specifications — at the level a first-time buyer needs.
A working vocabulary for reading a COA, interpreting an HPLC chromatogram, and evaluating peptide-research specifications. Terms are defined at the level a first-time buyer needs to understand verified lab data — not a textbook, not a buyer’s guide. Cross-references link to the articles that demonstrate each concept.
Analytical methods
HPLC — High-Performance Liquid Chromatography
The standard separation technique for measuring peptide purity. A small volume of dissolved sample is pushed through a packed column; components exit at different times and are detected by UV absorbance. The resulting plot — the chromatogram — shows a main peak (the target compound) and any smaller impurity peaks. Purity is reported as the main peak’s integrated area divided by total area. Every AMINOSWORK COA lists an HPLC purity value.
LC-MS/MS — Liquid Chromatography with Tandem Mass Spectrometry
The standard identity-confirmation technique. After HPLC separation, ionized fragments are measured across two mass-spectrometry stages. The result is a mass spectrum that must match the theoretical mass of the target peptide within tolerance. HPLC answers how pure; LC-MS/MS answers is it really this molecule. Freedom Diagnostics COAs use both.
LAL — Limulus Amebocyte Lysate
The horseshoe-crab-derived assay for bacterial endotoxin. A positive LAL result indicates gram-negative bacterial contamination at or above the detection threshold. AMINOSWORK currently runs LAL only on GLP-class compounds (GLP1-S, GLP2-T, GLP3-R, Cagrilintide) — never claimed as universal coverage across the catalog.
Retention Time (RT)
The number of minutes a compound takes to traverse the HPLC column. RT is a fingerprint of how the compound interacts with the stationary phase under given conditions. Two identical lots of the same peptide should produce peaks at the same RT within a narrow tolerance.
mAU — milli-Absorbance Units
The Y-axis unit on an HPLC chromatogram. Measures how much UV light (typically 220 nm) the flowing sample absorbs at each moment. Taller peaks = more absorbance = more compound at that RT. mAU is not a direct concentration unit; peak area (mAU × time) is what’s integrated for purity percentages.
Documentation
COA — Certificate of Analysis
The signed, dated report from the third-party lab documenting what was tested, how, and what was measured. A credible COA names the lab, names the method (HPLC, LC-MS/MS, LAL), gives the lot identifier, gives purity as a percentage, and shows the underlying chromatogram or mass spectrum. An AMINOSWORK COA can be scanned from the QR on the vial or opened from the batch verification page. Read the interpretation checklist.
Lot
A unique, traceable production identifier. Every AMINOSWORK vial carries a lot number matching exactly one Freedom Diagnostics COA. Lot numbers follow the pattern 2602-C###-<size>-<seq>, where the C### segment identifies the synthesis run and the numeric tail identifies the fill lot. Two vials with the same lot number came from the same analyzed batch.
Batch
In AMINOSWORK usage, interchangeable with lot: one synthesis-and-fill run, tested once, certified once. Other vendors sometimes distinguish synthesis batch from fill lot; AMINOSWORK does not — one COA per vial.
What a COA measures
Purity
The main-peak area divided by total integrated peak area on the HPLC chromatogram, expressed as a percentage. A purity of 99.50% means that 99.50% of detectable UV-absorbing material is the target peptide; the remaining 0.50% is detected but not characterized as the target. 99% is the internal floor for every AMINOSWORK lot. What % Purity Is Enough? →
Identity
Confirmation that the molecule in the vial is, in fact, the molecule on the label. Identity is established by mass spectrometry: the measured mass must match the theoretical mass of the peptide’s elemental formula within tolerance. A high-purity compound that fails identity is not the compound you ordered.
Endotoxin
Lipopolysaccharide contamination from gram-negative bacteria. Even at low levels, endotoxin is biologically active and can confound in-vitro or in-vivo assays. Measured in endotoxin units per mg (EU/mg) via LAL. AMINOSWORK publishes LAL values on GLP-class compound COAs.
Peak area
The integrated area beneath a chromatogram peak. Used to quantify relative amounts of compounds in a mixture. Purity percentages are ratios of peak areas, not peak heights.
Chromatogram
The graph output from a chromatographic separation: X-axis is retention time (minutes), Y-axis is detector response (mAU for UV detection). A well-resolved peptide chromatogram shows a dominant peak near the expected RT with minimal baseline noise. View an annotated reference chromatogram →
Compound identity
CAS number
Chemical Abstracts Service Registry Number. A globally unique numeric identifier for a specific chemical substance. Every AMINOSWORK compound profile lists a CAS when one has been assigned — a missing CAS is not automatically a red flag for novel or modified peptides (many lipidated GLP analogs have CAS numbers assigned years after publication).
PubChem CID
The NCBI PubChem Compound IDentifier. A numeric database key that links to structural data, InChI strings, 2D/3D representations, and cross-references to UniProt, DrugBank, and primary literature. AMINOSWORK compound profiles link out to PubChem wherever a CID exists; it is the single most authoritative free-access structural source.
Sequence
The amino-acid order of a peptide, written N-terminus to C-terminus. Expressed in either three-letter code (Gly-Glu-Pro) or one-letter code (GEP). Modifications (acetylation, amidation, non-natural residues) are annotated inline: Ac- prefix for acetyl, -NH₂ suffix for C-terminal amide, D- prefix for D-amino acids.
Molecular weight (MW)
The sum of atomic weights across the molecular formula, expressed in g/mol. Peptide MW is typically reported as the average mass (natural isotope distribution), not the monoisotopic mass. For identity confirmation, mass spectrometry compares the measured monoisotopic mass (a peak specifically of the most abundant isotope combination) against theoretical. A 1419.55 g/mol compound like BPC-157 gives a monoisotopic mass near 1418.74.
Handling
Lyophilized
Freeze-dried: sample frozen under vacuum so that water sublimates directly from solid to gas, leaving a dry peptide cake. Lyophilized peptides are the standard research-supply format because they are shelf-stable at −20 °C for years and tolerate international shipping without degradation.
Reconstituted
Dissolved in solvent. For most peptides, the solvent is sterile water, bacteriostatic water (water + 0.9% benzyl alcohol), or a buffered aqueous vehicle appropriate to the peptide’s solubility. Reconstituted peptides typically require refrigeration (2–8 °C) and have shorter stability than lyophilized material.
Regulatory framing
RUO — Research Use Only
A regulatory classification for reagents sold for in-vitro, analytical, or preclinical laboratory research only. Not a drug, not a supplement, not for human or veterinary administration. Every AMINOSWORK product ships under RUO framing. The classification is what the compound is sold as, not a statement about what it is chemically.
GLP — Good Laboratory Practice
A quality framework for non-clinical laboratory studies, primarily used to govern safety testing submitted to regulators. Within AMINOSWORK terminology, GLP-class compounds is a catalog shorthand for the higher-rigor subset (GLP-1S, GLP-2T, GLP-3R, Cagrilintide) that receive expanded analytical coverage including LAL endotoxin testing.