Short, plain-English definitions of every term used across our sourcing and quality series — with links to the full explainers.
Every term you'll meet across our Sourcing & Quality guide, defined without jargon. Each links to the full explainer where relevant. For research and educational purposes only.
Amino acid — the individual building block of a peptide. Peptides are short chains of amino acids joined in a specific order.
Batch / lot number — a code identifying one specific production run. It's what lets you match a vial to its test results. No matching lot number, no real traceability.
Chromatogram — the graph an HPLC test produces. A tall clean main peak with few side peaks signals high purity. How to read one.
COA (Certificate of Analysis) — the lab document reporting a batch's purity, identity, and other test results. Only meaningful if batch-specific and verifiable. Full guide.
Endotoxin — a contaminant from bacterial cell walls. Critically, HPLC and mass spec cannot detect it — it needs its own test.
Fmoc — a common protecting-group chemistry used in modern peptide synthesis to control which part of an amino acid reacts.
HPLC (high-performance liquid chromatography) — the gold-standard purity test: what percentage of the sample is the target peptide. Explainer.
Identity testing — confirming the sample is the right molecule, done by mass spectrometry. Purity without identity is only half the answer.
ISO/IEC 17025 — an international quality standard for testing laboratories. A lab operating to it follows a recognized quality system.
LAL assay — the standard endotoxin test (Limulus Amebocyte Lysate). Where it fits in the stack.
Lyophilization — freeze-drying. Turns purified peptide into the stable white powder you receive in a vial.
Mass spectrometry (MS) — measures molecular weight to confirm a sample's identity. Catches bait-and-switch that purity testing misses.
Purity (%) — the share of the sample that is the target peptide. ≥98% is the common quality bar. Only meaningful with a chromatogram behind it.
Reconstitution — dissolving lyophilized powder into solution. The dissolved form is far less stable than dry powder. Handling guide.
Solid-phase peptide synthesis (SPPS) — the standard method of building a peptide link by link on a solid resin bead. How it works.
Third-party testing — analysis by an independent lab with no stake in the sale. The most credible quality signal. Why it matters.
Traceability — an unbroken chain linking a vial to its batch, its test results, and the date they were run.
Once you know what quality looks like, the next step is finding vendors that actually meet the bar. That is exactly what our rankings measure.
Last reviewed July 2026. By the Peptides Uncaged Research Team. For research and educational purposes only.
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