This glossary defines 58 terms you'll see on research peptide COAs, vendor sites and regulatory news, in plain English. Each entry is one to three sentences, with a source where it states a fact about the outside world and a link to our longer guide where one exists. Terms are grouped A-Z, with numbered terms (503A, 503B) at the end.
Notice: Research peptides are sold for in-vitro laboratory research only. They are not FDA-approved, not for human or animal consumption, and this page is not medical advice.
A
Acetate salt. A peptide supplied with acetate as its counter-ion instead of trifluoroacetate. Contract manufacturer AmbioPharm says "the vast majority of peptide APIs are produced as acetate salts." See TFA salt, below.
Amino acid analysis (AAA). A lab method that breaks a peptide into its amino acids and measures them. It's one of the standard ways to measure net peptide content (Iris Biotech).
API (active pharmaceutical ingredient). The bulk substance that makes a drug work, before it's formulated. FDA's Import Alert 66-80 targets imported GLP-1 APIs.
B
BAC water (bacteriostatic water). Sterile water containing a preservative, typically 0.9% benzyl alcohol, packaged in multiple-dose vials. The FDA-approved label carries a "NOT FOR USE IN NEONATES" warning because of the benzyl alcohol (DailyMed). Compare bacteriostatic vs sterile water.
Batch number. See Lot number.
C
Category 1. Under FDA's interim policy for pharmacy compounding, nominated bulk substances FDA "does not intend to take action against" compounders for using, if conditions are met (FDA). It isn't drug approval.
Category 2. Nominated bulk substances with identified safety concerns; FDA "would consider taking action against a compounder" using them. FDA removed 12 peptides from Category 2 in April 2026 after nominations were withdrawn (details).
Category 3. Nominated substances with insufficient supporting information, also not covered by the Category 1 policy (FDA).
CGMP (current good manufacturing practice). FDA's manufacturing quality rules. Outsourcing facilities under section 503B must follow them; traditional 503A pharmacies generally don't (FDA).
Chromatogram. The graph an HPLC run produces: detector signal over time, with each peak representing a component. See HPLC purity explained.
COA (certificate of analysis). A lab report stating what was tested, how and with what result. A useful one names the lab, the lot and the test date. See how to read a peptide COA and our COA checklist.
Code-named product. A product sold under an abbreviation instead of its compound name. FDA's August 2026 letter to Peptide Partners identified names like "GLP-3 Reta" as specific drugs anyway (FDA).
Counter-ion. An ion bound to a charged peptide to balance it, usually trifluoroacetate or acetate. Counter-ions add weight, which lowers net peptide content (AAPPTEC).
D
Deletion sequence. A synthesis error in which one or more amino acids are missing. AAPPTEC lists deletions among the most common peptide impurities.
DWPE (detention without physical examination). An FDA import tool that lets staff hold listed products at the border without opening them. It's the mechanism behind import alerts such as 66-41. See peptide shipping and customs.
E
Endotoxin. Lipopolysaccharides "found in the outer membrane of gram-negative bacteria." FDA notes they "are not removed by sterilizing or microbiological filters" (FDA).
EU (endotoxin unit). The unit endotoxin results are reported in. Finnrick's Accuracy focus standard fails a sample "above 40 EU/sample" (Finnrick).
F
Fill accuracy. How close the measured peptide amount is to the label. Finnrick allows ±15% to ±35% depending on the standard (methodology).
Finnrick. An independent program that has peptide samples, mostly customer-bought, tested at partner labs and publishes vendor ratings. See what is Finnrick.
H
HPLC (high-performance liquid chromatography). The standard method for measuring peptide purity. It separates components on a column and reports the main peak's share of total peak area. See HPLC purity explained.
I
Identity test. A test confirming the substance is the one claimed, usually by mass spectrometry. Purity without identity doesn't prove what's in the vial.
Import alert. FDA guidance telling field staff which imported products may be detained. See peptide shipping and customs.
Intended use. The legal test FDA applies to decide whether a product is a drug, judged from how it's marketed. FDA's 2026 warning letters rely on it (Gram Peptides letter).
IU (international unit). A unit of biological activity rather than mass. Converting IU to mg needs a substance-specific factor. See mg, mcg and IU conversion and our unit converter.
J
Janoshik. An analytical lab that tests mailed-in samples and issues reports verifiable on its site with a task number and unique key (Janoshik). See how to verify a Janoshik report.
L
LAL (Limulus Amebocyte Lysate) test. The standard endotoxin assay, run in gel-clot, turbidimetric, colorimetric or chromogenic formats (FDA).
LC-MS. Liquid chromatography coupled to mass spectrometry. It separates components and measures their masses in one run.
Lot number. The code identifying one production batch. A COA is only useful for your vial if its lot number matches the one printed on the vial.
Lyophilized. Freeze-dried. FDA describes lyophilization as removing water from a frozen product under vacuum, "allowing the ice to change directly from solid to vapor" (FDA). See lyophilized peptides explained.
M
MALDI-TOF. A mass spectrometry technique used to measure peptide molecular weight (AltaBioscience).
Mass spectrometry (MS). A method that measures molecular mass. On a COA, it's how identity is confirmed.
mg / mcg. Milligram and microgram; 1 mg equals 1,000 mcg. Our reconstitution calculator handles the unit math.
N
Net peptide content (NPC). The share of a powder's total weight that is peptide, after water, solvents and counter-ions. AmbioPharm puts it at typically 60-90%.
Notice of FDA Action. The letter FDA sends when it detains an import, marked "Detained" or "Detained/[May be Destroyed]" on mail shipments (FDA).
P
PCAC (Pharmacy Compounding Advisory Committee). FDA's advisory panel on compounding substances. It met July 23-24, 2026, on seven peptides; its votes are non-binding (FDA).
Peptide. A short chain of amino acids, typically 2 to 50 (NHGRI). Under FDA's 2020 rule, a chain of more than 40 amino acids is a protein (Federal Register).
Purity. On a COA, usually HPLC purity: the main peak's area as a share of all peak areas. It isn't identity or quantity.
R
Reconstitution. Dissolving a lyophilized powder in a liquid for lab use. The concentration is simple division: mg in the vial over mL added. See how to reconstitute peptides.
Red List. The list of firms and products named in an FDA import alert for detention without examination (Import Alert 66-41).
Retention time. How long a component takes to come off the HPLC column. The main peak's retention time should be consistent for the same method.
RUO (research use only). A label saying a product is for laboratory research. FDA's 2026 letters say it doesn't protect a seller whose marketing shows human use (details).
S
Salt form. Which counter-ion a peptide carries, such as TFA, acetate or hydrochloride. It affects weight and can affect lab assays.
Sterile water. Water for injection with no preservative. The bacteriostatic water label directs that only preservative-free sterile water be used for neonates (DailyMed).
Sterility test (USP <71>). A test for viable microorganisms. It's separate from the endotoxin test, and few research-peptide COAs include it.
T
Task number. The number Janoshik assigns to each test, used with a unique key to verify a report.
TFA salt (trifluoroacetate). The counter-ion left by HPLC purification with trifluoroacetic acid. A 1999 study found TFA reduced cell proliferation in some cultures, which is why some labs exchange it for acetate or chloride.
Third-party testing. Testing by a lab independent of the seller. It's stronger when the lab is named and the report can be verified. See third-party tested peptides.
Truncated sequence. A peptide chain that stopped short during synthesis, a common impurity (AltaBioscience).
U
U-100. A concentration of 100 units per mL. MedlinePlus notes that standard insulin is U-100 and that "the type of insulin should match the type of syringe" (MedlinePlus).
U-40. A concentration of 40 units per mL. A U-40 syringe's unit markings correspond to different volumes than a U-100 syringe's. See U-40 vs U-100 syringes.
Unique key. The alphanumeric, case-sensitive code on a Janoshik report used to verify it.
USP (United States Pharmacopeia). The organization that publishes official drug quality standards, including chapters <85> (bacterial endotoxins) and <71> (sterility), which FDA guidance references (FDA).
W
WADA S0. The World Anti-Doping Agency's category for non-approved substances, banned at all times. BPC-157 has been named as an S0 example since the 2022 list. See the WADA Prohibited List.
WADA S2. The category for peptide hormones, growth factors and mimetics, including growth hormone-releasing peptides, per a BSCG summary of the 2026 list.
Warning letter. FDA's formal notice to a company that it considers to be violating the law. Letters are public in FDA's warning letter database. See our regulatory news tracker.
0-9
503A. The section of the FD&C Act covering traditional pharmacy compounding, which requires "valid patient-specific prescriptions" (FDA).
503A bulks list. FDA's list of bulk substances pharmacies may use in compounding when there's no USP monograph or approved-drug component (FDA). Adding a peptide requires rulemaking.
503B. The section covering outsourcing facilities, which can compound without patient-specific prescriptions but must follow CGMP and face FDA inspection (FDA).
Put the terms to work
Most of these terms come together on a single COA. Start with how to read a peptide COA, then compare vendors on the same criteria in best peptide vendors in the USA.
Two terms that often confuse readers get their own guides: TFA vs acetate salts and how long reconstituted peptides last.
Updated September 26, 2026. Sources are linked inline.