How to Read a COA

Before any science, confirm this COA is about the vial in your hand. A COA that does not tie back to your exact lot number proves nothing about your vial.

• ·Lot or batch number — read it from the document and read it from the vial label. They must match character for character.
• ·Product / compound name, and the sequence or CAS number where applicable.
• ·Quantity per vial (e.g. 5 mg) and physical form (lyophilized powder, solution).
• ·Manufacture date, test date, and retest or expiry date.
• ·Storage conditions the batch was released under.
• ·Name and address of the testing laboratory — an independent third-party lab is stronger evidence than an in-house sheet.
• ·Analyst or authorized signatory, with a date and document/report number.
• ·Statement of intended use (research use only, API, or compounding-grade).

Purity means nothing until identity is proven — 99% pure something else is still the wrong compound. Look for the identity block near the top of the report.

• ·Mass spectrometry (MS / ESI-MS / MALDI-TOF) — observed molecular weight against the theoretical value. Check the observed weight is close to the published molecular weight of the compound, and that the raw spectrum is attached, not just a number.
• ·Amino acid sequence stated in single-letter code — compare it letter by letter to the published sequence.
• ·Appearance / colour description of the solid or solution.
• ·Solubility statement and recommended diluent.
• ·Optical rotation or NMR for small-molecule and non-peptide compounds.

Most COAs headline a single purity figure. Read what stands behind it, not just the number.

• ·Purity by HPLC (usually RP-HPLC at 214/220 nm) — reported as area percent. Research peptides are commonly released at ≥98%; pharmaceutical-grade sits higher.
• ·Find the chromatogram itself — one dominant peak at the stated retention time is what you want to see. The method, column, gradient and mobile phase should be described alongside it.
• ·Related-substance / impurity table — individual and total impurity limits, including deletion, truncation and oxidation products.
• ·Peptide content or net peptide assay — this is distinct from chromatographic purity and tells you how much actual peptide you have by weight.
• ·Counter-ion content (acetate or TFA) — TFA residue is worth checking.

Residuals from manufacturing end up in the powder alongside the peptide. Scan the physical-testing block for these.

• ·Water content by Karl Fischer or loss on drying.
• ·Residual solvents (acetonitrile, methanol, DMF) against ICH limits.
• ·Heavy metals / elemental impurities (lead, arsenic, cadmium, mercury).
• ·pH of the reconstituted or supplied solution.
• ·Total mass or fill weight verification.

These are the assays that matter most for anything intended to be injected, and the ones most often missing from a research-grade sheet. If you cannot find them, the document is incomplete for injectable use.

• ·Bacterial endotoxin (LAL) — reported in EU/mg with a defined limit, not just a raw figure.
• ·Sterility for products presented as sterile.
• ·Microbial / bioburden limits: total aerobic count, total yeast and mould.
• ·Absence of specified organisms where applicable.
• ·Particulate matter and container closure integrity for filled vials.

Every line on a credible COA has three columns: the test, the specification (the acceptance limit), and the result, plus the method or pharmacopeial reference used (USP/EP monograph, ICH guideline, or an internal SOP number). As you read, ask of every row: what was the limit, what was measured, and by what method? A sheet listing results with no specifications, or specifications with no methods, is incomplete.

• ·Result within specification, with the specification stated — acceptable.
• ·Result with no stated limit — you cannot judge it; treat as incomplete.
• ·A test row that simply reads “pass” with no number — a red flag worth a question to the supplier.