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COA & testing

A certificate of analysis is a record of specific tests run on a specific lot — not a quality rating and not a guarantee about the vial in your hand. This is everything Therapept publishes on reading that documentation and commissioning your own.

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Testing & documentation

How to Read a Peptide Certificate of Analysis

A certificate of analysis is a record of specific tests run on a specific lot. Here is what each field means, which fields are load-bearing, and the four ways a COA can be technically accurate and still tell you very little.

3 Sept 2026 · 9 min

Testing & documentation

HPLC vs LC-MS: What Each Test Actually Tells You

HPLC and LC-MS are not competing methods or tiers of the same measurement. They answer different questions — how much of one thing, and which thing — and a purity figure without an identity confirmation is a known blind spot.

3 Sept 2026 · 8 min

Testing & documentation

How Peptide Batch and Lot Traceability Works

A lot number is only useful if it resolves to something. This covers what a lot actually is, what a working traceability chain looks like end to end, and the difference between a lookup tool and lookup theatre.

3 Sept 2026 · 7 min

Testing & documentation

A Guide to Third-Party Peptide Testing

Independent testing is the only way to check a supplier's documentation rather than trust it. What to order, how to choose a laboratory, what it costs you in sample and time, and the limits of a single result.

3 Sept 2026 · 8 min

The distinction most documentation blurs

Purity, identity and net peptide content are three different results

A reversed-phase HPLC purity figure is the main peak’s share of total detected peak area. It says how much of what the detector saw is one component — not what that component is, and not what fraction of the vial’s mass it represents.

Identity needs mass spectrometry. Net peptide content needs amino acid analysis. A lot can be 99% pure by HPLC area and still be well under 99% peptide by mass, because counterion and water do not appear in that figure at all.

What each method actually shows

Terminology

Certificate of analysis (COA): A document recording the results of specific analytical tests performed on a sample from a specific lot, on a stated date, by a stated laboratory.
Chromatographic purity: The main peak's share of total detected peak area in a chromatographic run, usually reported as a percentage.
Net peptide content: The proportion of a preparation's mass that is peptide, as distinct from counterion, water and residual salts.
Mass confirmation: Comparison of an observed molecular mass against the mass calculated from a compound's intended structure or sequence.
Lot (batch): A quantity of material produced under conditions treated as uniform, identified so that test results on a sample can be attributed to the whole quantity.
Third-party testing: Analysis performed by a laboratory with no commercial interest in the result, commissioned by and reported to a party independent of the seller.

Commissioning your own analysis

12 laboratories with publicly stated peptide capability, recorded against what each one actually publishes about methods, accreditation, turnaround and sample requirements.

Testing laboratory directory

Working checklists

A field-by-field COA audit sheet and a supplier documentation review checklist, published in full with no sign-up.

Open the checklists