What Is a Certificate of Analysis (COA) for a Research Peptide?
A Certificate of Analysis (COA) is a batch-specific document that records the laboratory test results for one production run of a compound. It states the compound name, the lot or batch number, the analytical methods used, the measured results, and the dates those results were produced. A COA documents the material that was tested — nothing more. This page explains what a COA is, why it exists, which fields a complete certificate carries, and what each line records, as plain documentation reference.
Research use only. Not for human or animal consumption. This page is technical reference material about laboratory documentation. It does not describe any use, effect, or outcome of any compound.
What a COA is, in one paragraph
A COA is an analytical record, not a marketing sheet. It links a named compound to a defined set of measurements — for example an HPLC purity figure and an LC-MS identity result — produced on a stated date and tied to a single lot or batch number. The defining feature of a real COA is traceability: the lot number on the certificate matches the lot number printed on the vial, and every result names the method that produced it. A document listing a compound name and one percentage, with no method, no lot, and no date, is not a usable COA.
Why a COA exists
A COA exists so a specific batch can be described in measurable, repeatable terms. Each production run is its own batch, so each batch gets its own certificate. That is what makes lot-to-label matching possible: you take the lot number off the vial, find the same lot number on the COA, and confirm they match character-for-character. Without a per-batch record there is nothing to match a vial against. The certificate also fixes the testing in time, through a test date and a report date, so the results can be tied to the run they belong to.
The fields a COA records
A complete certificate is built from a short list of fields. Each line records one fact about the batch:
- Compound name — the exact name of the material as tested, used to cross-check the vial label and the order.
- CAS number — the unique chemical identifier, where one exists, independent of brand naming.
- Lot / batch number — the identifier tying the results to one production run; the field used for lot-to-label matching.
- Molecular formula and molecular weight — the reference values a mass-based method is checked against.
- Appearance — a short factual description of the physical form, such as a lyophilised powder.
- Test method(s) — the named technique behind each result, typically HPLC and MS / LC-MS.
- Purity result — the measured value attributed to its method (almost always HPLC).
- Identity result — the measured mass against the expected molecular weight, from mass spectrometry.
- Test date and report date — when the analysis was run and when the certificate was issued.
- Specification vs result — the threshold the batch was checked against, shown next to the value actually measured.
- Testing party / signatory — who performed or authorised the testing.
For a line-by-line walkthrough of these fields, see how to read a peptide coa.
The two core test methods
Most peptide COAs report two complementary measurements. HPLC (High-Performance Liquid Chromatography) separates a sample into its components and reports purity — the proportion of the sample that is the target peak. MS / LC-MS (Mass Spectrometry) measures the molecular mass of the component and compares it to the expected molecular weight, confirming identity. HPLC records how much; MS records what it is. A certificate that reports only one of the two leaves a question open. The difference between the two methods is covered in detail in hplc purity vs ms identity.
What each line on a COA records (quick reference)
| Line on the COA | What it records |
|---|---|
| Compound name | The material as tested |
| CAS number | Unique chemical identifier, where one exists |
| Lot / batch number | The run the results belong to |
| Molecular formula / weight | The reference values checked against |
| HPLC purity | Proportion of the sample that is the target peak |
| MS / LC-MS identity | Measured mass vs expected molecular weight |
| Test / report date | When the analysis was run and issued |
| Specification vs result | The threshold and the measured value |
| Testing party | Who performed or authorised the testing |
A supplier-issued COA and an independent lab report record overlapping fields from different sources; the distinction is set out in supplier coa vs third party.
Where to go next
- Read a certificate field by field: how to read a peptide coa
- Understand the two core methods: hplc purity vs ms identity
- Compare a supplier COA with an independent report: supplier coa vs third party
Research use only. Not for human or animal consumption. This page is reference documentation about laboratory certificates and does not describe any use, effect, benefit, dose, or outcome of any compound.
FAQ
What is a Certificate of Analysis (COA)?
A Certificate of Analysis is a batch-specific document that records the laboratory test results for one production run of a compound. It states the compound name, the lot or batch number, the test methods used (such as HPLC and MS / LC-MS), the measured results, and the test and report dates. It documents the material that was tested, and ties those results to a single lot number.
Why does each peptide batch need its own COA?
Each production run is its own batch, so each batch is tested and documented separately. A per-batch certificate is what makes lot-to-label matching possible: the lot number on the vial is checked character-for-character against the lot number on the COA. A single certificate reused across every batch is not batch-specific and cannot be matched to a particular vial.
What fields should a complete COA contain?
A complete COA should record the compound name, the CAS number where one exists, the lot or batch number, the molecular formula and weight, the appearance, the named test methods, the purity result, the identity (mass) result, the test and report dates, the specification alongside the result, and the testing party or signatory.
What is the difference between purity and identity on a COA?
Purity is a quantity figure, usually measured by HPLC, recording how much of the sample is the target peak. Identity is a mass figure, usually from MS or LC-MS, recording whether the measured mass matches the expected molecular weight of the named compound. HPLC records how much; MS records what it is. A complete COA reports both.
Is a COA the same as a product description?
No. A COA is an analytical record of measurements made on a specific batch, with each result attached to a named method and a date. A product description is marketing copy. A document that lists a compound name and a single percentage with no method, no lot number and no date is not a usable COA.
Research use only. Not for human or animal consumption.