A laboratory issues a Certificate of Analysis to report what it found when it tested a batch. It answers one question: is the sample what its label says? The sections below cover the results a COA should contain, how to read each one, and what makes the certificate itself trustworthy.
01 / PURPOSEWhat a Certificate of Analysis establishes
A COA reports the results of specific tests run on a specific batch. A complete certificate answers three questions about that batch: whether the sample is pure, whether it is the compound stated, and whether the amount present matches the amount on the label.
02 / THE THREE PRIMARY RESULTSWhat each result confirms, and what its absence hides
Three results describe the sample. Knowing what each one shows — and what stays unknown when one is missing — is most of reading a COA.
The fraction of the sample that is the target peptide rather than impurities, reported as a percentage (commonly 98–99% or higher). Most certificates report this value first.
Expected: a percentage accompanied by the supporting chromatogram, not a value on its own. Deficiency: a purity figure with no supporting data.
Confirmation that the sample is the compound stated, not a structurally similar or mislabeled one. A sample can be pure and still be the wrong compound; purity does not address identity.
Expected: an explicit identity result, usually marked "MS" or "LC-MS." Deficiency: no identity result, meaning the compound was never confirmed.
The measured amount of peptide in the vial (in mg) against the labeled amount. This result is the one most often omitted, and frequently the most important. A sample can be pure and correctly identified yet contain more or less than stated, and purity says nothing about quantity.
Expected: a measured content or assay value in mg, stated against the label. Deficiency: no content result, leaving the most common problem — a wrong amount — unmeasured.
A certificate reporting purity alone answers one of the three questions. A complete certificate answers all three.
03 / A COA, LINE BY LINEThe function of each element
Below is a simplified certificate with each element labeled. These are the parts to examine on a real one.
| Element | Value | What it tells you |
|---|---|---|
| Sample / Lot code | LOT-2026-0031 | Identifies the batch |
| Date of analysis | 2026-01-14 | Results are time-bound |
| Purity (HPLC) | 99.1% | Result 1: purity |
| Identity (MS) | Confirmed | Result 2: identity |
| Content / assay | 4.9 mg / 5 mg | Result 3: content |
| Issued by | Example Labs (independent) | Accountable party |
| Verify at | verify.example/EX-0000 | Basis for verification |
The parts to examine. The three test results — purity, identity, content — describe the sample; the lot code, date, issuing laboratory, and verification reference determine whether the document can be trusted. The fewer of these a certificate includes, the less it proves. Illustrative example only.
04 / RELIABILITYWhat distinguishes a reliable certificate
This matters most of all. Edited, reused, and fabricated certificates are common — a number changed, a date swapped, or another lab's report reissued under a new name. A certificate's numbers mean nothing if the document itself cannot be trusted.
Four things separate a reliable certificate from one that only looks reliable:
The issuing laboratory. An independent lab — one with no stake in the sample — has no reason to flatter a result. A certificate written by whoever supplied the sample is not independent verification.
Verifiability. A reliable certificate can be checked against the lab's own permanent record, through a code or link that returns the original result. A certificate that exists only as an image or PDF can be altered with no trace.
Batch attribution. A lot code and date tie the certificate to one batch. Without a lot code, it cannot be matched to anything.
Supporting data. A lab that stands behind its work shows the data — the chromatogram, for example — names its methods, and signs the result.
05 / THE DECIDING CRITERIONVerifiability
The other three criteria all depend on this one. A number that cannot be traced back to the lab that produced it is a number taken on faith. A certificate held at a permanent record — issued by the testing lab and checkable by anyone — is the only kind whose results can be confirmed rather than assumed.
A certificate that cannot be verified proves nothing.
Summary criteria
- Reports purity, identity, and content — not purity alone
- Identity confirmed by an MS / LC-MS result, not omitted
- Content measured (mg per vial) against the labeled amount
- Includes a lot code and date of analysis
- Provides the supporting data or chromatogram, not a value in isolation
- Issued by an independent laboratory
- Verifiable against the laboratory's own record
The more of these a certificate fails, the less it tells you.
Certinum Labs
Certinum Labs is an independent analytical testing laboratory for research peptides. We test purity, identity, and content, and issue verifiable certificates. We sell no product and hold no stake in any vendor — we only measure.
Research use only. Not for human consumption. This note is educational and concerns the interpretation of a certificate of analysis; it does not constitute guidance on the use of any compound.