The Certificate of Analysis explained

A Certificate of Analysis (COA) is the document a third-party laboratory issues to certify that a specific production lot of a peptide passed a defined set of release tests. It's the most important piece of paper that ships with research peptides — and it's the thing you should verify before any lot enters your workflow.

What's actually on a COA

A complete research-peptide COA covers six categories of information:

1. Lot identification

• Peptide name (e.g., "Tirzepatide")
• Sequence (e.g., "YXEGTFTSDYSIYLDKQAAXEFVQWLLAGGPSSGAPPPSC-NH₂" — with X marking non-standard residues)
• Lot number (the unique batch ID)
• Manufacturing date and expiration / retest date
• Quantity per vial

2. Appearance

A short physical description: "White lyophilized powder" or "White to off-white amorphous solid." Anything unusual (yellow, crystalline, oily) is a red flag.

3. Identity confirmation (mass spectrometry)

Observed mass vs. theoretical mass calculated from the sequence. Within tolerance = identity confirmed.

4. Purity (HPLC)

Area-under-curve percentage of the main peak vs. total integrated peak area. Merit's floor is ≥99%.

5. Bioburden / endotoxin

For peptides intended for parenteral research use, the COA reports:

• Bacterial endotoxin (LAL assay) — in EU/mg, typically <1 EU/mg
• Total aerobic microbial count — typically reported as <10 CFU/g
• Mold and yeast — typically <10 CFU/g

6. Method block

The analytical conditions used for each test — column type, gradient, detection wavelength, instrumentation, ionization mode. This lets the test be reproduced by a second lab if a question ever arises.

Who issues the COA

Two paths exist in the industry:

1. In-house COA — the manufacturer's own QC lab tests and issues the certificate. Faster, cheaper, but the manufacturer has an obvious incentive to pass borderline lots.
2. Third-party COA — an independent contract testing laboratory tests the lot and issues the certificate. Adds cost and time, but independence is meaningful.

Merit uses third-party COAs exclusively. The third-party laboratory is named on every certificate.

Verifying the COA against the vial

Three checks anyone should do on receipt:

1. Lot number match. The number on the COA must match the number printed on the vial label. If they don't, you have either the wrong COA or the wrong vial — contact the supplier immediately.
2. Manufacturing date is recent enough. Lyophilized peptides have a 24-month shelf life. A COA dated 23 months ago is a yellow flag — the lot is approaching expiration.
3. All test sections pass. Each section should report a result and a pass/fail (or quantitative value within spec). A section marked "not tested" is missing information.

Common gaps in lesser COAs

Several patterns to watch for in supplier COAs:

• Purity reported without showing the chromatogram. "99.2%" with no trace is a number to trust at face value. The chromatogram lets you verify the integration was honest.
• Mass spec reported without showing the spectrum. Same logic.
• Missing endotoxin data. For parenteral research, endotoxin must be tested. Absence implies the peptide isn't certified for parenteral use.
• "Typical" instead of "actual" values. Some suppliers issue COAs with batch-typical numbers rather than this-lot numbers. The lot you receive may not match.

What Merit puts on every COA

For full transparency, each Merit COA includes:

• Third-party laboratory name and accreditation
• Full HPLC chromatogram (PNG embedded)
• Full mass spectrum (PNG embedded)
• Method blocks for each test
• All bioburden and endotoxin data
• Lot number traceable to manufacturing date

The COA for the current shipping lot is linked on every product page. After purchase, the COA for the specific lot you received is permanently linked to your order record.

For research use only. The COA is the authoritative document for release testing of a specific lot; this article is interpretive guidance.