How to read a Certificate of Analysis (COA)

Every Merit lot ships with a Certificate of Analysis (COA) — a document from the third-party laboratory that performed the release tests on that specific batch. This walks through every section of a typical research-peptide COA, what each measurement means, and what to look for vs. what to disregard.

The COA at a glance

A complete research-peptide COA contains six functional blocks:

1. Identification — peptide name, sequence, theoretical mass, lot number, manufacturing date
2. Appearance — physical description of the lyophilized product
3. Identity confirmation — mass spectrometry result confirming the molecule
4. Purity — HPLC chromatogram with AUC percentage
5. Microbial / endotoxin — bioburden screen for parenteral-grade compliance
6. Method block — instrumentation, columns, gradients used for the tests

What to verify when the COA arrives

1. Lot number matches the vial

Check the lot number printed on the vial against the lot number on the COA. They must match. If they don't, the COA you received is not for the lot in your hand — contact Merit immediately with both numbers.

2. Identity confirmation passes

The mass spectrometry section shows the observed mass compared to the theoretical mass calculated from the peptide sequence. A pass means the observed value is within tolerance (typically ±0.5 Da for small peptides, slightly looser for large ones). If the COA marks this PASS, the molecule in the vial is the molecule on the label.

3. Purity ≥ Merit's release floor

Merit's release floor is 99% AUC. Look for the headline number on the HPLC section. Any lot below 99% is rejected and does not ship — so any COA you receive should show ≥99%. If it doesn't, contact Merit.

4. Endotoxin ≤ 1 EU/mg

For peptides intended for parenteral research use (most peptides in this catalog), the COA should report bacterial endotoxin testing (BET / LAL assay) with a result of <1 EU/mg. This corresponds to USP <1> parenteral-grade compliance. Higher values mean the peptide carries residual lipopolysaccharide that can confound research models even after sterilization.

5. Method block makes sense

The method section records the analytical setup. You don't need to be an HPLC expert to verify two things:

• Detection wavelength is 220 nm — the standard for peptides. (215 nm is also occasionally seen.)
• Column is C18 — the standard reversed-phase column for peptides.

Non-standard methods aren't necessarily wrong, but they're worth a second look — they may have been chosen to make impurity peaks elute outside the integration window.

What to disregard

Two things on most COAs are essentially decorative:

• Theoretical molecular formula. Useful for chemists, irrelevant for benchwork.
• Manufacturing technique description (SPPS, etc.). Standard for all synthetic peptides; doesn't tell you anything about this specific lot.

Reading the HPLC chromatogram

The chromatogram is the most information-dense part of the COA. Things worth looking at:

• One dominant peak at the expected retention time — that's your target.
• Small impurity peaks on either side — normal. Their total area is captured in the "other peaks" percentage.
• A flat baseline between peaks — indicates good methodology and no instrument drift.
• Integration markers visible on the trace — confirms which peaks were counted.

If the chromatogram shows the main peak and a second peak nearly as tall, something is wrong — that lot has a major impurity or contamination. Don't use it.

Where Merit keeps your COA

After purchase, the COA for the specific lot you received is permanently linked to your order in your account dashboard. You can re-download it any time. Pre-purchase, the COA for the current shipping lot is linked from each product page.

For research use only. The COA is the authoritative document for your lot's release tests; this article is interpretive guidance only.