How to read a peptide COA

A Certificate of Analysis (COA) is the single most important document in peptide research. It is the analytical proof that the compound in your vial is what the label says it is, at the purity the supplier claims. Without it, you are trusting a label. With it, you are trusting data.

Yet most researchers have never been taught how to read one. The chromatograms, molecular weights, and percentage figures can look intimidating if you have not worked in an analytical chemistry lab. This guide breaks down each section of a peptide COAso you can evaluate any supplier’s documentation with confidence.

The bottom line: if your supplier cannot provide a batch-matched COA for the specific product you are purchasing, that is not a supplier — that is a gamble. Every order from Titan Peptide Lab ships with a COA matched to your exact batch. Here is how to read it.

High-Performance Liquid Chromatography (HPLC) is the gold standard for peptide purity assessment. It separates the components of a sample by running it through a column under high pressure, with each component emerging at a different time based on its chemical properties. A detector (usually UV at 220nm for peptides) measures how much of each component is present.

Reading the chromatogram

The HPLC chromatogram is the chart you will see on most COAs. The x-axis shows retention time (minutes), and the y-axis shows detector response (absorbance). Your target peptide appears as a single dominant peak. Here is what to look for:

• Main peak area percentage — This is the purity number. It tells you what fraction of the total sample is your target peptide. For research-grade peptides, you want 99% or higher. Anything below 95% should raise questions.
• Peak shape — A clean, symmetrical peak indicates a well-resolved, pure compound. Shoulders, tailing, or broadening suggest co-eluting impurities that may not be fully captured in the area percentage.
• Baseline noise — Small peaks scattered across the baseline represent trace impurities (truncated sequences, deletion products, or degradation fragments from synthesis). In a 99%+ purity sample, these should be minimal.
• Retention time — The main peak should appear at the expected retention time for the target peptide under the stated column and mobile phase conditions. This is a rough identity check — mass spec provides the definitive one.

What HPLC does not tell you

HPLC measures purity — the percentage of the sample that is your target compound. It does not confirm identity. A 99% pure peak could theoretically be the wrong peptide at 99% purity. That is why mass spectrometry is the essential complement to HPLC on any serious peptide COA.

Mass spectrometry (MS) confirms that the molecule in your vial has the correct molecular weight — and therefore the correct amino acid composition. This is the identity test that pairs with HPLC’s purity test.

How to read MS data on a COA

The MS section of a peptide COA typically shows a spectrum with peaks at specific mass-to-charge (m/z) ratios. The key number to verify is the molecular weight of the target peptide. For common research peptides:

• BPC-157 — 1419.53 Da (free acid) or 1419.53 + counter ion for salt forms
• Semax — 813.93 Da
• Selank — 751.88 Da
• PT-141 — 1025.18 Da
• Oxytocin — 1007.19 Da
• DSIP — 848.82 Da

The observed molecular weight on the MS spectrum should match the theoretical value within the instrument’s tolerance (typically ±0.1 Da for ESI-MS). If the observed weight is off by more than 1 Da, the sample may contain the wrong peptide, a deletion sequence, or a modification not reflected in the product label.

Some premium COAs include amino acid analysis — a test that breaks the peptide down into individual amino acids and quantifies each one. This confirms not just the molecular weight (which MS already does) but the actual composition of the chain.

For most research applications, HPLC + MS is sufficient. AAA is valuable when working with longer peptides where isobaric substitutions (amino acids with the same mass but different identity) could produce the correct molecular weight from the wrong sequence. For the peptide nasal sprays most commonly used in research (BPC-157, Semax, Selank, PT-141, Oxytocin, DSIP), HPLC + MS is the practical standard.

For injectable peptides, endotoxin testing (LAL assay) is critical — endotoxins are bacterial cell wall fragments that cause fever and inflammation in biological systems. The COA should report endotoxin levels below 5 EU/mg for research-grade injectables.

For peptide nasal sprays, endotoxin testing is less universally required but still a quality marker. The intranasal route does not introduce compounds directly into the bloodstream, but endotoxin contamination indicates poor manufacturing hygiene. A supplier who tests for endotoxin in nasal spray products is operating at a higher standard than one who does not.

Sterility testing (confirming the absence of viable microorganisms) is another quality indicator. While not legally required for research-use-only products, it reflects the manufacturing standard. All Titan Peptide nasal sprays are produced under conditions designed to minimize microbial contamination.

After reviewing hundreds of COAs from different suppliers, here are the patterns that should make you question a peptide COA:

• No batch or lot number — A COA without a batch number cannot be traced to a specific synthesis run. It might be a template document reused across multiple batches, which defeats the purpose entirely.
• Purity stated but no chromatogram shown — Saying “99.2% purity by HPLC” without including the actual chromatogram is like claiming a lab result without showing the data. The chart is the proof.
• No mass spectrometry data — HPLC without MS tells you the sample is pure but not necessarily that it is the right compound. This is a significant gap.
• Inconsistent dates or formatting — COAs that look like they were edited in a word processor, with mismatched fonts, inconsistent date formats, or no lab letterhead, may not be genuine analytical reports.
• Purity below 95% — While 95% is acceptable for some research applications, purity below 95% means 5%+ of the sample is impurities — truncated sequences, deletion products, or degradation fragments that could confound your results.
• Same COA for multiple products — Every peptide product and every batch should have its own COA. If a supplier uses the same document for different products or batch dates, the testing is not batch-specific.

Use this checklist every time you receive a peptide COA from any supplier:

1. Batch/lot number present and matches your order
2. HPLC chromatogram included (not just a purity number)
3. Main peak area percentage is 99% or higher
4. Peak shape is clean and symmetrical
5. Mass spec data confirms correct molecular weight
6. Testing lab identified (in-house or third-party)
7. Date of analysis is recent and appropriate for the batch
8. Document formatting is professional and consistent

If a COA passes all eight checks, you can have reasonable confidence in the product. If it fails more than one, ask the supplier for clarification — or find a different supplier.

See our Lab Testing page for examples of the documentation we provide with every Titan Peptide order.