Home/Resources/How to Read a Peptide COA
In one minute
- A COA (Certificate of Analysis) reports what a batch actually contains, tied to a lot number.
- HPLC measures purity — how much of the sample is the target peptide.
- Astra publishes a purity COA for every batch, tied to its lot.
- Match the lot number on the COA to the vial in your hands.
- Verify by matching the lot number and reading the purity result. Start in our COA Library.
Marketing copy can say anything. A Certificate of Analysis can’t — it’s a record of measurements. Learning to read one turns “trust me” into “here’s the data,” which is exactly how research-compound quality should be evaluated.
What a COA actually is
A Certificate of Analysis is a laboratory document that records the results of testing performed on a specific batch of material. The defining feature is that it’s tied to a lot number: the COA describes that production run, not the product in general. If a document isn’t linked to a lot you can match to what’s in your hands, it isn’t doing its job.
Astra Peptides issues a COA for every batch, and publishes them in an open COA Library so you can read the document before you decide to buy.
HPLC: the purity line
HPLC stands for high-performance liquid chromatography. In simple terms, the instrument pushes the dissolved sample through a column that separates its components, and a detector records each one as a peak. The target peptide shows up as the dominant peak; impurities show up as smaller ones.
The purity percentage is the area of the target peak as a share of all peaks. A result of 99.5% means the target compound represents 99.5% of the detected material, with related impurities making up the rest. The closer to 100%, the cleaner the material. Astra Peptides holds every compound to ≥99% purity, typically 99.5%+.
What to look for
- A clearly stated purity % for the main peak.
- A single dominant peak rather than several large ones.
- The method noted as HPLC (often RP-HPLC, reverse-phase).
Identity testing (mass spectrometry)
Purity tells you how much of the sample is the target. It does not, on its own, tell you the target is the right molecule. That’s the job of mass spectrometry, which measures the molecular mass of the compound — a test some laboratories add beyond purity. The lab compares the observed mass against the theoretical (expected) mass for that peptide’s sequence. When they match, identity is confirmed.
What to look for
- An observed/found mass and a theoretical/expected mass.
- The two values agreeing within the instrument’s expected tolerance.
- A stated method such as MS, HPLC, or MALDI-TOF.
The purity: beyond a single test
A purity number and an identity confirmation are the core of any COA, but they’re a narrow view. A HPLC purity analysis widens it: it’s a battery of tests that profiles a batch across identity and purity plus additional safety and quality markers, rather than relying on a single spot-check. Astra Peptides sends every batch for independent HPLC purity analysis, and the results are summarized on the batch COA.
How to verify a COA in four steps
- Match the lot number. Confirm the lot/batch number on the COA matches the compound you’re evaluating. No match, no proof.
- Read the HPLC purity. Look for a clearly stated purity percentage from a single dominant peak.
- Check the HPLC identity. Confirm the observed mass matches the expected mass for that peptide.
- Confirm the lab is named. An independent, named laboratory — not just “third-party tested” — signals accountability.
Research use only
This guide is educational and applies to evaluating research-compound documentation. All Astra Peptides products are sold strictly for laboratory and research use only (RUO) and are not intended for human or veterinary use. Nothing here is a medical claim.Common questions
What does HPLC purity tell you on a COA?
HPLC (high-performance liquid chromatography) separates the components in a sample and reports the target peptide as a percentage of the total. A purity figure such as 99.5% means the main peak represents that share of the material, with the remainder being related impurities. Astra Peptides holds every compound to at least 99% purity, typically 99.5%+.
What is the difference between identity and purity testing?
Purity (measured by HPLC) tells you how much of the sample is the target compound. Identity (confirmed by HPLC) tells you that the compound is actually the peptide it claims to be, by matching its measured molecular mass to the expected mass. A complete COA shows both.
What does a HPLC purity analysis cover?
A HPLC purity analysis is a battery of tests that profiles a batch across identity and purity along with additional safety and quality markers, rather than relying on a single spot-check. Astra Peptides sends every batch for independent HPLC purity analysis, summarized on the batch COA.
How do I verify a COA is real?
Match the lot number on the COA to the batch you received, confirm it lists both an HPLC purity result and a HPLC identity confirmation, and check that it names the testing laboratory. Astra Peptides publishes its COAs openly in the COA Library so they can be read before purchase.
