A plain-English, field-by-field guide to a Certificate of Analysis. What each section means, what HPLC and mass spec each prove, and what a COA cannot tell you.
COA Review
A COA is a lab document. To read it, check the product name, batch number, test date, test methods used, results for identity and purity, and any limitations the lab notes. The document should clearly tie back to the specific batch you are about to receive.
From QR To COA
When a Carteum box QR code opens a COA page, the first thing to check is not the purity number. The first thing is whether the batch code on the page matches the physical label.
If the batch code does not match, stop and ask support. A COA for another batch is not evidence for the vial in front of you.
COA Fields
These are the fields to scan first. Each tells you something specific. Together they form the picture.
The document should name the exact compound, often with a CAS registry number. The name on the COA must match the product you are reviewing.
The unique identifier for the production run that was tested. Without this, the COA cannot be tied to a specific vial.
When the testing was performed and when the report was issued. An old date on a fresh batch is a mismatch.
The analytical techniques used. The two you will see most often are HPLC (for purity) and mass spectrometry (for identity). See the next sections.
Usually expressed as a percentage (e.g. 98.5%). This is the share of the sample that is the intended compound versus impurities or related substances.
Often described as white lyophilized powder or similar. Useful for cross-checking your vial against the documented batch.
The name of the testing lab, sometimes an analyst's name or stamp. A real lab will identify itself.
Some COAs include a note that the result applies only to the tested sample. Read this. It is the lab being honest about scope.
Test Methods
HPLC stands for High-Performance Liquid Chromatography. In plain English, it answers the question: how pure is this sample?
HPLC separates a sample into its parts. If a peptide is 98.5% pure, that means 98.5% of what is in the vial is the intended compound, and 1.5% is something else (related peptides, residual solvents, breakdown products).
What HPLC tells you: the share of the intended compound versus impurities.
What HPLC does not tell you: whether the main compound is actually the right peptide. HPLC measures purity, not identity. A 99% pure sample of the wrong compound still shows up as 99% pure.
Test Methods
Mass spectrometry, often written as MS or LC-MS, answers a different question: is this actually the right compound?
Mass spec measures the molecular weight of the compound. Every peptide has an expected weight. If the measured weight matches the expected weight within a small tolerance, that is evidence the compound is what the label says.
What mass spec tells you: identity confirmation. Is this BPC-157 or something else with a similar weight?
What mass spec does not tell you: how pure the sample is. Mass spec confirms presence of the right molecule. It does not, on its own, tell you what share of the sample is that molecule.
Test Methods
HPLC and mass spec each answer one half of the question. Together they give a fuller picture.
A COA that only shows HPLC, or only shows mass spec, is partial evidence. It can be honest partial evidence, but you should know what is missing.
Limits
Even a strong COA has a defined scope. It is useful to know what falls outside it.
A COA is a snapshot. A trustworthy supplier provides repeat documentation across batches over time, not just one report.