How to read a peptide COA

A Certificate of Analysis (COA) is the analytical report for one specific batch of material. It records what was tested, how it was tested, which laboratory performed the work, and the results obtained. A COA describes that batch only — it is not a general statement about a product name.

When reading a report, always match the batch or lot identifier and test date on the document to the batch in front of you. If those do not match, the report does not apply.

Reverse-phase high-performance liquid chromatography (RP-HPLC) separates the components of a sample as they pass through a column. Each component appears as a peak on a chromatogram, and the purity figure is the area of the main peak expressed as a percentage of the total peak area.

Read the number together with the chromatogram: a clean baseline and a single dominant, symmetrical peak support the stated figure. A purity percentage quoted without a chromatogram, a method description, or a laboratory name cannot be verified.

Purity is method-dependent. The same sample analysed with a different gradient, column, or detection wavelength can produce a slightly different figure, which is why the method must appear on the report.

HPLC shows how much of the main component is present; it does not prove what that component is. Mass spectrometry (often LC-MS) measures molecular mass and confirms identity by comparing the observed mass with the theoretical mass calculated from the sequence.

A complete report shows both: an observed mass consistent with the expected value, and a purity result from chromatography. A report with only one of the two answers only half the question.

Labeled quantity is what the vial states; net content is what the laboratory measured. Comparing them shows whether the vial contains at least the labeled amount, and it matters for any dilution calculation.

Endotoxin and microbial sterility are separate tests with their own results — typically reported as a pass/fail limit and as growth or no growth. They say nothing about chemical purity, and purity says nothing about them.

Independent analytical testing means the laboratory that produced the report is a separate organization from the supplier. The report should name that laboratory, its methods, the test date, and — when documented — the analyst or director responsible.

Naming a laboratory does not imply that it manufactures, distributes, endorses, or approves any product. Laboratory attribution should be read as exactly what the document states, and nothing more.

Batch or lot identifier present · test date present · analytical method named (for example RP-HPLC, LC-MS) · laboratory named · purity result with a chromatogram · identity confirmed by mass · labeled quantity and measured net content · endotoxin and sterility results where applicable.

If any of these is missing, treat the figure as unverified rather than assuming it. No analytical result should be displayed or relied upon until a corresponding report has been verified.