Peptides MEX / Research library
How to read a peptide certificate of analysis
A certificate of analysis, or COA, should be read test by test. Before focusing on a highlighted percentage, identify the sample, method and question answered by each result. This reading sequence organizes a document review; it does not authenticate a batch or certify products in the catalog.
Updated · Sources and editorial standards
Start with the sample and lot
FDA's ICH Q7 guidance recommends identifying the material, batch and release date, alongside tests, criteria and results. Use it as a document reference: compare these fields with the sample under review and identify the issuer. A different batch number prevents direct attribution to another sample. The guidance concerns pharmaceutical ingredients; citing it does not demonstrate that a supplier complies with it.
Sources: [1]
Separate identity, quantity and purity
FDA distinguishes analytical attributes such as identity, strength, potency, purity and composition. Beside each COA test, write which question it addresses. A purity result is not, by its label, a measurement of the material's total mass. If comparing reports associated with names such as GHK-Cu and AHK-Cu, do not carry results from one to the other because the names look similar.
Sources: [2]
Find the method and its intended purpose
ICH Q2(R2) discusses validation against a method's intended purpose, including selectivity, accuracy and precision. An instrument acronym alone leaves questions unanswered. Record the procedure reference and ask what it measures, which interferences it considers and over which range it can report results. A graph without that context provides less information than a result accompanied by the procedure used to obtain it.
Sources: [3]
Read the number with its units
NIST explains that measurement estimates a property and has associated uncertainty. Record the result together with its units and any stated uncertainty instead of saving only its decimal places. Before comparing two close values, establish whether they describe the same property and how they were obtained. A number with more digits does not, by itself, establish that the result is more accurate.
Sources: [4]
Distinguish traceability from a logo
Metrological traceability connects a result to references through a documented calibration chain. NIST explains that using one of its reference materials does not automatically certify another laboratory's subsequent results. If a report claims traceability, identify the particular reference and the claim's scope. As a document-review step, cross-check the report identifier against information obtained directly from the issuer rather than relying on a logo.
Sources: [5]
Identify questions that remain untested
FDA publishes specific guidance for pyrogen and endotoxin testing. This provides a practical reminder that different attributes need appropriate tests: do not turn a chemical result into a conclusion about endotoxins. Finish with three columns: documented result, missing information and question for the laboratory. If a test is absent, record that it is undocumented rather than inventing a favorable or unfavorable result.
Sources: [6]
Questions about this reference
What should I check if the batch number is missing?
Ask the issuer to establish the connection between document and sample. Leave attribution unresolved until that information is clarified.
Does a purity figure answer every question?
No. Identify the property examined. Do not extend a test to attributes it did not evaluate.
Does a NIST reference certify the supplier?
Not automatically. Traceability needs scope and documentation; using a NIST material does not certify subsequent results.
Sources and original reading
- FDA / ICH Q7: Certificates of Analysis, section 11.4
- FDA: Part IV — Analytical
- FDA / ICH Q2(R2): Validation of Analytical Procedures
- NIST: Measurement Uncertainty
- NIST: Metrological Traceability — Frequently Asked Questions and Policy
- FDA: Pyrogen and Endotoxins Testing — Questions and Answers
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