Laboratory guides
How to read a certificate of analysis
How to check a batch COA and assess a supplier: identity, purity, content, issuing laboratory and the limits of each result.
Match the vial batch to the document, identify the issuing laboratory, and separate specification, method and result. Identity, purity and content answer different questions. An HPLC area percentage alone establishes neither vial milligrams nor sterility.
Checks before accepting the document
A COA reports on the analyzed sample. Relating that sample to a batch requires identification and, where relevant, sampling information. A commercial name alone does not connect the report with the received vial.
| Field | What to check |
|---|---|
| Sample and batch | Match the vial. Where manufacturer and distributor identifiers differ, request their documented correspondence. |
| Issuer and document | Identifiable laboratory, report number and complete pages. |
| Tests | Method, acceptance criterion and result for each test, with units or calculation basis. |
| Traceability | Sample receipt, report approval and relevant information establishing when analysis occurred. |
| Scope | The sample evaluated, tests performed and determinations not included. |
Specification, result and conclusion
The specification states the requirement; the result records the observation under the method; the conclusion states whether it meets that requirement. These are distinct fields even when presented in one table.
A conforms statement may be appropriate for a qualitative test. To interpret a quantitative result, ask for its value and how it was obtained. Similar results across batches do not prove fraud, but neither do they prove that every batch was tested.
Identity, purity and content need different evidence
An identification method needs enough selectivity to distinguish relevant alternatives. A compatible mass is useful evidence but does not exclude every equal-mass structure. Selectivity and potential interferences limit the conclusion.
In an area-based purity result, integrated signals form the denominator. Determining content per vial requires an appropriate quantitative method and a stated calculation basis. The related guides explain that distinction.
Assessing research peptide suppliers in Mexico
Pureza suggests applying the same checklist to our catalog and other suppliers: request documentation for the material to be received rather than relying on a promotional image.
- Request the available batch COA and storage conditions before deciding whether the material suits the protocol.
- Clarify whether declared milligrams refer to gross mass, peptide content or the target compound amount.
- Verify the issuer through a contact channel obtained independently from its official site. A QR code leading back to the seller is not independent verification.
- If ISO/IEC 17025 accreditation is claimed, check the accrediting body, current status and scope for the particular activity. A logo does not cover every laboratory test.
- Compare seller identification, invoicing, delivery traceability and a clear procedure for resolving batch discrepancies.
When information is missing
Record the discrepancy and request the complete report or clarification from the issuer. A missing field does not automatically establish a counterfeit product, but it limits the conclusion. Do not accept material for a protocol when the available evidence does not cover its requirements.
Scope of the references
The WHO model is a pharmaceutical laboratory documentation reference used here to explain traceability, results and specifications; it does not establish certification of Pureza. ILAC explains activity-specific accreditation. ICH Q2(R2), particularly sections 3.1 and 3.1.2, provides an analytical framework for selectivity, interference and identification, not approval of these research materials.
Questions and answers
Does high purity on a COA establish sterility?
No. Identity, purity and sterility are separate attributes. A report supports only its stated determinations; an HPLC percentage is not a microbiological test.
Can another batch’s certificate support the vial I received?
It can illustrate a supplier’s format, but not establish results for your batch. Request the corresponding document or the documented relationship between manufacturer and distributor identifiers.
Does laboratory accreditation cover any analysis?
No. Accreditation concerns specified activities. Check that the reported test falls within the current scope published by the accrediting body.