Start with the material, not the pass statement
A certificate of analysis is useful only when it identifies the material you are considering. Compare product name, botanical or chemical identity, plant part where relevant, grade and full composition with the proposed specification. A report for a capsule, blend or different extract is not automatically evidence for the raw material in your request. Ask the source to explain any naming difference before treating the document as applicable.
Match the batch, dates and document version
Record the batch identifier and check manufacturing, issue and retest or expiry information where provided. Confirm which lot is offered and whether the document is a reference example or applies to the proposed supply. If two copies for one batch contain different values, request the controlled version and an explanation. Do not silently choose the more favorable value. Keep the accepted specification and applicable document version together in the purchasing record.
Read limits and actual results as separate fields
A limit describes the acceptance requirement; a result describes what was reported for the tested sample. Compare the parameter name, unit and basis before judging the number. If a numerical result is outside its stated limit but a conclusion says “conforms”, ask the supplier to resolve the discrepancy with supporting records. A general pass statement does not explain the inconsistency. Your technical team should review the resolved document before accepting that specification.
Confirm what the method measures
An assay should identify the analyte, analytical procedure and reporting basis. UV and HPLC percentages are not automatically interchangeable. A marker result, a broader compound-group result and a chromatogram peak-area percentage should not be treated as the same claim without the applicable method and calculation. Ask for reference-standard information and method applicability to the exact material. A procedure written for one plant part or grade is not automatically a method for another.
Check which quality questions the COA answers
List the identity, assay, physical, contaminant, microbiological and other parameters needed for your purchase. Compare that list with what the proposed specification and COA actually cover. Ask about the test method, reporting units, sample identity and applicable limits. A result for total heavy metals does not itself answer every question about individual elements. Additional testing, documents, costs and supplier scope are confirmed for the proposed order; they are not assumed to be included.
Keep different documents in their proper roles
Use a grade specification to review proposed requirements and a matching COA to review reported batch results. An assay procedure explains the measurement approach. An SDS provides handling and safety information; it does not replace a purity result. A supplier certificate concerns the named holder and stated scope, rather than proving every batch result. If a third-party report is offered, check the laboratory, sample identification, date, test scope and relationship to the proposed lot.
Connect the sample to an acceptance decision
Before evaluating a sample, agree its identity, quantity, batch and supporting records. Define which tests or formulation observations your team will perform and how acceptance will be recorded. Ask how the sample relates to the later offered lot. A successful trial in one formula does not establish performance in every application. Document accepted limits and methods, packaging and storage requirements, any further verification and the responsibilities agreed for the order.
Send a focused document request
Include the ingredient, target grade, assay method, quantity, application and destination. Request the proposed specification, current-lot COA and relevant analytical or source information. Identify any unresolved issue in plain language: which field differs, which method is unclear or which required parameter is missing. We coordinate these questions with the proposed source and bring the responses together. File availability, sample arrangements and commercial terms are confirmed for the actual request; the purchasing decision remains tied to the reviewed material and agreed requirements.
A practical COA reading checklist
| Check | What to compare | Question to ask |
|---|---|---|
| Identity & batch | Product, grade and sample/batch identification | Does the record match the material being offered? |
| Specification limit | Parameter name, units and accepted limit | Is the limit the one in the proposed purchase specification? |
| Method | Procedure and reporting basis | Does the method apply to this analyte and grade? |
| Reported result | Actual result against the stated limit | Is the result reported clearly and within the agreed limit? |
| Dates & scope | Manufacture, issue, retest or expiry information | Are the dates and document scope applicable to the offered lot? |
Read the method, limit and actual result together
FDA guidance on dietary-supplement manufacturing discusses supplier COAs that include test methods, limits and actual results, alongside conditions for relying on a supplier COA. Use that context to define document questions for your proposed material.
FDA: dietary-supplement manufacturing guidance ↗Read for the stated purchasing context. This source does not certify our company or establish approval of an offered material. Reference checked 27 October 2026.