A specification says what a grade should be. A Certificate of Analysis says what one batch was found to be.
A Certificate of Analysis (COA) looks simple: a page of rows, each with a test, a limit and a result. Much of what it tells you lies around those rows: which batch was tested, who tested it, by which method, and against which limit.
Here are seven checks to make on a COA for a botanical extract. The descriptions of a complete certificate come from the World Health Organization’s model certificate and from good manufacturing practice guidance. The examples come from our own specifications. Our earlier articles covered the specification and the extract ratio; this one covers the batch document.
01 / THE BATCH
Which batch does it describe?
A COA belongs to a batch. The World Health Organization’s model certificate describes a document that “lists tests performed on a particular sample with the results obtained and the acceptance criteria applied”, and notes that one “is usually prepared for each batch of a substance or product”.1 Good manufacturing practice guidance for pharmaceutical ingredients asks for the name of the material, its grade where appropriate, the batch number and the date of release on the certificate, and defines a batch number as a unique combination of characters “from which the production and distribution history can be determined”.2
Dates complete the identification. The WHO model includes the date of manufacture, if available, and the expiry or retest date;1 the manufacturing guidance defines a retest date as the date “when a material should be re-examined to ensure that it is still suitable for use”.2 A certificate used in trade may also state the conditions for shipping and storage on which it depends.1
The batch number on the certificate should be the number on the packaging you receive. A page of limits with no batch number and no results is a specification, whatever its title.
Check: the product name and grade, the batch number, the date of manufacture and the retest or expiry date, and that the batch is the one you are being offered.
02 / THE ISSUER
Who tested it, and who signed?
A certificate carries the name of whoever stands behind it. The WHO model lists the name and address of the laboratory issuing the certificate and “the date and signature of the head of the laboratory or other authorized person approving the certificate”.1 The manufacturing guidance says certificates should be “dated and signed by authorised personnel of the quality unit(s)”.2
Check: who issued the certificate, which laboratory performed the tests, and that it is dated and signed.
03 / THE ROWS
Does each row give the test, the limit and the result?
The body of a COA is a table. The WHO model sets out five columns: test, method reference, acceptance criteria, result and compliance statement, with results “in numerical form, whenever applicable”.1 The manufacturing guidance puts it in one sentence: the certificate should list each test performed, “including the acceptance limits, and the numerical results obtained (if test results are numerical)”.2
The United States rule for dietary supplement manufacturers shows why a buyer needs the method, the limit and the result together. A manufacturer there may rely on a supplier’s certificate only if it includes “a description of the test or examination method(s) used, limits of the test or examinations, and actual results of the tests or examinations”.3
So a row that reads “complies” is complete only when the limit stands beside it, and a numerical test should show a number. Our documented Bamboo Extract grade, for example, specifies silicon dioxide (SiO₂) at ≥75.0%, measured by ICP-OES. On a certificate for a batch of that grade, the row to look for is the silicon dioxide result, set beside that limit and that method.
Check: that every row names the test and its method, states the limit, and gives the result as a number wherever the test produces one.
04 / MEASURED OR TYPICAL
Was every row measured on this batch?
Not every figure on a certificate has to come from a test on the batch in hand. European medicines guidance on herbal preparations defines periodic or skip testing as “the performance of specified tests at release on pre-selected batches and/or at predetermined intervals, rather than on a batch-to-batch basis”, on the understanding that untested batches still meet the criteria, and it requires the practice to be justified. It also considers that contaminants usually need not be tested in the extract “if tested on the herbal substance”, the plant material the extract was made from, provided they do not accumulate during processing.4
These practices change what a row means. A result measured on this batch, a result from the last batch tested, a value carried over from the plant material and a typical value are four different statements. The WHO model asks for “the results of all tests performed on the sample for which the certificate is issued”;1 where a row is something else, ask for it to be marked.
Check: which rows were measured on this batch, which are tested periodically, and which were measured on the plant material before extraction.
05 / THE ASSAY
What exactly does the assay row measure?
The assay row carries the figure a grade is sold on, and its wording matters. A result is defined by the method, by the reference standard where one is used, and by what the result is expressed as. European guidance requires assays “with details of the analytical procedure”.4
Our cranberry extract is specified at 30% or more total soluble proanthocyanidins (PACs) by BL-DMAC / UV-Vis, expressed as procyanidin A2 equivalents. A result obtained by another method, or expressed against another standard, is not a result against that specification, even where the number is higher. Our first article quotes published figures showing how far two methods can differ on the same material.
Check: that the method, the reference standard and the expression of the result on the certificate are those of the specification you agreed.
06 / THE LIMITS
What are the contaminant rows compared with?
Heavy metals, microbial counts, pesticide residues and residual solvents appear as short rows. For herbal preparations, European guidance lists them as tests with their own references: “Residual solvents in dry or soft extracts arising from the extraction process”, “Pesticides, fumigants, mycotoxins and heavy metal/toxic element residues”, and microbial limits in line with the pharmacopoeia.4
Each of these rows is a comparison, so the question is what the result was compared with: a pharmacopoeia, a regulation or the supplier’s own limit. A limit that suits one market may not be the limit of yours. Our first article gives the current European Union and Great Britain maximum levels for metals in food supplements, and explains that they apply to the supplement as sold; what they mean for an ingredient depends on how much of it the finished product contains.
Check: the limit each result is compared with, where that limit comes from, the unit, and whether it suits your destination market.
07 / YOUR OWN CHECK
How far can you rely on the certificate?
A certificate is the supplier’s statement; your own quality system decides how much weight it carries. Under European Union food law, and in the same words in the law of Great Britain, food business operators “shall ensure that foods or feeds satisfy the requirements of food law which are relevant to their activities and shall verify that such requirements are met”.5
The United States rule shows one way of doing that. Before relying on a supplier’s certificate, a supplement manufacturer must qualify the supplier “through confirmation of the results of the supplier’s tests or examinations”, must “periodically re-confirm the supplier’s certificate of analysis”, and must still conduct “at least one appropriate test or examination to verify the identity” of each dietary ingredient, unless exempted by the agency.3 Good manufacturing practice guidance for pharmaceutical ingredients takes the same line: a supplier’s certificate can replace other tests only where the user has a system for evaluating its suppliers, and the reliability of certificates “should be checked at regular intervals”.2
A sample is the practical first step. You can request one for ingredient evaluation and have it tested; ask for the certificate of the same batch, so that the two sets of results can be compared.
Check: what your quality system requires before a supplier’s certificate is accepted, and which tests you will repeat yourself.
WHAT TO SEND
Ask for the documents with your enquiry
When you need a COA or other technical documents, tell us:
- the ingredient, and the plant part if more than one is offered;
- the grade or specification you are evaluating;
- the documents you need, such as a specification sheet or a Certificate of Analysis;
- the tests and methods your quality team requires, if they are fixed;
- your intended application and destination market;
- your estimated quantity and target delivery date;
- your name, company and contact details.
We offer technical documentation and COA support; the available document set is confirmed for each ingredient and project. You can also request a sample for ingredient evaluation. Specification ranges in our catalogue are references, and feasibility, availability and price are confirmed with your quotation.
Product examples are taken from YOHOLIFE® specifications and technical documents; confirm the selected grade and its batch COA when enquiring. Sources 1, 2 and 4 were written for medicines, and source 3 for dietary supplements made in the United States; they are cited here for what they say a certificate should contain and how far it may be relied on. Legal references were checked on 11 November 2026 and are given for orientation, not as regulatory advice.
