How to check a supplier's certificate of analysis before you buy
A certificate of analysis can be genuine and still describe the wrong batch, the wrong specification or the wrong site. Here is how to read one at a desk before any money moves.
How do you check a supplier's certificate of analysis before you buy?
Check that the certificate names the manufacturer and its site, that the batch number, dates and quantity match the goods offered, and that every test and acceptance criterion matches your agreed specification and pharmacopoeial edition. Then confirm a named quality unit released it, compare it with earlier batches, and ask the manufacturer to confirm it directly.
A certificate of analysis is usually the first quality document a buyer sees, and often the only one attached to a quotation. It arrives as a single page with a table of tests and the word complies down the right hand column. That page is easy to accept and easy to misread. A certificate can be genuine and still describe a different batch, a different specification or a different site from the one you think you are buying from. It can also be copied, edited or assembled by someone who never handled the material.
Checking a certificate does not need a laboratory. It needs the specification you agreed, a little patience, and a habit of reading every line as a claim that someone should be able to support. The checks below can be done at a desk before any money moves.
How do you check a certificate of analysis before you buy?
Read it in three passes. The first asks who issued it and for what. The second asks whether each result fits the specification you agreed. The third asks whether the document hangs together as a record of real work. Most problems show up in the first pass, which is why it comes first.
Who issued it, and for which site?
The certificate should name the manufacturer and the manufacturing site, not only a trading name or a sales office. Compare that name and address with the site named on the GMP certificate, the drug master file or the registration you are relying on. A certificate on the letterhead of a distributor, with no manufacturer named, tells you who sold the material, not who made it. It should also show who released the batch: a named person in the quality unit, a signature or an approved electronic equivalent, and a date of issue.
Does the batch match the goods on offer?
Check the product name, grade and batch number against the proforma invoice and, later, the drum labels. Check the manufacturing date and the retest or expiry date, and make sure they make sense against each other and against the date of the offer. Check the batch size against the quantity being sold. A batch that appears to supply more material than it could have contained, or a certificate dated before the material was made, needs an explanation before anything else.
Does each result match the specification you agreed?
Lay the certificate beside your own specification, line by line. Every test you require should appear, with the same acceptance criterion and a reported result. Missing tests matter more than failing ones, because a missing test is easy to overlook. If your specification follows a pharmacopoeial monograph, the certificate should say which pharmacopoeia and which edition. Monographs are revised, and a certificate written against an older edition may omit a test that the current one requires.
Acceptance criteria and test requirements belong to the monograph, the guideline and the registration that apply in your market. Confirm them there rather than taking the certificate's version on trust.
Look at the results, not only the word complies
A result should be a value where the test produces a value: an assay figure, a water content, a named impurity with its level. A column that reads complies for every quantitative test hides the information you need to judge how close the batch sits to its limits. Results reported to more precision than the method can deliver, or every impurity reported at exactly the same level, are worth a question. So is an assay that sits at the same value across every batch you have seen.
What signs suggest a certificate has been altered or copied?
Compare the certificate with others from the same supplier. Genuine certificates from one site share a layout, a numbering system and a set of signatories, and their results vary a little from batch to batch, as real measurements do. Identical results on certificates for different batches suggest a template rather than a test. Fonts that change within a table, a batch number that looks pasted in, a stamp that sits over text it should sit under, or a scanned signature that is pixel for pixel the same on every document are all reasons to slow down.
None of these signs proves fraud on its own. Each one is a reason to ask the manufacturer to confirm the certificate directly, using contact details you obtained independently rather than those printed on the document.
A certificate is a claim, not a proof. It is only as reliable as the link between the page, the batch and the site that tested it. Before you buy, confirm that the manufacturer named on the certificate made the batch, that the tests match your specification, and that the manufacturer will confirm the document if asked.
What should you ask for alongside the certificate?
Ask for the specification the certificate was issued against, so that you can compare like with like. Ask for certificates from two or three previous batches, which lets you see how results move over time. Ask whether the certificate is the manufacturer's original or a reissue, and if it is a reissue, ask for the original as well. For a first order, consider having a retained sample or a sample from the shipment tested by an independent laboratory against your own specification. Where a drug master file or a certificate of suitability exists, the specification in that file should match the one on the certificate.
What changes when the certificate comes through a trader?
Many buyers receive certificates through a trading company or distributor, and that is normal. What matters is that the manufacturer's original certificate reaches you unchanged. A trader may add its own covering certificate, but it should not replace the manufacturer's document, retype its results or remove the manufacturer's name. If a supplier will not disclose the manufacturer, you cannot check the certificate against anything, and that is itself the answer to the question.
Reading the impurity section properly is covered in our guide to reading an API impurity profile, and the site details on the certificate should be checked against what a GMP certificate actually proves. When the goods arrive, the same certificate is checked again at incoming goods inspection. Certificates of analysis are among the documents we check as part of our independent verification work.
NJMC Medical Supplies Co., Ltd is a trading and consultancy company in Nanjing, China, supplying medical equipment, medical consumables and active pharmaceutical ingredients to healthcare institutions, sourced from manufacturers in China and India.
Frequently asked questions
Can a genuine certificate of analysis still be the wrong one?
Yes. A certificate can be authentic and still describe a different batch, a different grade or a different manufacturing site from the material you are being offered. Match the batch number, product name, grade and site against the invoice, the labels and the GMP certificate before relying on any result printed on it.
Is a certificate that says complies for every test enough?
Usually not. Where a test produces a number, such as assay, water content or a named impurity, the certificate should report the number. A column of complies hides how close the batch sits to its acceptance criteria and makes it impossible to compare one batch with the next. Ask for the actual results.
How do I confirm a certificate with the manufacturer?
Find the manufacturer's contact details independently, from its own website, its registration or a previous verified contact, not from the certificate itself. Send the batch number, the certificate number and a copy of the document, and ask the quality unit to confirm that it issued it and that the results match its records.
Should I test the material myself if the certificate looks right?
For a first order or a new supplier, independent testing against your own specification is a sensible check. It confirms that the material matches the certificate, not only that the certificate matches the specification. Over time, periodic testing of selected batches shows whether the supplier's certificates remain reliable.
Check a certificate of analysis. PharmaTrust by NJMC, our own software, reads a certificate against the applicable specification and lists the points to raise with the supplier. Certificate check
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