How to read a sodium chlorite certificate of analysis

Buyers sometimes ask us to publish our assay figures on the website. We do not, and the reason is worth explaining, because it goes to what a certificate of analysis is for.

A COA is a statement about a specific batch, tested by a specific method, on a specific date. A number printed on a website is a statement about nothing in particular. If the two disagree — and over a production year they will, within the tolerance the standard allows — the website number is the one that causes an argument. So we issue the certificate against the batch you are quoted, and we would rather have that conversation with a document in hand.

What to look for when you receive one. First, that the batch or lot reference on the certificate matches the batch on your packing list. This sounds obvious. It is also the single most common mismatch, usually because a sample COA was sent during negotiation and never replaced with the shipment one.

Second, the test method. A figure without the method behind it cannot be compared against another supplier's figure. This is where the production standard does real work: when two certificates cite the same standard and the same method, the numbers mean the same thing. When they do not, you are comparing two different measurements that happen to share a unit.

Third, the impurity profile, if your application is sensitive to it. For drinking water and for medical or device applications, the impurity spec often matters more than the headline assay. If your specification names particular limits, tell us at enquiry stage rather than after the first container — it is a question about which grade you need, and the grade decides both the price and the paperwork.

Fourth, that the document is about the material you actually ordered. Solid and liquid are the same compound at different concentrations and in different packing, and a certificate for one does not describe the other.

What a COA does not tell you: whether the plant that produced it runs a consistent process. That is what a management-system certificate is for, and it is a different kind of evidence. Ours are ISO 9001 (10423Q01965R1M), ISO 14001 (10423E01271R1M) and ISO 45001 (10423S01149R0M), issued by Shandong Seatone International Certification Co., Ltd. under CNAS accreditation. Those references are published so you can check them with the issuing body rather than trusting a scan.

And a COA is not a market approval either. NSF listing covers the United States drinking-water inventory; EU REACH registration covers the European market. Neither transfers to the other, and neither of them is a batch document.

If you want to see the format before ordering, ask. We will send a certificate from a recent batch of the grade you are considering, with the batch reference intact, so you can hand it to your QA department and see whether it answers their questions.