What a certificate of analysis can and cannot tell you

Ask for the certificate, and say which one

Alliance sends a Certificate of Analysis when a customer asks, at no charge. Put the request in the purchase order, and say which document is meant. A sample or typical certificate describes what the product has looked like; a lot certificate reports results for the material being shipped to you. In a records file the two are not interchangeable.

Record what the certificate is expected to contain before it arrives: the analytes, the methods, the units, and the reporting limit for each. A certificate reports what was measured. It makes no statement about anything that was not on the list, and a species below a reporting limit is a limit, not a zero.

• Is the document a typical/sample certificate or a certificate for the shipped lot?
• Which analytes, methods, units and reporting limits does it actually cover?
• Which of your specification limits are not addressed by it at all?

A discharge standard is not a purity specification

40 CFR 433.15 sets pretreatment standards for existing sources in milligrams per liter, as a maximum for any one day and a monthly average: cadmium 0.69 and 0.26, chromium 2.77 and 1.71, copper 3.38 and 2.07, lead 0.69 and 0.43, nickel 3.98 and 2.38, silver 0.43 and 0.24, zinc 2.61 and 1.48, and total cyanide 1.20 and 0.65.

Those are limits on what leaves a plant, measured at a regulated point. They are not limits on what arrives in a drum, and borrowing them as an incoming-material specification is an easy substitution to make and an expensive one to unwind. Incoming limits come from the process specification and from bath control experience. Where the specification names no limit for a species, that gap is a question for the process owner, not a number to lift from an effluent table.

Make the measurement traceable, or say that it is not

NIST describes metrological traceability as a property of a measurement result: the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty. The elements it lists include a clearly defined property, a full description of the measurement system, a stated value with a documented uncertainty evaluation, and a complete specification of the reference at the time of comparison.

That is a usable checklist for reading someone else’s number and for defending your own. Where an element is missing, record it as missing. An undocumented result can still be informative; it should not be filed as though it were traceable.

Every certificate has a revision

NIST certifies and supplies over 1,200 reference materials, and tells users to confirm that the certificate in their possession is current. The same check applies to a supplier document: a certificate describes a state of knowledge on a date, and an old one can be quietly wrong about a current product.

Where an internal bath analysis feeds an acceptance decision, record which reference the analysis was calibrated against and when. A finisher’s own laboratory result is evidence in exactly the way a supplier’s is—as good as the method, the reference and the uncertainty behind it.

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

Revision record

1.0 · September 12, 2026 — Source-based editorial edition. No original testing or product qualification is claimed.

For finishers and their purchasing teams specifying bulk acids, bases and salts. This collection does not design a bath, set an operating concentration, qualify a process, or make a discharge, waste or exposure determination.